Risk factors for respiratory depression and its effect on postoperative pulmonary complications in the PACU: A prospective cohort study

Risk factors for respiratory depression and its effect on postoperative pulmonary complications in the PACU: A prospective cohort study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Risk factors for respiratory depression and its effect on postoperative pulmonary complications in the PACU: A prospective cohort study Dan Wang, Kai Li, Shufang Sun, Qi Chen, Qianyun Pang, Ran An This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6948468/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Respiratory depression (RD) is a frequent postoperative complication in the post-anesthesia care unit (PACU). This prospective cohort study investigated the risk factors for RD and examined its impact on postoperative pulmonary complications (PPCs). Methods Data were collected from June 2022 to August 2023 at a tertiary care Centre. Patients were assigned to RD or non-RD groups based on the occurrence of RD in the PACU, defined as SpO₂ < 90%, respiratory rate < 8/min, apnea ≥ 10 s, or analgesia-sedation mismatch. The primary objective was to identify risk factors for RD in the PACU. Secondary outcomes included the incidence of RD and its effect on PPCs. Results RD was observed in 152 patients (17.4%). Multivariate logistic regression analysis revealed that age ( p = 0.034), American Society of Anesthesiologists (ASA) III classification (P = 0.006), preoperative lung disease ( p < 0.001), preoperative hypoxemia (P = 0.044), preoperative hypercapnia ( p = 0.03), intraoperative hypothermia ( p < 0.001) and PACU rescue opioid analgesics ( p < 0.001) were independent risk factors for RD in the PACU. RD in the PACU was significantly associated with an increased incidence of PPCs (OR = 3.81, 95%CI 1.07 to 13.57, p = 0.044), postoperative pneumonia (OR = 3.00, 95%CI 1.15 to 7.8, p = 0.024), unplanned transfer to ICU (OR = 3.81, 95%CI 1.07 to 13.57, p = 0.039) and prolonged hospital stay (OR = 1.04, 95%CI 1.01 to 1.09, p = 0.033). Conclusion Age, ASA III classification, pre-existing pulmonary disease, hypoxemia, hypercapnia, intraoperative hypothermia, and rescue opioid use in the PACU are independent risk factors for RD. RD in the PACU is associated with increased risk of PPCs and other adverse postoperative outcomes. Trial registry: Chinese Clinical Trial Registry ChiCTR2200061256. Registered on 18 June, 2022. Respiratory depression Risk factors Postoperative pulmonary complications Figures Figure 1 Introduction Post-extubation respiratory depression (RD) is a frequent complication following general anesthesia [ 1 – 3 ]. Ageing, opioid administration, sedative-hypnotic use, and mechanical ventilation are among the factors that can lead to considerable respiratory impairment during recovery, potentially resulting in RD or apnea. Most RD episodes occur within the initial hours post-extubation, typically in the post-anesthesia care unit (PACU). Timely detection of RD is essential to prevent serious outcomes. Previous studies have shown that continuous oximetry improves the detection of post-extubation RD. However, it does not offer an objective evaluation of the severity or pattern of RD [ 4 ]. A large-scale prospective study indicated that combined monitoring of end-tidal carbon dioxide and oxygen saturation is effective in identifying RD in general care settings [ 5 ]. Furthermore, some investigations have adopted continuous monitoring of carbon dioxide and oxygen saturation, integrating them into an “Integrated Pulmonary Index” to detect RD in the PACU [ 5 , 6 ]. Nevertheless, end-expiratory carbon dioxide monitoring can be influenced by several factors that interfere with waveform accuracy, and the integrated pulmonary index is associated with a 60% false-positive rate, which greatly limits its clinical utility [ 7 ]. At present, there are no reliable tools for early identification of patients experiencing RD, highlighting the importance of risk recognition. This study primarily aimed to investigate risk factors for PACU RD using multivariate regression. Additionally, propensity score matching (PSM) was employed to evaluate the effect of PACU RD on postoperative pulmonary complications (PPCs) up to the point of hospital discharge. Materials and methods Study design and participants This prospective cohort study was approved by the ethics committee of Chongqing university cancer hospital (CZLS2022109-A-44) and registered with the Chinese Clinical Trial Registry (ChiCTR2200061256, http://www.chictr.org.cn ). The study was conducted from November 2022 to August 2023 in accordance with the Declaration of Helsinki (2013). Written informed consent was obtained from all participants prior to surgery. Patients aged ≥ 18 years undergoing elective non-cardiac surgery under general anesthesia and admitted to the PACU were eligible for inclusion. Exclusion criteria were preoperative PaO 2 ≤ 60 mmHg, severe hepatic or renal impairment, intraoperative airway injury, bleeding ≥ 1500 ml, or postoperative transfer to the ICU admission. Exposure and Outcomes In the PACU, a nurse anesthetist and an anesthesiologist assessed patients who met inclusion criteria for RD, based on predefined diagnostic criteria, and recorded their findings in the electronic medical record. RD was defined as recurrent postoperative respiratory events, including bradypnea ( 9 seconds observed by nursing staff), oxygen desaturation (< 90% on pulse oximetry while receiving ≤ 4 L/min supplemental oxygen for ≥ 30 seconds), or failure to transition to nasal cannula oxygenation. A mismatch between analgesia and sedation (RASS score − 3 to − 5 with pain score > 5) was also evaluated [ 8 – 10 ]. Chest impedance was used for continuous respiratory rate monitoring following extubation [ 11 , 12 ]. All patients underwent train-of-four ratio (TOFr) monitoring. When TOFr reached ≥ 0.6, neostigmine (1 mg) and atropine (0.5 mg) were administered. Extubation was performed only when TOFr was ≥ 0.9. The primary outcome was identification of risk factors for RD in the PACU. Secondary outcomes included the incidence of PPCs until discharge, unplanned ICU transfers from the PACU, and average hospital stay. PPCs were diagnosed according to European Perioperative Clinical Outcome (EPCO) definitions [ 13 ]. Detailed criteria for PPCs are available in the Appendix. Data collection Two investigators independently collected data using standardized forms. Patient-related variables included sex, age, smoking status, alcohol consumption, BMI, ASA classification, and preoperative comorbidities (hypertension, diabetes, coronary artery disease, stroke, pulmonary disease, hypoxemia, hypercapnia). Intraoperative data obtained from the anesthesia information system included surgery type and duration, hypotension, airway pressure, anesthesia technique, hypothermia, blood loss, fluid volume administered, sufentanil dosage, and timing of the last sufentanil dose. Sample Size The incidence of PPCs was 14.5% in patients with RD and 7.3% in those without, based on previously published data [ 14 ]. With α = 0.05 and β = 0.1, and assuming a 1:1 ratio between exposure and control groups, the required sample size was calculated using PASS 11.0 software (NCSS, LLC, Kaysville, Utah, USA). Allowing for a 15% rate of missing data, the final sample size was determined as N1 = N2 = 448, resulting in a total of 896 participants. Statistical analysis All statistical analyses were performed using R version 4.4.1 (R Foundation for Statistical Computing, Vienna, Austria). The distribution of continuous variables was assessed using the Shapiro–Wilk test and Q–Q plots. Variables following a normal distribution were presented as mean ± standard deviation, while non-normally distributed data were reported as median and interquartile range. Categorical variables were compared using the χ² test or Fisher’s exact test, as appropriate. Continuous variables were analyzed using Student’s t-test or the Wilcoxon rank sum test, depending on distribution. The presence of respiratory depression (RD) in the PACU was treated as the dependent variable. Demographic and clinical variables were considered independent variables. Univariate logistic regression was first used to identify potential predictors. Variables with p > 0.2 in univariate analysis were included in the multivariate logistic regression to identify independent risk factors for PACU RD. A backward selection approach was applied to build the final model. Multivariate results were reported as odds ratios with 95% confidence intervals (CI). To reduce confounding in the analysis of PPCs, propensity score matching was applied using a 1:2 ratio and a greedy matching algorithm with a caliper width of 0.2. The matching variables are listed in Table 1 . Multivariate logistic regression was conducted to evaluate the impact of RD on postoperative outcomes, with findings expressed as odds ratios and 95% CI. The variance inflation factor (VIF) was calculated to assess multicollinearity among independent variables; a VIF > 10 was considered indicative of considerable multicollinearity, and the affected variables were removed from the model. Table 1 Characteristics of patients with RD or without RD in PACU Variables * Before PSM After PSM RD RD Yes (n = 152) No (n = 722) All patients (n = 874) SMD Yes(n = 141) No(n = 232) SMD Age(years) 59.70 ± 10.06 54.97 ± 11.63 55.79 ± 11.51 0.47 59.25 ± 10.18 60.02 ± 10.06 -0.08 Male (%) 61 (40.13) 274 (37.95) 335 (38.33) 0.05 53 (39.01) 111 (47.84) -0.18 BMI (kg/m 2 ) 24.34 ± 3.39 23.49 ± 3.21 23.64 ± 3.26 0.25 24.24 ± 3.36 24.44 ± 3.42 -0.06 ASA classification (%) II 38 (25) 340 (47.09) 378 (43.25) -0.51 37(26.24) 57 (24.57) -0.18 III 114 (75) 381 (52.77) 495 (56.64) 0.51 104(73.36) 175(75.43) 0.18 Ⅳ 0 (0.00) 1 (0.14) 1 (0.11) -0.04 N N N Smoking 17 (11.18) 82 (11.36) 99 (11.33) 0.00 15 (10.64) 32 (13.79) -0.37 Alcohol abuse 15 (9.87) 48 (6.65) 63 (7.21) 0.11 13 (9.22) 12 (5.17) 0.14 Hypertension 40 (26.32) 98 (13.57) 138 (15.79) -0.29 35 (24.82) 62 (26.72) -0.68 CAD 7 (4.61) 20 (2.77) 27 (3.09) 0.89 7 (4.96) 13 (5.6) -0.79 Diabetes 19 (12.50) 47 (6.51) 66 (7.55) 0.18 15 (10.64) 16 (6.9) 0.12 Stroke 14 (9.21) 41 (5.68) 55 (6.29) -0.12 9 (6.38) 18 (7.76) -0.06 Hepatic insufficiency 5 (3.29) 18 (2.49) 23 (2.63) -0.05 9 (3.88) 5 (3.55) 0.018 Hypoproteinemia 3 (1.9) 18 (2.50) 21 (2.41) -0.04 3 (2.13) 11 (4.74) -0.18 Renal insufficiency 4 (2.63) 1 (0.14) 5 (0.57) 0.16 2 (1.42) 0 (0.00) 0.12 Lung diseases 42 (27.63) 58 (8.03) 100 (11.44) -0.44 34 (24.11) 42 (18.1) 0.14 hypoxemia 16 (10.53) 33 (4.57) 49 (5.61) -0.19 14 (9.93) 13 (5.6) 0.14 Hypercapnia 10 (6.58) 13 (1.80) 23 (2.63) -0.19 9 (6.38) 7 (3.02) 0.14 STOP-Bang scores ≥ 3(%) 24 (15.79) 48(6.65) 72 (8.24) 0.25 21 (14.89) 37 (15.95) -0.03 Anesthesia methods (%) -0.22 -0.15 Total intravenous anesthesia 7 (4.61) 66 (9.14) 73 (8.35) 7 (4.96) 19 (8.19) Intravenous-inhalational anesthesia 145 (95.39) 656 (90.86) 801 (91.65) 134 (95.04) 213 (91.81) Intraoperative hypothermia (%) 20 (13.16) 21 (2.91) 41 (4.69) -0.30 17 (12.06) 18 (7.3) 0.13 Intraoperative hypotension (%) 1 (0.66) 18 (2.49) 19 (2.17) 0.23 1 (0.71) 1 (0.43) 0.03 Intraoperative fluid administration (ml) 1800[1500 to 2400] 1900 [1400 to 2400] 1800[1400 to 2400] -0.1 1800 [1400 to 2400] 2000 [1575 to 2400] -0.21 Intraoperative blood loss (ml) 100 [50 to 100] 100[50 to 100] 100[50 to 100] -0.24 100.00 [50 to 100] 50 [50.00 to 100] 0.01 Intraoperative sufentanil consumption(µg) 45[40 to 50] 45.00 (40 to 50) 45[40 to 50) 0.05 45 [40to 50] 45 [40.00, 50] 0.01 Time of last of Sufentanil (min) 35 [25 to 45] 35[30 to 45] 35[25 to 45] 0.02 35[25 to 45] 35[30 to 45] 0.00 