Association Between Intra-Abdominal Pressure and Post-Spinal Hypotension During Cesarean Delivery: A Prospective Observational Study

Association Between Intra-Abdominal Pressure and Post-Spinal Hypotension During Cesarean Delivery: A Prospective Observational 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 Association Between Intra-Abdominal Pressure and Post-Spinal Hypotension During Cesarean Delivery: A Prospective Observational Study Rui Ma, Tao Xu, Shanshan Ye, Liqiang Zheng, Jing Zheng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6644561/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 Post-spinal hypotension can be exacerbated by increased pressure on the inferior vena cava during cesarean delivery. We examined the relationship between intra-abdominal pressure and post-spinal hypotension. Methods This prospective study included 83 parturients, aged 20–40 years, who underwent elective cesarean delivery in a tertiary level A maternity and child health hospital. Intra-abdominal pressure was measured before the induction of spinal analgesia. A receiver operating characteristic curve was used to determine the optimum cutoff value of intra-abdominal pressure for post-spinal hypotension. Univariable and multivariable logistic regression analyses were performed to explore the association between intra-abdominal pressure or binary classification based on the optimal intra-abdominal pressure cutoff value and hypotension after spinal anesthesia. Results A linear correlation was observed between the decrease in systolic arterial pressure from baseline and intra-abdominal pressure (r = 0.455; P < 0.001). The area under the receiver operating characteristic curve for predicting post-spinal hypotension was 0.92 (95% confidence interval: 0.85–0.99), with an optimal cutoff of 12.5 mm Hg. Intra-abdominal pressure was revealed as an independent risk factor for post-spinal hypotension in the logistic regression analysis. Parturients with an intra-abdominal pressure of ≥ 12.5 mm Hg had 93.73 times the odds of developing post-spinal hypotension than those with an intra-abdominal pressure < 12.5 mm Hg. The occurrence (92.7% vs. 11.9%, P < 0.001) of post-spinal hypotension was different between the two intra-abdominal pressure groups. Conclusions Intra-abdominal pressure was an independent risk factor for post-spinal hypotension during cesarean delivery. A cutoff value of ≥ 12.5 mm Hg could predict subsequent hypotension, while higher intra-abdominal pressure may be associated with a higher incidence of and more severe hypotension before delivery. intra-abdominal hypertension cesarean delivery spinal anesthesia hypotension Figures Figure 1 Figure 2 Figure 3 Figure 4 BACKGROUND Hypotension after the induction of spinal anesthesia during cesarean delivery occurs in 50 − 70% of parturients 1 . This complication is mainly caused by a rapid decline in peripheral circulation resistance due to sympathetic nervous system block and increased uterine pressure on the inferior vena cava (IVC), which exacerbates post-spinal hypotension 2 . Consequently, adverse effects—including nausea, vomiting, dyspnea, and fetal distress—can occur in both the mother and fetus. Therefore, effective prediction of post-spinal hypotension is essential for ensuring maternal and neonatal safety and increasing maternal comfort. Intra-abdominal pressure (IAP) is defined as the steady state of pressure within the abdominal cavity 3 . IAP increases significantly with the growing fetus and amniotic fluid during pregnancy 4 . Several studies 5 , 6 have validated that increased IAP could aggravate the pressure on the IVC via direct compression. The size of the uterus or diameter of the compressed IVC cannot be easily measured during the third trimester, while IAP could be measured using a transurethral catheter before cesarean delivery. Thus, we hypothesized that baseline IAP could be associated with post-spinal hypotension caused by the compression of the IVC. Hence, in the current study, we aimed to identify the relationship between IAP and post-spinal hypotension as well as determine the cutoff value of IAP and its potential to predict hypotension after the induction of spinal anesthesia during cesarean delivery. These findings will enable personalized