Time of last of muscle relaxant (min) 34.5[23 to 41.25) 31 [23 to 41] 32[23 to 41] 0.15 40.00 [30 to 50] 43.00 [32 to 60] 0.13 Post-extubation NRS scores 2[1 to 3] 2[1 to 3] 2[1 to 3] -0.04 2.00 [1 to 3] 2.00 [1 to 3] -0.24 Type of surgery (%) Thoracic surgery 52 (34.21) 256 (35.46) 308 (35.24) -0.03 47 (33.33) 94 (40.52) -0.15 Laparoscopic surgery 70 (46.05) 324 (44.88) 394 (45.08) 0.02 65 (46.10) 92 (39.66) 0.13 Open abdominal surgery 8 (5.26) 39 (5.40) 47 (5.38) -0.01 8 (5.67) 9 (3.88) 0.08 Hepatobiliary surgery 5 (3.29) 33 (4.57) 38 (4.35) -0.07 4 (2.84) 14 (6.03) -0.19 Natural cavity surgery 3 (1.97) 18 (2.49) 21 (2.40) -0.04 3 (2.13) 5 (2.16) -0.00 Head & neck and breast cancer surgery 12 (7.89) 43 (5.96) 55 (6.29) -0.07 12 (8.51) 13 (5.60) 0.10 Orthopedic surgery 2 (1.32) 5 (0.69) 7 (0.80) 0.06 2 (1.42) 4 (1.72) -0.03 Other surgery 1 0 4 (0.55) 4 (0.46) -0.08 0 (0.00) 1 (0.43) -0.08 PCIA (%) 133(87.5) 635(87.95) 768(87.87) -0.01 125 (88.65) 198 (85.34) 0.104 PACU rescue non-opioid analgesics (%) 33(21.71) 144(19.94) 177(20.25) -0.04 26 (18.44) 56 (24.14) -0.147 PACU rescue opioid analgesics (%) 24 (15.79) 17(2.35) 17 (2.35) -0.37 17 (12.06) 16 (6.90) 0.158 Time of surgery (min) 142[110 to 196.25] 156 [120 to 215.75] 155 [116 to 214] -0.16 143 [110 to 197] 156 [127 to 219.25] -0.19 Note: Data were presented as mean (SD), median [IQR], or n (%); RD: Respiratory depression; PACU: Post-anesthesia care unit; PSM: Propensity score matched; BMI: Body mass index; ASA: American Society of Anesthesiologists; SMD: Standard mean difference; CAD: Coronary artery disease; PCIA: patient-controlled intravenous analgesia; * Definition of other surgery was showed appendix (Table 1 . Definition of variables) Results During the study period, 896 patients were enrolled in the prospective cohort. Of these, seven were transferred to the ICU postoperatively, eight experienced intraoperative hemorrhage exceeding 1500 ml, and seven had incomplete data. A total of 874 patients were therefore included in the final analysis. Figure 1 displays the participant selection process. In the PACU, 152 patients (17.4%) developed RD. The median age of the all patients was 55.79 years (standard deviation: 11.51), and 335 patients (38.33%) were male. In terms of ASA classification, 378 patients (43.25%) were ASA II and 495 patients (56.64%) were ASA III. The most frequent types of surgery were laparoscopic (394 patients, 45.08%) and thoracoscopic (308 patients, 35.24%). Baseline characteristics are presented in Table 1 . Risk factors for the PACU Multivariate logistic regression identified the following independent risk factors for RD in the PACU: age (OR 1.02, 95% CI 1.0 to 1.04, p = 0.034), ASA class III (OR 1.97, 95% CI 1.21 to 3.2, p = 0.006), preoperative lung disease (OR 4.04, 95% CI 2.42 to 6.72, p < 0.001), preoperative hypoxemia (OR 2.03, 95% CI 1.02 to 4.06, p = 0.044), preoperative hypercapnia (OR 3.03, 95% CI 2.93 to 7.75, p = 0.03), intraoperative hypothermia (OR 8.61, 95% CI 4.12 to 17.97, p < 0.001), and rescue opioid use in the PACU (OR 7.19, 95% CI 3.4 to 15.23, p < 0.001). These associations are summarized in Table 2 . VIF analysis indicated no multicollinearity among the independent variables; detailed results are provided in the Appendix. Table 2 Factors associated with RD in PACU Univariable logistic regression Multivariable logistic regression Variables OR (95% CI) P OR (95% CI) P Age 1.04 (1.02 to 1.06) < .001 1.02 (1.0 to 1.04) 0.034 BMI 1.08 (1.03 to 1.14) 0.004 1.05(0.99 to 1.13) 0.135 Male 0.91 (0.64 to 1.30) 0.615 STOP-Bang scores ≥ 3 2.63 (1.56 to 4.45) < .001 1.70 (0.92 to 3.16) 0.091 ASA classification III 2.68 (1.80 to 3.97) < .001 1.97 (1.21 to 3.2) 0.006 Ⅳ 0.00 (0.00 to Inf) 0.983 Smoking 0.98 (0.56 to 1.71) 0.951 Alcohol abuse 1.54 (0.84 to 2.82) 0.166 Preoperative hypertension 2.27 (1.50 to 3.46) < .001 1.66 (0.98 to 2.73) 0.078 Preoperative CAD 1.69 (0.70 to 4.08) 0.24 Preoperative diabetes mellitus 2.05 (1.17 to 3.61) 0.013 1.36 (0.70 to 2.64) 0.363 Preoperative stroke 1.69 (0.89 to 3.18) 0.107 0.77 (0.37 to 1.62) 0.494 Preoperative lung diseases 4.37 (2.80 to 6.82) < .001 4.04 (2.42 to 6.72) < .001 Preoperative hypoxemia 2.46 (1.32 to 4.59) 0.005 2.03 (1.02 to 4.06) 0.044 Preoperative hypercapnia 3.84 (1.65 to 8.93) 0.002 3.03 (2.93 to 7.75) 0.03 Preoperative hepatic insufficiency 1.33 (0.49 to 3.64) 0.578 Preoperative hypoproteinemia 0.79 (0.23 to 2.70) 0.703 Preoperative renal insufficiency 19.49 (2.16 to 175.40) 0.008 8.04 (0.59 to 109.96) 0.118 Anesthesia method 2.08 (0.94 to 4.64) 0.072 Intraoperative hypothermia 5.06 (2.67 to 9.59) < .001 8.61 (4.12 to 17.97) < .001 Intraoperative hypotension 0.26 (0.03 to 1.95) 0.19 0.22 (0.03 to 1.83) 0.162 Intraoperative dose of sufentanil 1.01 (0.99 to 1.03) 0.606 Time of last of sufentanil 1.00 (0.99 to 1.01) 0.712 Time of last of muscle relaxant 1.01 (1.00 to 1.02) 0.186 Intraoperative fluids 1.00 (1.00 to 1.00) 0.362 Intraoperative bleeding 1.00 (1.00 to 1.00) 0.096 1.00 (1.00 to 1.00) 0.124 Post-extubation NRS scores 0.98 (0.87 to 1.10) 0.707 PCIA 0.96 (0.56 ~ 1.63) 0.877 PACU rescue non-opioid analgesics 1.11 (0.73 ~ 1.71) 0.623 PACU rescue opioid analgesics 7.78 (4.06 ~ 14.88) < .001 7.19 (3.40 ~ 15.23) < .001 Type of surgery 1.02 (0.91 to 1.15) 0.728 Time of surgery 1.00 (1.00 to 1.00) 0.917 Note: RD: Respiratory depression; PACU: Post-anesthesia care unit; BMI: Body mass index; ASA: American Society of Anesthesiologists; PCIA: Patient-controlled intravenous analgesia; NRS: Numerical rating scale; OR: odds ratio; CI: Confidence interval Effects of RD in the PACU after PSM In this cohort study, baseline characteristics were well balanced between the exposure groups after PSM was applied to adjust for relevant variables. A total of 141 patients experienced RD in the PACU, while 232 patients did not. Table 1 presents the baseline characteristics of the matched study population. Multivariate logistic regression analysis showed that RD in the PACU significantly increased the risk of PPCs (OR 3.26, 95% CI 1.03 to 10.27; p = 0.044), postoperative pneumonia (OR 3.00, 95% CI 1.15 to 7.8; p = 0.024), unplanned ICU transfer (OR 3.81, 95% CI 1.07 to 13.57; p = 0.039), and longer average hospital stay (OR 1.04, 95% CI 1.01 to 1.09; p = 0.033). The incidence of postoperative pneumothorax was low. Before PSM, three cases occurred in the RD group and five in the non-RD group. After PSM, no cases were recorded in the RD group, and one case remained in the non-RD group. No statistical analysis was performed for postoperative pneumothorax due to the small numbers. Table 3 shows the impact of PACU RD on postoperative outcomes. VIF analysis indicated no multicollinearity among independent variables, and the corresponding data are provided in the Appendix. Distributional balance plots for distance and covariates are also included in the Appendix. Table 3 Effect of RD in PACU on PPCs Outcomes RD Univariable logistic regression Multivariable logistic regression Yes(n = 141) No(n = 232) OR (95%CI), P value OR (95%CI), P value PPCs (%) 66 (46.81) 32 (13.79) 5.50 (3.34 to 9.06), < .001 3.26 (1.03 to 10.27), 0.044 Postoperative pneumonia (%) 47 (33.33) 15 (6.47) 7.23 (3.85 to 13.58), < .001 3.00 (1.15 to 7.80), 0.024 Postoperative hypoxemia (%) 6 (4.26) 3 (1.29) 3.39 (0.83 to 13.79), 0.088 1.50 (0.30 to 7.56), 0.624 Pleural effusion (%) 30 (21.28) 23 (9.91) 2.46 (1.36 to 4.43), 0.003 0.33 (0.11 to 1.02), 0.055 Atelectasis (%) 53 (37.59) 24 (10.34) 5.22 (3.03 to 8.98), < .001 1.84 (0.69 to 4.90), 0.224 Unplanned ICU admission (%) 10 (7.09) 4 (1.72) 4.35 (1.34 to 14.15), 0.015 3.81 (1.07 to 13.57), 0.039 Average hospital stays (days) 9[ 7 , 12 ] 8.00 [ 5 , 11 ] 1.06 (1.02 to 1.1), < .001 1.04 (1.01 to 1.09), 0.033 Notes: Data were presented as median [IQR], or n (%); RD: Respiratory depression; PACU: Post-anesthesia care unit; PPCs: Postoperative pulmonary complications; ICU: Intensive care unit; OR: odds ratio; CI: Confidence interval Discussion In this study, the incidence of RD in the PACU was approximately 17.4%. Independent risk factors identified were age, ASA III classification, preoperative pulmonary disease, hypoxemia, hypercapnia, intraoperative hypothermia, and the use of rescue opioids in the PACU. RD in the PACU significantly increased the risk of PPCs, unplanned ICU transfer from the PACU, and extended hospital stay, but it did not affect the rates of postoperative hypoxemia, pleural effusion, or atelectasis by the time of discharge. The primary mechanisms contributing to RD in the PACU are insufficient ventilation and compromised gas exchange. Central respiratory depression caused by opioids and sedatives is the leading cause, followed by effects from mechanical ventilation and postoperative atelectasis, particularly in thoracic or upper abdominal procedures. These factors limit effective gas exchange. Chun et al. found that 78% of patients requiring intervention were identified through carbon dioxide monitoring in the PACU, while only 6% were detected through clinical assessment alone [ 15 ]. RD is often episodic, with normal breathing intervals, and may resemble simple drowsiness [ 16 ]. Additionally, suboptimal allocation of PACU resources contributes to under recognition. As such, identifying patients at higher risk for RD remains essential. The PRODIGY trial listed several risk factors for postoperative RD, including age > 60 years, sex, opioid naivety, sleep disorders, chronic heart failure, and sleep-disordered breathing [ 5 ]. However, these findings primarily focused on the role of opioid use after surgery. Other studies have shown that factors such as low BMI, preoperative opioid or gabapentin use, high intraoperative doses of opioids or midazolam, and the use of isoflurane can increase the likelihood of RD following extubation in the PACU, particularly in patients undergoing total joint replacement or laparoscopic surgery [ 17 – 19 ]. Upper abdominal and thoracic surgeries, which more directly affect respiratory function, are associated with higher rates of PPCs [ 20 ]. Ageing increases patient sensitivity to opioids and anesthetics, thereby raising the risk of RD. We found that preoperative lung disease was an independent risk factor for RD in the PACU. This may be related to worsened atelectasis and increased intrapulmonary shunting caused by underlying lung pathology, as well as renal impairment that delays drug clearance. Additionally, preoperative hypoxemia and hypercapnia were both significantly associated with elevated RD risk. Reduced overall health status and reduced cardiopulmonary reserve, reflected in older age and ASA class III, also contributed to RD occurrence in the PACU. These findings align with those reported by Khanna et al. [ 5 ]. Inadequate intraoperative pain control can result in severe post-extubation discomfort, prompting the need for additional opioid administration in the PACU, which further increases RD risk. Intraoperative hypothermia is commonly observed in surgical patients and can impair drug metabolism, trigger shivering, and delay PACU discharge [ 21 – 23 ]. This study is the first, to our knowledge, to identify intraoperative hypothermia as an independent risk factor for RD in the PACU. The STOP-Bang questionnaire is widely used to assess preoperative risk for obstructive sleep apnea (OSA) [ 24 ], but its value in predicting postoperative hypoxemia has been questioned [ 25 ]. Our findings support this, showing that a STOP-Bang score ≥ 3 was not an independent predictor of RD in the PACU. An association was observed between RD in the PACU and subsequent respiratory complications in the general care unit. Gali et al. reported that patients who developed RD in the PACU were