strategies for parturients before anesthesia. METHODS This prospective observational study was approved by the Medical Research Ethics Committee of the International Peace Maternity and Child Health Hospital, Shanghai, China (Chairperson Zhiwei Liu) on September 19, 2023 (GKLW-A-2023-035-01). The study was designed in accordance with the applicable STROBE guidelines. Written informed consent was obtained from all the participants after recruitment. Inclusion and exclusion criteria Eighty-six full-term parturients with singleton pregnancies, aged 20–40 years, with heights ranging from 156 to 170 cm and an American Society of Anesthesiologists physical status classification of II, and who underwent elective cesarean delivery with combined spinal-epidural (CSE) anesthesia in the International Peace Maternity and Child Health Hospital were recruited between November 22, 2023 and February 26, 2024. The exclusion criteria were as follows: contraindications to spinal anesthesia, allergy to ropivacaine, preeclampsia or hypertension, underlying valvular disease detected by preoperative echocardiography, multiple pregnancies, body mass index [BMI] of > 35 kg/m 2 , active labor, emergency cesarean delivery, and parturient refusal. Parturients with difficult epidural puncture and an anesthesia level below T6 before surgery were also withdrawn after enrolment. Study design All parturients fasted overnight and were administered 500 mL crystalloid solution through an 18 G cannula within half an hour after entering the operating room. Routine monitoring included non-invasive blood pressure measurements, electrocardiography, and pulse oximetry, which was performed continuously. Consecutive systolic arterial pressure (SAP) and heart rate (HR) values were recorded in the supine position every minute; the average of the first two readings was treated as the baseline. Parturients with an SAP of > 140 mm Hg were excluded for suspected hypertension. Measurement of IAP As routine practice, a transurethral 16 Fr Foley catheter was inserted to drain the bladder before anesthesia. Pressure measurements were recorded in the supine position using the intravesical pressure measurement system, according to the method described in the World Society of the Abdominal Compartment Syndrome (WSACS) guidelines 7 . The pressure measurement kit (Exadyn Combitrans Monitoring Set; B. Braun Melsungen AG, Germany) connected to a monitor (IntelliVue MP50; Philips Medical Systems Boeblingen GmbH, Germany) was used to determine the IAP value. The mid-axillary level in the supine position and a 25 mL bladder inflation volume were considered the zero reference. The first steady value was considered the IAP value. IAP and other maternal characteristics were measured and recorded by a trained researcher; the anesthesiologist and the parturients were blinded to these measurements. Procedure for anesthesia induction An anesthesiologist with over 15 years of experience routinely performed the CSE puncture at the L3–4 interspace with the parturient in the right lateral position. A 17 G Tuohy needle was used, followed by the insertion of a 27 G Whitacre needle through the Tuohy needle to access the subarachnoid space. Upon identification of cerebrospinal fluid, 15 mg 0.5% plain ropivacaine was injected. An epidural catheter was then inserted 4 cm into the epidural space. Subsequently, the parturient was moved to the supine position, and a 30-degree wedge was placed under the right hip. The upper anesthesia level was assessed by pinprick; parturients whose anesthesia level remained below T6 at the beginning of surgery were withdrawn from the study. SAP and HR were recorded every minute for 12 min before delivery and then every 5 min until the end of surgery. Hypotension was defined as a drop in SAP of > 20% from the baseline value. A rescue dose of 50 µg phenylephrine was administered upon the occurrence of hypotension. Bradycardia, defined as an HR of < 50 beats/min, was treated using intravenous atropine (0.5 mg). After delivery, Apgar scores at 1 and 5 min, along with neonatal body weights, were recorded. An obstetrician immediately collected 1 mL umbilical artery (UA) blood, and blood gas assessments were performed using a blood gas analyzer (Edan i15 Blood Gas Analyzer; ICEN, Guangdong, China) with an iSTAT BG10 test cartridge. The primary outcome was the association between IAP and post-spinal hypotension during cesarean section. Maternal and obstetric characteristics included age, height, weight, BMI, gravidity, parity, amniotic fluid index, expected fetal weight by ultrasound within 1 week before cesarean section, uterine height, abdominal circumference, total doses of phenylephrine and atropine administered, upper anesthesia level, incision–delivery interval, neonatal body weight, Apgar scores at 1 min and 5 min, pH and base excess of UA blood, and maternal adverse symptoms. Sample size calculation and statistical analysis Based on clinical experience, the probability of hypotension occurring during cesarean delivery after administering 15 mg 0.5% plain ropivacaine into the subarachnoid space is approximately 50% 8 . Assuming equal numbers of parturients with and without hypotension and using IAP as an indicator, with α = 0.05, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve for IAP was 0.8 with a confidence interval (CI) width of 0.2. The sample size calculated using Power Analysis and Sample Size 2021 was 78. Considering a dropout rate of 10%, this study required at least 86 parturients. The Tidyverse package was used for data cleaning, Table One package for summarizing baseline characteristics, car package for exploring collinearity issues, pROC package for generating ROC curves, base R package for fitting logistic regression models, and ggplot2 package for creating additional plots. All analyses were conducted using R 4.4.1 (R Foundation for Statistical Computing, Vienna, Austria). Significance was defined as a P -value of < 0.05. The Kolmogorov–Smirnov test was used for determining whether variables were normally distributed. Maternal and obstetric characteristic data are presented as means ± standard deviations for normally distributed continuous variables, medians (P25, P75) for skewed continuous variables, and percentages for categorical variables. A scatterplot was constructed to assess the linearity between IAP and the decrease in SAP, and a linear correlation was plotted. Spearman’s rank correlation was used to assess the correlations between IAP measured before anesthesia and the decrease in SAP from baseline. An ROC curve was then constructed to assess suitable diagnostic thresholds based on the Youden index, balancing specificity and sensitivity. Two steps of logistic regression were used in this study. Both univariate and multivariable logistic regressions were used in step 1 to evaluate the predictive value of IAP for hypotension after anesthesia. The following factors were first included in the univariate regressions: IAP, age, BMI, gravidity, gestational week, expected weight of baby by ultrasound, uterine height, and abdominal circumference that may relate to post-spinal hypotension; the odds ratios (ORs) and their 95% CIs for hypotension were determined with IAP as a continuous variable (1 mm Hg). Subsequently, the variables that were univariably associated ( P < 0.05) with hypotension, along with clinically relevant variables, were included in the multivariable model building; ORs with 95% CIs were also reported. The degree of multicollinearity using the variance inflation factor (VIF) was assessed, and variables with a VIF of > 10 were dropped. In step 2, only univariate logistic regression was performed to evaluate the ORs and their CIs, with the IAP categorized into two groups (< 12.5 mm Hg and ≥ 12.5 mm Hg, using the best threshold from the ROC curve based on the Youden index). Comparisons between parturients with normal and high IAP (IAP < 12.5 mm Hg or ≥ 12.5 mm Hg) were performed using the Student t -test, Mann–Whitney U test, and χ 2 test. Differences in SAP and HR for a successive 12 min after the induction of spinal anesthesia between the groups with normal and high IAP were assessed using two-way analysis of variance and the Bonferroni post-hoc test. RESULTS Patient characteristics A total of 122 parturients were recruited, of whom 86 met the inclusion criteria and participated in the current study. Eighteen parturients underwent emergency cesarean sections, nine had preeclampsia, five had multiple pregnancies, one had morbid obesity (BMI ≥ 36 kg/m 2 ), and three refused to participate, resulting in their exclusion from the study. Additionally, the data of three parturients were excluded from further analysis because of inadequate blockade of anesthesia. The analysis was based on the remaining 83 data sets (Fig. 1 ). The maternal and obstetric characteristics of all the parturients, and categorized into hypotension (n = 42) and non-hypotension (n = 40) groups, are presented in Table 1 . The mean IAP before anesthesia induction was higher in the hypotension than in the non-hypotension group (14.9 ± 2.3 mm Hg vs. 10.5 ± 2.3 mm Hg, P < 0.001). The distribution of measured IAP showed differences between the two groups. Other characteristics that also significantly differed between the groups included height, BMI, expected fetal weight by ultrasound, uterine height, and abdominal circumference. Table 1 Maternal and obstetric characteristics of all parturients and categorized into hypotension and non-hypotension groups Variables Total (N = 83) Non-hypotension (N = 40) Hypotension (N = 43) P value Age (yr) 32.7 ± 3.7 33.7 ± 3.5 31.7 ± 3.7 0.012 Height (cm) 162.2 ± 3.6 163.4 ± 3.0 161.2 ± 3.9 0.005 Weight (kg) 70.5 ± 9.3 68.7 ± 9.0 72.2 ± 9.4 0.090 BMI (kg/m 2 ) 26.8 ± 3.3 25.7 ± 3.0 27.8 ± 3.3 0.004 Gestational week (wk) 38.64 ± 0.96 38.51 ± 0.99 38.77 ± 0.92 0.232 Gravidity 2 (1, 3) 1 (1, 2) 2 (1, 3) 0.050 Parity 0 (0, 1) 0 (0, 1) 0 (0, 1) 0.570 AFI (mm) 129.2 ± 32.2 127.1 ± 33.0 131.1 ± 31.8 0.574 Expected foetal weight (g) 3274.0 ± 440.9 3140.6 ± 421.9 3398.1 ± 426.1 0.007 Uterine height (cm) 36.9 ± 3.8 35.7 ± 3.6 38.0 ± 3.8 0.005 Abdominal circumference (cm) 96.2 ± 7.2 93.9 ± 6.7 98.5 ± 7.0 0.003 IAP (mmHg) 12.8 ± 3.2 10.5 ± 2.3 14.9 ± 2.3 < 0.001 IAP, n (%) < 0.001 15 mmHg 19 (22.9) 2 (5) 17 (39.5) Values are mean ± SD or median (IQR) IQR: interquartile range; SD = standard deviation;BMI: body mass index; AFI: Amniotic Fluid Index; IAP: Intra-abdominal Pressure. Correlation between IAP and decrease in SAP A linear correlation was observed between IAP and the decrease in SAP from baseline ( r = 0.455; P < 0.001; Fig. 2 ). ROC analysis and cutoff value for IAP The ROC analysis revealed that IAP effectively detected parturients at risk of hypotension, with an AUC of 0.92 (95% CI: 0.85 to 0.99, P < 0.001; Fig. 3 ). The optimal IAP cutoff was 12.5 mm Hg, yielding a sensitivity of 92%, specificity of 88%, positive predictive value of 93%, and negative predictive value of 88% (Fig. 3 ). Logistic regression analysis of IAP and risk of post-spinal hypotension Both univariate and multivariable logistic regression were used in step 1. Parturients with a higher IAP, BMI, expected weight of the baby by ultrasound, uterine height, and abdominal circumference were at risk of developing hypotension after the induction of spinal anesthesia, while advanced age emerged as a protective factor against developing hypotension through univariate logistic regression. In the multivariable model, IAP was found to be an independent risk factor after adjusting for the variables identified in the univariate logistic regression. For every 1 mm Hg increase in IAP, parturients had 2.24 times the odds of developing post-spinal hypotension (95% CI: 1.6 to 3.6, P < 0.001) (Table 2 ). Table 2 Univariable and multivariable analysis of risk factors associated with hypotension Variable Univariate Multivariate OR (95% CI) p- value OR (95% CI) p- value Step 1 IAP 2.26 (1.68–3.35) < 0.001 2.24 (1.6–3.6) < 0.001 Age 0.85 (0.74–0.97) 0.016 0.85 (0.67–1.04) 0.152 BMI 1.23 (1.07–1.44) 0.007 1.14 (0.79–1.69) 0.504 gravidity 1.36 (0.96–2.01) 0.093 1.7 (1.02–3.08) 0.055 Gestational week 1.54 (0.97–2.52) 0.076 0.99 (0.38–2.55) 0.986 Expect weight 1.16 (1.04–1.3) 0.01 1.18 (0.92–1.55) 0.204 Uterine height 1.19 (1.05–1.36) 0.008 1.09 (0.88–1.36) 0.452 Abdominal circumference 1.11 (1.03–1.19) 0.005 0.95 (0.78–1.14) 0.601 Step 2 IAP < 12.5 mmHg 1 (ref) N/A N/A IAP ≥ 12.5 mmHg 93.73 (24.02–511.66) < 0.001 BMI: body mass index; IAP: Intra-abdominal Pressure. In step 2, univariate logistic regression was used to evaluate the ORs and their CIs, with IAP categorized into normal and high groups (< 12.5 mm Hg and ≥ 12.5 mm Hg). Parturients with a high IAP had 93.73 times the odds of developing post-spinal