more likely to experience postoperative respiratory issues [ 26 ]. Additionally, the use of naloxone in the PACU to reverse opioid-induced RD may significantly increase the risk of postoperative complications [ 18 , 27 ]. Our findings showed that RD in the PACU significantly increases the incidence of PPCs and pneumonia. Pulmonary atelectasis and pneumonia, both common postoperative outcomes linked to surgery, mechanical ventilation, and patient-initiated extubation, contribute to RD in the PACU and may continue to affect respiratory status beyond the PACU. Our study also demonstrated that RD in the PACU led to higher rates of unplanned ICU transfer and longer hospital stays. However, we did not observe an increased risk of other pulmonary complications. While the cohort included low-risk surgical patients with a low overall incidence of postoperative pleural effusion and hypoxaemia, some data were missing after PSM, which limits interpretation. These findings warrant further investigation in studies with larger sample sizes. Unlike prior studies focused on postoperative opioid-induced RD, our study specifically evaluated low-risk surgical patients, who are often overlooked in PACU monitoring. In the PRODIGY trial, OSA and heart failure were identified as risk factors for opioid-induced RD [ 5 ]. In our study, however, the number of patients with a preoperative diagnosis of OSA (n = 2) or heart failure (n = 3) was too small to support statistical analysis. Neuromuscular blocking agents are another possible contributor to RD in the PACU. However, we found no significant association between their use and RD. All patients in our study underwent TOFr monitoring, received appropriate reversal agents, and were extubated only after the TOF ratio exceeded 0.9. The limitations of this study are as follows: although previous research has shown that RD in the PACU increases the risk of subsequent postoperative RD, we did not evaluate postoperative RD beyond the PACU due to constraints in personnel and monitoring equipment. Additionally, our study did not examine long-term postoperative mortality or complications such as cerebral infarction, cardiac events, or infections. As a single-centre study, the sample size was limited and may not be representative of broader populations. Conclusion Our findings indicate that age, ASA class III, preoperative pulmonary disease, hypoxemia, hypercapnia, intraoperative hypothermia, and the use of rescue opioids in the PACU are independent risk factors for RD. RD in the PACU significantly increases the incidence of PPCs, postoperative pneumonia, unplanned ICU transfer from the PACU, and prolongs hospital stay. Patients presenting with these risk factors should receive careful monitoring in the PACU to help prevent RD, lower the risk of complications, and improve overall outcomes. Declarations Acknowledgments The authors have no acknowledgements to report. Authors contributions Dan Wang: Data curation, Visualization, Investigation, Writing-original draft; Kai Li: Data curation, Visualization, Writing-original draft; Shufang Sun: Data curation, Methodology, Formal analysis, Software; Qi Chen: Software, Validation, Writing-original draft; Qianyun Pang: Conceptualization, Methodology, Writing-review& editing; Ran An: Conceptualization, Methodology, Supervision, Writing-review& editing. All authors have read and approved the final version of the manuscript. Funding This work was supported by the key research and development program of Chongqing Bureau of Science and Technology (cstc2020jscx-dxwtBX0010) and Chongqing Shapingba District Joint Medical Research Project of Science and Health (No.2024SQKWLHMS006) Data availability De-identified data may be requested with reasonable justification from the authors (email to the corresponding author) and will be shared after approval, as per the authors’ Institution’s policy. Ethics approval and informed consent Ethical approval for this study was granted by the Ethics Committee of the Chongqing University Cancer Hospital (CZLS2022109-A-44). All participants and their parents provided written informed consent, and this study was conducted in accordance with the Declaration of Helsinki. Consent for publication Not applicable. Competing interests The authors declare no competing interests. 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Overdyk FJ, Carter R, Maddox RR, Callura J, Herrin AE, Henriquez C: Continuous Oximetry/Capnometry Monitoring Reveals Frequent Desaturation and Bradypnea During Patient-Controlled Analgesia . Anesthesia & Analgesia 2007, 105 (2):412-418. Khanna AK, Bergese SD, Jungquist CR, Morimatsu H, Uezono S, Lee S, Ti LK, Urman RD, McIntyre R, Tornero C et al : Prediction of Opioid-Induced Respiratory Depression on Inpatient Wards Using Continuous Capnography and Oximetry: An International Prospective, Observational Trial . Anesthesia & Analgesia 2020, 131 (4):1012-1024. Ronen M, Weissbrod R, Overdyk FJ, Ajizian S: Smart respiratory monitoring: clinical development and validation of the IPI™ (Integrated Pulmonary Index) algorithm . Journal of Clinical Monitoring and Computing 2016, 31 (2):435-442. Practice Guidelines for the Prevention, Detection, and Management of Respiratory Depression Associated with Neuraxial Opioid Administration . Anesthesiology 2016, 124 (3):535-552. Sessler CN, Gosnell MS, Grap MJ, Brophy GM, O'Neal PV, Keane KA, Tesoro EP, Elswick RK: The Richmond Agitation–Sedation Scale . American Journal of Respiratory and Critical Care Medicine 2002, 166 (10):1338-1344. Vasilevskis EE, Morandi A, Boehm L, Pandharipande PP, Girard TD, Jackson JC, Thompson JL, Shintani A, Gordon SM, Pun BT et al : Delirium and Sedation Recognition Using Validated Instruments: Reliability of Bedside Intensive Care Unit Nursing Assessments from 2007 to 2010 . Journal of the American Geriatrics Society 2011, 59 (s2):S249-255. Laporta ML, Sprung J, Weingarten TN: Respiratory depression in the post-anesthesia care unit: Mayo Clinic experience . Bosnian Journal of Basic Medical Sciences 2020, 21 (2):221-228. Frasca D, Geraud L, Charriere JM, Debaene B, Mimoz O: Comparison of acoustic and impedance methods with mask capnometry to assess respiration rate in obese patients recovering from general anaesthesia . Anaesthesia 2015, 70 (1):26-31. Bawua LK, Miaskowski C, Suba S, Badilini F, Rodway GW, Hu X, Pelter MM: Thoracic Impedance Pneumography-Derived Respiratory Alarms and Associated Patient Characteristics . American journal of critical care : an official publication, American Association of Critical-Care Nurses 2022, 31 (5):355-365. Jammer I, Wickboldt N, Sander M, Smith A, Schultz MJ, Pelosi P, Leva B, Rhodes A, Hoeft A, Walder B et al : Standards for definitions and use of outcome measures for clinical effectiveness research in perioperative medicine: European Perioperative Clinical Outcome (EPCO) definitions: a statement from the ESA-ESICM joint taskforce on perioperative outcome measures . Eur J Anaesthesiol 2015, 32 (2):88-105. Weingarten TN, Herasevich V, McGlinch MC, Beatty NC, Christensen ED, Hannifan SK, Koenig AE, Klanke J, Zhu X, Gali B et al : Predictors of Delayed Postoperative Respiratory Depression Assessed from Naloxone Administration . Anesthesia & Analgesia 2015, 121 (2):422-429. Chung F, Wong J, Mestek ML, Niebel KH, Lichtenthal P: Characterization of respiratory compromise and the potential clinical utility of capnography in the post-anesthesia care unit: a blinded observational trial . Journal of Clinical Monitoring and Computing 2019, 34 (3):541-551. Lee LA, Caplan RA, Stephens LS, Posner KL, Terman GW, Voepel-Lewis T, Domino KB: Postoperative Opioid-induced Respiratory Depression . Anesthesiology 2015, 122 (3):659-665. Cavalcante AN, Sprung J, Schroeder DR, Weingarten TN: Multimodal Analgesic Therapy With Gabapentin and Its Association With Postoperative Respiratory Depression . Anesthesia & Analgesia 2017, 125 (1):141-146. Weingarten TN, Bergan TS, Narr BJ, Schroeder DR, Sprung J: Effects of changes in intraoperative management on recovery from anesthesia: a review of practice improvement initiative . BMC Anesthesiology 2015, 15 (1):54. Cavalcante AN, Gurrieri C, Sprung J, Schroeder DR, Weingarten TN: Isoflurane and postoperative respiratory depression following laparoscopic surgery: A retrospective propensity matched analysis . Bosnian Journal of Basic Medical Sciences 2017, 18 (1):95-100. Qaseem A, Snow V, Fitterman N, Hornbake ER, Lawrence VA, Smetana GW, Weiss K, Owens DK: Risk Assessment for and Strategies To Reduce Perioperative Pulmonary Complications for Patients Undergoing Noncardiothoracic Surgery: A Guideline from the American College of Physicians . Annals of Internal Medicine 2006, 144 (8):575-580. Sessler DI: Mild perioperative hypothermia . N Engl J Med 1997, 336 (24):1730-1737. Heier T, Caldwell JE, Sessler DI, Miller RD: Mild intraoperative hypothermia increases duration of action and spontaneous recovery of vecuronium blockade during nitrous oxide-isoflurane anesthesia in humans . Anesthesiology 1991, 74 (5):815-819. Lenhardt R, Marker E, Goll V, Tschernich H, Kurz A, Sessler DI, Narzt E, Lackner F: Mild intraoperative hypothermia prolongs postanesthetic recovery . Anesthesiology 1997, 87 (6):1318-1323. Nagappa M, Patra J, Wong J, Subramani Y, Singh M, Ho G, Wong DT, Chung F: Association of STOP-Bang Questionnaire as a Screening Tool for Sleep Apnea and Postoperative Complications: A Systematic Review and Bayesian Meta-analysis of Prospective and Retrospective Cohort Studies . Anesthesia and analgesia 2017, 125 (4):1301-1308. Khanna AK, Sessler DI, Sun Z, Naylor AJ, You J, Hesler BD, Kurz A, Devereaux PJ, Saager L: Using the STOP-BANG questionnaire to predict hypoxaemia in patients recovering from noncardiac surgery: a prospective cohort analysis . British journal of anaesthesia 2016, 116 (5):632-640. Gali B, Whalen FX, Schroeder DR, Gay PC, Plevak DJ: Identification of patients at risk for postoperative respiratory complications using a preoperative obstructive sleep apnea screening tool and postanesthesia care assessment . Anesthesiology 2009, 110 (4):869-877. Deljou A, Hedrick SJ, Portner ER, Schroeder DR, Hooten WM, Sprung J, Weingarten TN: Pattern of perioperative gabapentinoid use and risk for postoperative naloxone administration . British journal of anaesthesia 2018, 120 (4):798-806. Additional Declarations No competing interests reported. Supplementary Files Appendix.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6948468","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":485959194,"identity":"0d3a6c07-d65d-4e85-b7dc-ae325330dc13","order_by":0,"name":"Dan Wang","email":"","orcid":"","institution":"Chongqing University Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Dan","middleName":"","lastName":"Wang","suffix":""},{"id":485959195,"identity":"b966fd6e-7a6f-452b-a8af-860b6de10647","order_by":1,"name":"Kai Li","email":"","orcid":"","institution":"Jiulongpo Hospital， Chongqing University of Chinese Medicine","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Li","suffix":""},{"id":485959196,"identity":"5c660dbb-b8ce-4b43-a585-3f8227025a53","order_by":2,"name":"Shufang Sun","email":"","orcid":"","institution":"Chongqing University Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Shufang","middleName":"","lastName":"Sun","suffix":""},{"id":485959197,"identity":"c582ab8e-f505-4ae6-94a2-08c6768d33fd","order_by":3,"name":"Qi Chen","email":"","orcid":"","institution":"Chongqing University Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Qi","middleName":"","lastName":"Chen","suffix":""},{"id":485959198,"identity":"b561ff05-6587-4a0a-b4a5-3b36ce2bfed3","order_by":4,"name":"Qianyun Pang","email":"","orcid":"","institution":"Chongqing University Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Qianyun","middleName":"","lastName":"Pang","suffix":""},{"id":485959199,"identity":"95e05293-f0e7-4eaa-8e9c-7c43d174624a","order_by":5,"name":"Ran An","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAv0lEQVRIiWNgGAWjYNACAwkeNvbGxocfiNdSYCPDx3O42ViCeC0f0mzkJNLbBHiIUcw/u/fh5wKDwzxskg/bGCQY7OR0Gwhokbhz3Fh6BkiLdGLbgwKGZGOzA4SsuZHGIM0D0dJuIMFwIHEbIS3yN9KYf4O1SB5sk+AhRovBjTQ2oC1pPGwSjERqMQRqseYxsOFh40kEBrIBEX6RAzrsNs8fCXv59uMPH36osJMj7H00d5KmfBSMglEwCkYBDgAALXw5cesMoHoAAAAASUVORK5CYII=","orcid":"","institution":"Chongqing University Cancer Hospital","correspondingAuthor":true,"prefix":"","firstName":"Ran","middleName":"","lastName":"An","suffix":""}],"badges":[],"createdAt":"2025-06-22 08:38:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6948468/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6948468/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":87045013,"identity":"6690153c-e07a-4036-bb8f-efc123b16b42","added_by":"auto","created_at":"2025-07-18 14:27:17","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":262706,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version\u003c/p\u003e","description":"","filename":"Figure1.Processofselectingtheresearchsample.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6948468/v1/f774b134145c43890c71dbb8.jpg"},{"id":87047541,"identity":"ae0a9367-ac38-420a-97dc-a9791a22bf8f","added_by":"auto","created_at":"2025-07-18 14:43:21","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2796945,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6948468/v1/a4815474-5ca6-46d9-af30-c02722ff0d36.pdf"},{"id":87042541,"identity":"c1f6b18a-eeb7-4e73-961c-176ff21cdac4","added_by":"auto","created_at":"2025-07-18 14:11:17","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":154939,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix.docx","url":"https://assets-eu.researchsquare.com/files/rs-6948468/v1/a271b32e6c42cffad72fc1a0.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Risk factors for respiratory depression and its effect on postoperative pulmonary complications in the PACU: A prospective cohort study","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePost-extubation respiratory depression (RD) is a frequent complication following general anesthesia [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Ageing, opioid administration, sedative-hypnotic use, and mechanical ventilation are among the factors that can lead to considerable respiratory impairment during recovery, potentially resulting in RD or apnea. Most RD episodes occur within the initial hours post-extubation, typically in the post-anesthesia care unit (PACU). Timely detection of RD is essential to prevent serious outcomes.\u003c/p\u003e\u003cp\u003ePrevious studies have shown that continuous oximetry improves the detection of post-extubation RD. However, it does not offer an objective evaluation of the severity or pattern of RD [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. A large-scale prospective study indicated that combined monitoring of end-tidal carbon dioxide and oxygen saturation is effective in identifying RD in general care settings [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Furthermore, some investigations have adopted continuous monitoring of carbon dioxide and oxygen saturation, integrating them into an \u0026ldquo;Integrated Pulmonary Index\u0026rdquo; to detect RD in the PACU [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Nevertheless, end-expiratory carbon dioxide monitoring can be influenced by several factors that interfere with waveform accuracy, and the integrated pulmonary index is associated with a 60% false-positive rate, which greatly limits its clinical utility [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAt present, there are no reliable tools for early identification of patients experiencing RD, highlighting the importance of risk recognition. This study primarily aimed to investigate risk factors for PACU RD using multivariate regression. Additionally, propensity score matching (PSM) was employed to evaluate the effect of PACU RD on postoperative pulmonary complications (PPCs) up to the point of hospital discharge.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy design and participants\u003c/h2\u003e\u003cp\u003eThis prospective cohort study was approved by the ethics committee of Chongqing university cancer hospital (CZLS2022109-A-44) and registered with the Chinese Clinical Trial Registry (ChiCTR2200061256, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.chictr.org.cn\u003c/span\u003e\u003cspan address=\"http://www.chictr.org.cn\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). The study was conducted from November 2022 to August 2023 in accordance with the Declaration of Helsinki (2013). Written informed consent was obtained from all participants prior to surgery.\u003c/p\u003e\u003cp\u003ePatients aged\u0026thinsp;\u0026ge;\u0026thinsp;18 years undergoing elective non-cardiac surgery under general anesthesia and admitted to the PACU were eligible for inclusion. Exclusion criteria were preoperative PaO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;\u0026le;\u0026thinsp;60 mmHg, severe hepatic or renal impairment, intraoperative airway injury, bleeding\u0026thinsp;\u0026ge;\u0026thinsp;1500 ml, or postoperative transfer to the ICU admission.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eExposure and Outcomes\u003c/h3\u003e\n\u003cp\u003eIn the PACU, a nurse anesthetist and an anesthesiologist assessed patients who met inclusion criteria for RD, based on predefined diagnostic criteria, and recorded their findings in the electronic medical record. RD was defined as recurrent postoperative respiratory events, including bradypnea (\u0026lt;\u0026thinsp;8 breaths/min), apnea (\u0026gt;\u0026thinsp;9 seconds observed by nursing staff), oxygen desaturation (\u0026lt;\u0026thinsp;90% on pulse oximetry while receiving\u0026thinsp;\u0026le;\u0026thinsp;4 L/min supplemental oxygen for \u0026ge;\u0026thinsp;30 seconds), or failure to transition to nasal cannula oxygenation. A mismatch between analgesia and sedation (RASS score \u0026minus;\u0026thinsp;3 to \u0026minus;\u0026thinsp;5 with pain score\u0026thinsp;\u0026gt;\u0026thinsp;5) was also evaluated [\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Chest impedance was used for continuous respiratory rate monitoring following extubation [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. All patients underwent train-of-four ratio (TOFr) monitoring. When TOFr reached\u0026thinsp;\u0026ge;\u0026thinsp;0.6, neostigmine (1 mg) and atropine (0.5 mg) were administered. Extubation was performed only when TOFr was \u0026ge;\u0026thinsp;0.9.\u003c/p\u003e\u003cp\u003eThe primary outcome was identification of risk factors for RD in the PACU. Secondary outcomes included the incidence of PPCs until discharge, unplanned ICU transfers from the PACU, and average hospital stay. PPCs were diagnosed according to European Perioperative Clinical Outcome (EPCO) definitions [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Detailed criteria for PPCs are available in the Appendix.\u003c/p\u003e\n\u003ch3\u003eData collection\u003c/h3\u003e\n\u003cp\u003eTwo investigators independently collected data using standardized forms. Patient-related variables included sex, age, smoking status, alcohol consumption, BMI, ASA classification, and preoperative comorbidities (hypertension, diabetes, coronary artery disease, stroke, pulmonary disease, hypoxemia, hypercapnia). Intraoperative data obtained from the anesthesia information system included surgery type and duration, hypotension, airway pressure, anesthesia technique, hypothermia, blood loss, fluid volume administered, sufentanil dosage, and timing of the last sufentanil dose.\u003c/p\u003e\n\u003ch3\u003eSample Size\u003c/h3\u003e\n\u003cp\u003eThe incidence of PPCs was 14.5% in patients with RD and 7.3% in those without, based on previously published data [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. With α\u0026thinsp;=\u0026thinsp;0.05 and β\u0026thinsp;=\u0026thinsp;0.1, and assuming a 1:1 ratio between exposure and control groups, the required sample size was calculated using PASS 11.0 software (NCSS, LLC, Kaysville, Utah, USA). Allowing for a 15% rate of missing data, the final sample size was determined as N1\u0026thinsp;=\u0026thinsp;N2\u0026thinsp;=\u0026thinsp;448, resulting in a total of 896 participants.\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eAll statistical analyses were performed using R version 4.4.1 (R Foundation for Statistical Computing, Vienna, Austria). The distribution of continuous variables was assessed using the Shapiro\u0026ndash;Wilk test and Q\u0026ndash;Q plots. Variables following a normal distribution were presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation, while non-normally distributed data were reported as median and interquartile range. Categorical variables were compared using the χ\u0026sup2; test or Fisher\u0026rsquo;s exact test, as appropriate. Continuous variables were analyzed using Student\u0026rsquo;s t-test or the Wilcoxon rank sum test, depending on distribution.\u003c/p\u003e\u003cp\u003eThe presence of respiratory depression (RD) in the PACU was treated as the dependent variable. Demographic and clinical variables were considered independent variables. Univariate logistic regression was first used to identify potential predictors. Variables with \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.2 in univariate analysis were included in the multivariate logistic regression to identify independent risk factors for PACU RD. A backward selection approach was applied to build the final model. Multivariate results were reported as odds ratios with 95% confidence intervals (CI).\u003c/p\u003e\u003cp\u003eTo reduce confounding in the analysis of PPCs, propensity score matching was applied using a 1:2 ratio and a greedy matching algorithm with a caliper width of 0.2. The matching variables are listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Multivariate logistic regression was conducted to evaluate the impact of RD on postoperative outcomes, with findings expressed as odds ratios and 95% CI. The variance inflation factor (VIF) was calculated to assess multicollinearity among independent variables; a VIF\u0026thinsp;\u0026gt;\u0026thinsp;10 was considered indicative of considerable multicollinearity, and the affected variables were removed from the model.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCharacteristics of patients with RD or without RD in PACU\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003eBefore PSM\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c9\" namest=\"c7\"\u003e\u003cp\u003eAfter PSM\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eRD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e\u003cp\u003eRD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes (n\u0026thinsp;=\u0026thinsp;152)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNo (n\u0026thinsp;=\u0026thinsp;722)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAll patients (n\u0026thinsp;=\u0026thinsp;874)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eSMD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eYes(n\u0026thinsp;=\u0026thinsp;141)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNo(n\u0026thinsp;=\u0026thinsp;232)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eSMD\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge(years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e59.70\u0026thinsp;\u0026plusmn;\u0026thinsp;10.