hypotension than did those with a normal IAP (95% CI: 24.02 to 511.66, P < 0.001) (Table 2 ). Hemodynamic changes after spinal analgesia induction based on IAP Parturients with both a high and normal IAP experienced a decrease in SAP after the induction of spinal analgesia. Parturients with an IAP of ≥ 12.5 mm Hg exhibited a lower SAP than did those with an IAP of < 12.5 mm Hg at 1, 2, 3, 4, 5, 6, 10, 11, and 12 min after spinal anesthesia induction. HRs were not significantly different between the two IAP groups after the induction of spinal anesthesia (Fig. 4 ). Clinical outcomes Parturients with an IAP of ≥ 12.5 mm Hg with a greater occurrence (92.7% vs. 11.9%, P < 0.001) of post-spinal hypotension required higher doses of phenylephrine (0 [0, 0] vs. 100 [50, 100] µg, P < 0.001) or longer rescue times with phenylephrine (0 [0, 0] vs. 1 [1, 2], P = 0.005) before delivery. The incidence of nausea was also higher in parturients with an IAP of ≥ 12.5 mm Hg (0% vs. 17.1%, P = 0.005). Parturients with an IAP of ≥ 12.5 mm Hg exhibited a greater fetal birth weight (3513.7 ± 480.8 vs. 3221.8 ± 493.7 g, P = 0.008) than did those with an IAP of < 12.5 mm Hg. The results of the UA blood analysis and Apgar scores at 1 and 5 min did not differ between the two groups (Table 3 ). Table 3 Maternal and neonatal observations between normal IAP (IAP < 12.5mmHg) and high IAP (IAP ≥ 12.5mmHg) groups Variables Normal IAP (n = 42) High IAP (n = 41) P value Post-spinal hypotension, n (%) 5 (11.9) 38 (92.7) < 0.001 Phenylephrine dose (µg) 0 (0, 0) 100 (50,100) < 0.001 Phenylephrine times 0 (0, 0) 1 (1, 2) 0.005 Dyspnoea, n (%) 0 (0.0) 4 (9.8) 0.055 Nausea, n (%) 0 (0.0) 7 (17.1) 0.005 Induction-delivery interval (min) 9.7 ± 1.4 10.0 ± 2.0 0.450 The upper sensory level 4 (4, 4) 4 (4, 4) 0.337 Baby birth weight (g) 3221.8 ± 493.7 3513.7 ± 480.8 0.008 Apgar scores at 1 minute 10 (10, 10) 10 (10, 10) 0.494 Apgar scores at 5 minutes 10 (10, 10) 10 (10, 10) N/A pH 7.34 ± 0.05 7.33 ± 0.03 0.342 BE (mmol/L) -2.68 ± 1.48 -2.86 ± 1.74 0.681 Values are mean ± SD, number (percentage), or median (IQR). IQR: interquartile range; SD: standard deviation; BE: base excess. DISCUSSION In this study, IAP before spinal anesthesia induction was measured to determine the potential association between IAP and post-spinal hypotension. We observed that IAP was associated with the occurrence of hypotension after the induction of spinal anesthesia, and a cutoff value of ≥ 12.5 mm Hg could predict subsequent hypotension. Further, an increased IAP may be associated with a higher incidence and severity of hypotension before delivery. Post-spinal hypotension primarily occurs in two ways: blockade of the sympathetic nervous system after spinal anesthesia induction, which reduces peripheral vascular resistance, and compression of the uterus on the IVC after abdominal muscle relaxation 9 , 10 . Both these mechanisms are involved in reducing the amount of blood that returns to the heart. Previous methods for predicting the occurrence of hypotension after spinal anesthesia induction were primarily based on the assessment of maternal autonomic nervous system function before anesthesia induction 11 – 14 . However, an ideal prediction is difficult to achieve, as the assessment of autonomic nervous system function is influenced by many factors, such as maternal body movement, body temperature, and anxiety. Therefore, these methods are rarely used in clinical practice. The mechanism by which IAP predicts hypotension after spinal anesthesia induction may involve its reflection of uterine compression on the IVC, as previously mentioned. The authors of several studies outside the field of obstetric anesthesia have confirmed that IAP induces hypotension through IVC compression. Two studies have revealed that a prolonged increase in IAP may reduce cardiac output owing to direct compression of the IVC and portal vein 15 , 16 . Stacey et al. 5 and Hirabayashi et al. 6 validated that an increased IAP could aggravate the pressure on the IVC via direct compression. An animal experiment 17 further revealed that a higher IAP (> 15–20 mm Hg) may be associated with a lower additional gain in volume expansion but more hemodynamic side effects in rabbits. Although current research on the correlation between IAP and maternal hypotension after spinal anesthesia induction remains limited, observations in pregnant women in the third trimester provide indirect evidence that supine positioning often triggers hypotension and fetal distress 18 , 19 . This finding suggests that pregnancy-related IAP elevation intensifies IVC compression. Since sympathetic blockade is absent in this scenario, IVC compression stands as the sole plausible explanation for third-trimester hypotension. Notably, pregnancy inherently constitutes a state of progressive IAP increase 4 , 20 , 21 , making this physiological mechanism particularly relevant in obstetric anesthesia. Therefore, we have reason to believe that the higher the baseline IAP, the more pronounced the compression of the IVC, which further exacerbates maternal hypotension after spinal anesthesia induction. In our study, we also found that as IAP increased, the risk of hypotension significantly rose, and the magnitude of the drop in blood pressure was more substantial. These findings corroborate our above hypothesis regarding the mechanism of hypotension occurrence after spinal anesthesia induction during cesarean section. Despite the widespread use of prophylactic vasopressor agents 22 , 23 , predicting the risk of hypotension after the induction of spinal anesthesia seems less important. However, we believe that owing to the high predictive value of IAP before anesthesia induction for identifying hypotension, measuring IAP before anesthesia induction can not only help to reduce the prophylactic use of vasopressors in low-risk parturients but also, when encountering high-risk parturients with a significantly elevated IAP, facilitate the provision of a more comprehensive anesthesia plan. This may include more detailed pre-anesthesia education on adverse reactions related to hypotension, changing the anesthesia induction method (using epidural anesthesia or commencing with a lower spinal dose of local anesthetics with CSE), further shortening the time interval from anesthetic administration to fetal delivery 24 , 25 in high-risk parturients, or reducing or discontinuing the minute dosage of prophylactic vasopressors in low-risk parturients. These measures can offer a relatively comfortable anesthesia experience for parturients. Our study has several strengths. First, clinical consistency―the study results demonstrate only minor discrepancies when compared to the intra-abdominal hypertension diagnostic criteria established by the WSACS 5 . This confirms the dual clinical value of IAP as a predictive marker for hypotension following spinal anesthesia induction; it not only forecasts the risk of hypotension but also exhibits a significant correlation with the magnitude of blood pressure decline. Second, operational feasibility—in obstetric practice, urinary catheterization is routinely performed preoperatively for parturients undergoing cesarean sections. Consequently, IAP monitoring requires no additional invasive procedures, significantly lowering the technical implementation barrier. Finally, device versatility—existing arterial pressure monitoring kits are sufficient for IAP measurement, eliminating the need for specialized equipment. With the widespread adoption of this technique, the development of intelligent urinary catheters integrated with pressure-monitoring capabilities is anticipated, thereby optimizing clinical workflows. However, our study also has some limitations. First, the WSACS guidelines recommend the supine position for IAP measurements, with no specific reference to parturients. Therefore, the supine position was also used in this study. However, the parturient was moved to the supine position with a wedge placed under the right hip after anesthesia induction. IAP values might change with different positions. It is assumed that for a parturient in the lateral decubitus position, if the IAP exceeds the normal level when lying supine, the vertical pressure exerted on the IVC and abdominal aorta would also be elevated when the parturient lies on their side at the same angle. Second, we imposed some limitations on the height and weight of the enrolled parturients, which limits the generalizability of our results to specific populations while reducing selection