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e54.97\u0026thinsp;\u0026plusmn;\u0026thinsp;11.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e55.79\u0026thinsp;\u0026plusmn;\u0026thinsp;11.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e59.25\u0026thinsp;\u0026plusmn;\u0026thinsp;10.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e60.02\u0026thinsp;\u0026plusmn;\u0026thinsp;10.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e61 (40.13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e274 (37.95)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e335 (38.33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e53 (39.01)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e111 (47.84)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24.34\u0026thinsp;\u0026plusmn;\u0026thinsp;3.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.49\u0026thinsp;\u0026plusmn;\u0026thinsp;3.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e23.64\u0026thinsp;\u0026plusmn;\u0026thinsp;3.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e24.24\u0026thinsp;\u0026plusmn;\u0026thinsp;3.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e24.44\u0026thinsp;\u0026plusmn;\u0026thinsp;3.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.06\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eASA classification (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eII\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e38 (25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e340 (47.09)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e378 (43.25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e37(26.24)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e57 (24.57)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIII\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e114 (75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e381 (52.77)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e495 (56.64)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e104(73.36)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e175(75.43)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eⅣ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1 (0.14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1 (0.11)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eN\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eN\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eN\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSmoking\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e17 (11.18)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e82 (11.36)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e99 (11.33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15 (10.64)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e32 (13.79)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlcohol abuse\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15 (9.87)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e48 (6.65)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e63 (7.21)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e13 (9.22)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e12 (5.17)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHypertension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e40 (26.32)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e98 (13.57)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e138 (15.79)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e35 (24.82)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e62 (26.72)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.68\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCAD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (4.61)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20 (2.77)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e27 (3.09)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e7 (4.96)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e13 (5.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.79\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e19 (12.50)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e47 (6.51)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e66 (7.55)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15 (10.64)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e16 (6.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStroke\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14 (9.21)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e41 (5.68)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e55 (6.29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9 (6.38)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e18 (7.76)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.06\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHepatic insufficiency\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5 (3.29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (2.49)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e23 (2.63)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9 (3.88)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e5 (3.55)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.018\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHypoproteinemia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 (1.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (2.50)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21 (2.41)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e3 (2.13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e11 (4.74)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRenal insufficiency\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (2.63)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1 (0.14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5 (0.57)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2 (1.42)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0 (0.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLung diseases\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e42 (27.63)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e58 (8.03)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e100 (11.44)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e34 (24.11)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e42 (18.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ehypoxemia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (10.53)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33 (4.57)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e49 (5.61)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e14 (9.93)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e13 (5.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHypercapnia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 (6.58)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e13 (1.80)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e23 (2.63)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9 (6.38)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e7 (3.02)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSTOP-Bang scores\u0026thinsp;\u0026ge;\u0026thinsp;3(%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24 (15.79)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e48(6.65)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e72 (8.24)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e21 (14.89)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e37 (15.95)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnesthesia methods (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal intravenous anesthesia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (4.61)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e66 (9.14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e73 (8.35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e7 (4.96)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e19 (8.19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntravenous-inhalational anesthesia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e145 (95.39)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e656 (90.86)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e801 (91.65)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e134 (95.04)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e213 (91.81)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative hypothermia (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e20 (13.16)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21 (2.91)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e41 (4.69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e17 (12.06)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e18 (7.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative hypotension (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (0.66)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (2.49)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e19 (2.17)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1 (0.71)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1 (0.43)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative fluid administration (ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1800[1500 to 2400]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1900 [1400 to 2400]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1800[1400 to 2400]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1800 [1400 to 2400]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e2000 [1575 to 2400]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.21\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative blood loss (ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e100 [50 to 100]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100[50 to 100]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e100[50 to 100]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e100.00 [50 to 100]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e50 [50.00 to 100]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative sufentanil consumption(\u0026micro;g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e45[40 to 50]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e45.00 (40 to 50)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e45[40 to 50)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e45 [40to 50]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e45 [40.00, 50]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of last of Sufentanil (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35 [25 to 45]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35[30 to 45]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e35[25 to 45]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e35[25 to 45]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e35[30 to 45]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of last of muscle relaxant (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e34.5[23 to 41.25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31 [23 to 41]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e32[23 to 41]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e40.00 [30 to 50]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e43.00 [32 to 60]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePost-extubation NRS scores\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2[1 to 3]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2[1 to 3]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2[1 to 3]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.00 [1 to 3]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e2.00 [1 to 3]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eType of surgery (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eThoracic surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e52 (34.21)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e256 (35.46)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e308 (35.24)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e47 (33.33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e94 (40.52)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLaparoscopic surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e70 (46.05)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e324 (44.88)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e394 (45.08)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e65 (46.10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e92 (39.66)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOpen abdominal surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8 (5.26)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e39 (5.40)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e47 (5.38)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e8 (5.67)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e9 (3.88)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHepatobiliary surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5 (3.29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33 (4.57)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e38 (4.35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e4 (2.84)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e14 (6.03)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.19\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNatural cavity surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 (1.97)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (2.49)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21 (2.40)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e3 (2.13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e5 (2.16)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHead \u0026amp; neck and breast cancer surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e12 (7.89)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43 (5.96)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e55 (6.29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e12 (8.51)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e13 (5.60)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrthopedic surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2 (1.32)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (0.69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7 (0.80)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2 (1.42)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e4 (1.72)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOther surgery\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (0.55)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4 (0.46)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0 (0.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1 (0.43)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCIA (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e133(87.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e635(87.95)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e768(87.87)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e125 (88.65)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e198 (85.34)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.104\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePACU rescue non-opioid analgesics (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e33(21.71)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e144(19.94)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e177(20.25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e26 (18.44)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e56 (24.14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.147\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePACU rescue opioid analgesics (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24 (15.79)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e17(2.35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e17 (2.35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e17 (12.06)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e16 (6.90)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.158\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of surgery (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e142[110 to 196.25]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e156 [120 to 215.75]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e155 [116 to 214]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e143 [110 to 197]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e156 [127 to 219.25]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.19\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e\u003cp\u003eNote: Data were presented as mean (SD), median [IQR], or n (%); RD: Respiratory depression; PACU: Post-anesthesia care unit; PSM: Propensity score matched; BMI: Body mass index; ASA: American Society of Anesthesiologists; SMD: Standard mean difference; CAD: Coronary artery disease; PCIA: patient-controlled intravenous analgesia; \u003csup\u003e*\u003c/sup\u003e Definition of other surgery was showed appendix (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Definition of variables)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eDuring the study period, 896 patients were enrolled in the prospective cohort. Of these, seven were transferred to the ICU postoperatively, eight experienced intraoperative hemorrhage exceeding 1500 ml, and seven had incomplete data. A total of 874 patients were therefore included in the final analysis. Figure\u0026nbsp;1 displays the participant selection process. In the PACU, 152 patients (17.4%) developed RD. The median age of the all patients was 55.79 years (standard deviation: 11.51), and 335 patients (38.33%) were male. In terms of ASA classification, 378 patients (43.25%) were ASA II and 495 patients (56.64%) were ASA III. The most frequent types of surgery were laparoscopic (394 patients, 45.08%) and thoracoscopic (308 patients, 35.24%). Baseline characteristics are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n\u003ch3\u003eRisk factors for the PACU\u003c/h3\u003e\n\u003cp\u003eMultivariate logistic regression identified the following independent risk factors for RD in the PACU: age (OR 1.02, 95% CI 1.0 to 1.04, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.034), ASA class III (OR 1.97, 95% CI 1.21 to 3.2, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.006), preoperative lung disease (OR 4.04, 95% CI 2.42 to 6.72, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), preoperative hypoxemia (OR 2.03, 95% CI 1.02 to 4.06, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.044), preoperative hypercapnia (OR 3.03, 95% CI 2.93 to 7.75, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.03), intraoperative hypothermia (OR 8.61, 95% CI 4.12 to 17.97, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and rescue opioid use in the PACU (OR 7.19, 95% CI 3.4 to 15.23, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). These associations are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. VIF analysis indicated no multicollinearity among the independent variables; detailed results are provided in the Appendix.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFactors associated with RD in PACU\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eUnivariable logistic regression\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e\u003cp\u003eMultivariable logistic regression\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOR (95% CI)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOR (95% CI)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.04 (1.02 to 1.06)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.02 (1.0 to 1.04)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.034\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.08 (1.03 to 1.14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.004\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.05(0.99 to 1.13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.135\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.91 (0.64 to 1.30)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.615\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSTOP-Bang scores\u0026thinsp;\u0026ge;\u0026thinsp;3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.63 (1.56 to 4.45)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.70 (0.92 to 3.16)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.091\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eASA classification\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIII\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.68 (1.80 to 3.97)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.97 (1.21 to 3.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.006\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eⅣ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.00 (0.00 to Inf)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.983\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSmoking\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.98 (0.56 to 1.71)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.951\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlcohol abuse\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.54 (0.84 to 2.82)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.166\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative hypertension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.27 (1.50 to 3.46)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.66 (0.98 to 2.73)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.078\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative CAD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.69 (0.70 to 4.08)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative diabetes mellitus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.05 (1.17 to 3.61)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.013\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.36 (0.70 to 2.64)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.363\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative stroke\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.69 (0.89 to 3.18)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.107\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.77 (0.37 to 1.62)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.494\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative lung diseases\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.37 (2.80 to 6.82)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.04 (2.42 to 6.72)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative hypoxemia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.46 (1.32 to 4.59)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.005\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.03 (1.02 to 4.06)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.044\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative hypercapnia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.84 (1.65 to 8.93)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.002\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.03 (2.93 to 7.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.03\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative hepatic insufficiency\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.33 (0.49 to 3.64)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.578\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative hypoproteinemia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.79 (0.23 to 2.70)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.703\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative renal insufficiency\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e19.49 (2.16 to 175.40)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.008\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8.04 (0.59 to 109.96)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.118\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnesthesia method\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.08 (0.94 to 4.64)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.072\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative hypothermia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.06 (2.67 to 9.59)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8.61 (4.12 to 17.97)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative hypotension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.26 (0.03 to 1.95)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.22 (0.03 to 1.83)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.162\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative dose of sufentanil\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.01 (0.99 to 1.03)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.606\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of last of sufentanil\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.00 (0.99 to 1.01)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.712\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of last of muscle relaxant\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.01 (1.00 to 1.02)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.186\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative fluids\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.00 (1.00 to 1.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.362\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative bleeding\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.00 (1.00 to 1.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.096\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.00 (1.00 to 1.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e0.124\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePost-extubation NRS scores\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.98 (0.87 to 1.10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.707\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCIA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.96 (0.56\u0026thinsp;~\u0026thinsp;1.63)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.877\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePACU rescue non-opioid analgesics\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.11 (0.73\u0026thinsp;~\u0026thinsp;1.71)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.623\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePACU rescue opioid analgesics\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.78 (4.06\u0026thinsp;~\u0026thinsp;14.88)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7.19 (3.40\u0026thinsp;~\u0026thinsp;15.23)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eType of surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.02 (0.91 to 1.15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.00 (1.00 to 1.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.917\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003eNote: RD: Respiratory depression; PACU: Post-anesthesia care unit; BMI: Body mass index; ASA: American Society of Anesthesiologists; PCIA: Patient-controlled intravenous analgesia; NRS: Numerical rating scale; OR: odds ratio; CI: Confidence interval\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c6\" namest=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003eEffects of RD in the PACU after PSM\u003c/h3\u003e\n\u003cp\u003eIn this cohort study, baseline characteristics were well balanced between the exposure groups after PSM was applied to adjust for relevant variables. A total of 141 patients experienced RD in the PACU, while 232 patients did not. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the baseline characteristics of the matched study population. Multivariate logistic regression analysis showed that RD in the PACU significantly increased the risk of PPCs (OR 3.26, 95% CI 1.03 to 10.27; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.044), postoperative pneumonia (OR 3.00, 95% CI 1.15 to 7.8; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.024), unplanned ICU transfer (OR 3.81, 95% CI 1.07 to 13.57; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.039), and longer average hospital stay (OR 1.04, 95% CI 1.01 to 1.09; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.033). The incidence of postoperative pneumothorax was low. Before PSM, three cases occurred in the RD group and five in the non-RD group. After PSM, no cases were recorded in the RD group, and one case remained in the non-RD group. No statistical analysis was performed for postoperative pneumothorax due to the small numbers. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the impact of PACU RD on postoperative outcomes. VIF analysis indicated no multicollinearity among independent variables, and the corresponding data are provided in the Appendix. Distributional balance plots for distance and covariates are also included in the Appendix.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eEffect of RD in PACU on PPCs\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOutcomes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eRD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eUnivariable logistic regression\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMultivariable logistic regression\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes(n\u0026thinsp;=\u0026thinsp;141)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNo(n\u0026thinsp;=\u0026thinsp;232)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOR (95%CI), \u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eOR (95%CI), \u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePPCs (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e66 (46.81)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e32 (13.79)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.50 (3.34 to 9.06), \u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.26 (1.03 to 10.27), \u003cb\u003e0.044\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePostoperative pneumonia (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e47 (33.33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15 (6.47)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7.23 (3.85 to 13.58), \u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.00 (1.15 to 7.80), \u003cb\u003e0.024\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePostoperative hypoxemia (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6 (4.26)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (1.29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.39 (0.83 to 13.79), 0.088\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.50 (0.30 to 7.56), 0.624\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePleural effusion (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30 (21.28)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23 (9.91)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.46 (1.36 to 4.43), \u003cb\u003e0.003\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.33 (0.11 to 1.02), 0.055\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAtelectasis (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e53 (37.59)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24 (10.34)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.22 (3.03 to 8.98), \u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.84 (0.69 to 4.90), 0.224\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUnplanned ICU admission (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 (7.09)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (1.72)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.35 (1.34 to 14.15), \u003cb\u003e0.015\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.81 (1.07 to 13.57), \u003cb\u003e0.039\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAverage hospital stays (days)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.00 [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.06 (1.02 to 1.1), \u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.04 (1.01 to 1.09), \u003cb\u003e0.033\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003eNotes: Data were presented as median [IQR], or n (%); RD: Respiratory depression; PACU: Post-anesthesia care unit; PPCs: Postoperative pulmonary complications; ICU: Intensive care unit; OR: odds ratio; CI: Confidence interval\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, the incidence of RD in the PACU was approximately 17.4%. Independent risk factors identified were age, ASA III classification, preoperative pulmonary disease, hypoxemia, hypercapnia, intraoperative hypothermia, and the use of rescue opioids in the PACU. RD in the PACU significantly increased the risk of PPCs, unplanned ICU transfer from the PACU, and extended hospital stay, but it did not affect the rates of postoperative hypoxemia, pleural effusion, or atelectasis by the time of discharge.\u003c/p\u003e\u003cp\u003eThe primary mechanisms contributing to RD in the PACU are insufficient ventilation and compromised gas exchange. Central respiratory depression caused by opioids and sedatives is the leading cause, followed by effects from mechanical ventilation and postoperative atelectasis, particularly in thoracic or upper abdominal procedures. These factors limit effective gas exchange. Chun et al. found that 78% of patients requiring intervention were identified through carbon dioxide monitoring in the PACU, while only 6% were detected through clinical assessment alone [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. RD is often episodic, with normal breathing intervals, and may resemble simple drowsiness [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Additionally, suboptimal allocation of PACU resources contributes to under recognition. As such, identifying patients at higher risk for RD remains essential. The PRODIGY trial listed several risk factors for postoperative RD, including age\u0026thinsp;\u0026gt;\u0026thinsp;60 years, sex, opioid naivety, sleep disorders, chronic heart failure, and sleep-disordered breathing [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, these findings primarily focused on the role of opioid use after surgery. Other studies have shown that factors such as low BMI, preoperative opioid or gabapentin use, high intraoperative doses of opioids or midazolam, and the use of isoflurane can increase the likelihood of RD following extubation in the PACU, particularly in patients undergoing total joint replacement or laparoscopic surgery [\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Upper abdominal and thoracic surgeries, which more directly affect respiratory function, are associated with higher rates of PPCs [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Ageing increases patient sensitivity to opioids and anesthetics, thereby raising the risk of RD. We found that preoperative lung disease was an independent risk factor for RD in the PACU. This may be related to worsened atelectasis and increased intrapulmonary shunting caused by underlying lung pathology, as well as renal impairment that delays drug clearance. Additionally, preoperative hypoxemia and hypercapnia were both significantly associated with elevated RD risk. Reduced overall health status and reduced cardiopulmonary reserve, reflected in older age and ASA class III, also contributed to RD occurrence in the PACU. These findings align with those reported by Khanna et al. [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Inadequate intraoperative pain control can result in severe post-extubation discomfort, prompting the need for additional opioid administration in the PACU, which further increases RD risk. Intraoperative hypothermia is commonly observed in surgical patients and can impair drug metabolism, trigger shivering, and delay PACU discharge [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. This study is the first, to our knowledge, to identify intraoperative hypothermia as an independent risk factor for RD in the PACU. The STOP-Bang questionnaire is widely used to assess preoperative risk for obstructive sleep apnea (OSA) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], but its value in predicting postoperative hypoxemia has been questioned [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Our findings support this, showing that a STOP-Bang score\u0026thinsp;\u0026ge;\u0026thinsp;3 was not an independent predictor of RD in the PACU.\u003c/p\u003e\u003cp\u003eAn association was observed between RD in the PACU and subsequent respiratory complications in the general care unit. Gali et al. reported that patients who developed RD in the PACU were more likely to experience postoperative respiratory issues [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Additionally, the use of naloxone in the PACU to reverse opioid-induced RD may significantly increase the risk of postoperative complications [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Our findings showed that RD in the PACU significantly increases the incidence of PPCs and pneumonia. Pulmonary atelectasis and pneumonia, both common postoperative outcomes linked to surgery, mechanical ventilation, and patient-initiated extubation, contribute to RD in the PACU and may continue to affect respiratory status beyond the PACU. Our study also demonstrated that RD in the PACU led to higher rates of unplanned ICU transfer and longer hospital stays. However, we did not observe an increased risk of other pulmonary complications. While the cohort included low-risk surgical patients with a low overall incidence of postoperative pleural effusion and hypoxaemia, some data were missing after PSM, which limits interpretation. These findings warrant further investigation in studies with larger sample sizes.\u003c/p\u003e\u003cp\u003eUnlike prior studies focused on postoperative opioid-induced RD, our study specifically evaluated low-risk surgical patients, who are often overlooked in PACU monitoring. In the PRODIGY trial, OSA and heart failure were identified as risk factors for opioid-induced RD [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In our study, however, the number of patients with a preoperative diagnosis of OSA (n\u0026thinsp;=\u0026thinsp;2) or heart failure (n\u0026thinsp;=\u0026thinsp;3) was too small to support statistical analysis. Neuromuscular blocking agents are another possible contributor to RD in the PACU. However, we found no significant association between their use and RD. All patients in our study underwent TOFr monitoring, received appropriate reversal agents, and were extubated only after the TOF ratio exceeded 0.9.\u003c/p\u003e\u003cp\u003eThe limitations of this study are as follows: although previous research has shown that RD in the PACU increases the risk of subsequent postoperative RD, we did not evaluate postoperative RD beyond the PACU due to constraints in personnel and monitoring equipment. Additionally, our study did not examine long-term postoperative mortality or complications such as cerebral infarction, cardiac events, or infections. As a single-centre study, the sample size was limited and may not be representative of broader populations.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOur findings indicate that age, ASA class III, preoperative pulmonary disease, hypoxemia, hypercapnia, intraoperative hypothermia, and the use of rescue opioids in the PACU are independent risk factors for RD. RD in the PACU significantly increases the incidence of PPCs, postoperative pneumonia, unplanned ICU transfer from the PACU, and prolongs hospital stay. Patients presenting with these risk factors should receive careful monitoring in the PACU to help prevent RD, lower the risk of complications, and improve overall outcomes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no acknowledgements to report.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDan Wang: Data curation, Visualization, Investigation, Writing-original draft; Kai Li: Data curation, Visualization, Writing-original draft; Shufang Sun: Data curation, Methodology, Formal analysis, Software; Qi Chen: Software, Validation, Writing-original draft; Qianyun Pang: Conceptualization, Methodology, Writing-review\u0026amp; editing; Ran An: Conceptualization, Methodology, Supervision, Writing-review\u0026amp; editing. All authors have read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the key research and development program of Chongqing Bureau of Science and Technology (cstc2020jscx-dxwtBX0010) and Chongqing Shapingba District Joint Medical Research Project of Science and Health (No.2024SQKWLHMS006) \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDe-identified data may be requested with reasonable justification from the authors (email to the corresponding author) and will be shared after approval, as per the authors\u0026rsquo; Institution\u0026rsquo;s policy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and informed consent\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthical approval for this study was granted by the Ethics Committee of the Chongqing University Cancer Hospital (CZLS2022109-A-44). All participants and their parents provided written informed consent, and this study was conducted in accordance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHolst JM, Klitholm MP, Henriksen J, Vallentin MF, Jessen MK, Bolther M, Holmberg MJ, H\u0026oslash;ybye M, Lind PC, Granfeldt A\u003cem\u003e et al\u003c/em\u003e: \u003cstrong\u003eIntraoperative respiratory and hemodynamic strategies for reducing nausea, vomiting, and pain after surgery: Systematic review and meta‐analysis\u003c/strong\u003e. \u003cem\u003eActa Anaesthesiologica Scandinavica \u003c/em\u003e2022, 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Review and Bayesian Meta-analysis of Prospective and Retrospective Cohort Studies\u003c/strong\u003e. \u003cem\u003eAnesthesia and analgesia \u003c/em\u003e2017, \u003cstrong\u003e125\u003c/strong\u003e(4):1301-1308.\u003c/li\u003e\n\u003cli\u003eKhanna AK, Sessler DI, Sun Z, Naylor AJ, You J, Hesler BD, Kurz A, Devereaux PJ, Saager L: \u003cstrong\u003eUsing the STOP-BANG questionnaire to predict hypoxaemia in patients recovering from noncardiac surgery: a prospective cohort analysis\u003c/strong\u003e. \u003cem\u003eBritish journal of anaesthesia \u003c/em\u003e2016, \u003cstrong\u003e116\u003c/strong\u003e(5):632-640.\u003c/li\u003e\n\u003cli\u003eGali B, Whalen FX, Schroeder DR, Gay PC, Plevak DJ: \u003cstrong\u003eIdentification of patients at risk for postoperative respiratory complications using a preoperative obstructive sleep apnea screening tool and postanesthesia care assessment\u003c/strong\u003e. \u003cem\u003eAnesthesiology \u003c/em\u003e2009, \u003cstrong\u003e110\u003c/strong\u003e(4):869-877.\u003c/li\u003e\n\u003cli\u003eDeljou A, Hedrick SJ, Portner ER, Schroeder DR, Hooten WM, Sprung J, Weingarten TN: \u003cstrong\u003ePattern of perioperative gabapentinoid use and risk for postoperative naloxone administration\u003c/strong\u003e. \u003cem\u003eBritish journal of anaesthesia \u003c/em\u003e2018, \u003cstrong\u003e120\u003c/strong\u003e(4):798-806.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Respiratory depression, Risk factors, Postoperative pulmonary complications","lastPublishedDoi":"10.21203/rs.3.rs-6948468/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6948468/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eRespiratory depression (RD) is a frequent postoperative complication in the post-anesthesia care unit (PACU). This prospective cohort study investigated the risk factors for RD and examined its impact on postoperative pulmonary complications (PPCs).\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eData were collected from June 2022 to August 2023 at a tertiary care Centre. Patients were assigned to RD or non-RD groups based on the occurrence of RD in the PACU, defined as SpO₂ \u0026lt; 90%, respiratory rate\u0026thinsp;\u0026lt;\u0026thinsp;8/min, apnea\u0026thinsp;\u0026ge;\u0026thinsp;10 s, or analgesia-sedation mismatch. The primary objective was to identify risk factors for RD in the PACU. Secondary outcomes included the incidence of RD and its effect on PPCs.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eRD was observed in 152 patients (17.4%). Multivariate logistic regression analysis revealed that age (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.034), American Society of Anesthesiologists (ASA) III classification (P\u0026thinsp;=\u0026thinsp;0.006), preoperative lung disease (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), preoperative hypoxemia (P\u0026thinsp;=\u0026thinsp;0.044), preoperative hypercapnia (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.03), intraoperative hypothermia (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and PACU rescue opioid analgesics (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) were independent risk factors for RD in the PACU. RD in the PACU was significantly associated with an increased incidence of PPCs (OR\u0026thinsp;=\u0026thinsp;3.81, 95%CI 1.07 to 13.57, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.044), postoperative pneumonia (OR\u0026thinsp;=\u0026thinsp;3.00, 95%CI 1.15 to 7.8, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.024), unplanned transfer to ICU (OR\u0026thinsp;=\u0026thinsp;3.81, 95%CI 1.07 to 13.57, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.039) and prolonged hospital stay (OR\u0026thinsp;=\u0026thinsp;1.04, 95%CI 1.01 to 1.09, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.033).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eAge, ASA III classification, pre-existing pulmonary disease, hypoxemia, hypercapnia, intraoperative hypothermia, and rescue opioid use in the PACU are independent risk factors for RD. RD in the PACU is associated with increased risk of PPCs and other adverse postoperative outcomes.\u003c/p\u003e\u003ch2\u003eTrial registry:\u003c/h2\u003e\u003cp\u003eChinese Clinical Trial Registry ChiCTR2200061256. Registered on 18 June, 2022.\u003c/p\u003e","manuscriptTitle":"Risk factors for respiratory depression and its effect on postoperative pulmonary complications in the PACU: A prospective cohort study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-18 14:11:12","doi":"10.21203/rs.3.rs-6948468/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"17457d93-bf2c-4787-bb28-d608ecc35667","owner":[],"postedDate":"July 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-18T14:11:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-18 14:11:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6948468","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6948468","identity":"rs-6948468","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}