bias. CONCLUSIONS Our findings confirms that IAP is an independent risk factor for post-spinal hypotension during cesarean delivery. A cutoff value ≥ 12.5 mm Hg could predict subsequent hypotension, and a higher IAP may be associated with a higher incidence and severity of hypotension before delivery. Further studies and more convenient IAP measurement methods are needed to explore its clinical feasibility. Abbreviations AUC area under the curve BMI body mass index CI confidence interval CSE combined spinal and epidural HR heart rate IAP intra-abdominal pressure IVC inferior vena cava OR odds ratio ROC receiver operating characteristic SAP systolic arterial pressure UA umbilical artery VIF variance inflation factor WSACS World Society of the Abdominal Compartment Syndrome Declarations Ethical approval and consent to participate This study was approved by the Medical Research Ethics Committee of the International Peace Maternity and Child Health Hospital, Shanghai, China (Chairperson Zhiwei Liu) on September 19, 2023 (GKLW-A-2023-035-01). Written informed consent was obtained from all the participants after recruitment. Consent for publication Not applicable. Availability of data and materials The data that underlie the results reported in this article and study protocol and the statistical analysis plan can be shared within 3 years following article publication with sound proposal. Proposals should be directed to [email protected] . Competing interests The authors declare that they have no competing interests. Funding Support was provided by the Fund of the International Peace Maternity and Child Health Hospital, Shanghai, China (A 3-year Action Plan for Clinical Research Program, IPMCH2022CR-07). Authors’ contributions RM helped with the data acquisition, analysis, and interpretation; writing of the first draft; and approval of the final version of the manuscript. TX helped with data acquisition, writing of the first draft, and approval of the final version of the manuscript. SY helped with the data analysis and interpretation and approval of the final version of the manuscript. LZ helped with the data analysis and interpretation and approval of the final version of the manuscript. JZ helped with the study conception and design, data analysis and interpretation, revision of the manuscript for important intellectual content, and approval of the final version of the manuscript. Acknowledgments We thank all the staff of the Clinical Research Center, the International Peace Maternity and Child Health Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China, for their efforts and support in the study. The study was pre-registered at http://www.chictr.org.cn on October 24, 2023 (ChiCTR2300076915), by Rui Ma, and the first patient was recruited on November 22, 2023. References Fitzgerald JP, Fedoruk KA, Jadin SM, Carvalho B, Halpern SH. Prevention of hypotension after spinal anaesthesia for caesarean section: a systematic review and network meta-analysis of randomised controlled trials. Anaesthesia. 2020;75:109-21. Salama ER, Elkashlan M. Pre-operative ultrasonographic evaluation of inferior vena cava collapsibility index and caval aorta index as new predictors for hypotension after induction of spinal anaesthesia: a prospective observational study. Eur J Anaesthesiol. 2019;36:297-302. Olerud S. Experimental studies on portal circulation at increased intra-abdominal pressure. Acta Physiol Scand Suppl. 1953;30:1-95. Jayasundara S, Goonewardene M, Dassanayake L. The association between maternal intra-abdominal pressure and hypertension in pregnancy. PLoS One. 2023;18:e0284230. Stacey T, Thompson JM, Mitchell EA, Ekeroma AJ, Zuccollo JM, McCowan LM. Association between maternal sleep practices and risk of late stillbirth: a case-control study. BMJ. 2011;342:d3403. Hirabayashi Y, Shimizu R, Fukuda H, Saitoh K, Igarashi T. Effects of the pregnant uterus on the extradural venous plexus in the supine and lateral positions, as determined by magnetic resonance imaging. Br J Anaesth. 1997;78:317-9. Kirkpatrick AW, Roberts DJ, De Waele J, Jaeschke R, Malbrain ML, De Keulenaer B, et al. Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome. Intensive Care Med. 2013;39:1190-206. Xu Z, Xu T, Zhao P, Ma R, Zhang M, Zheng J. Differential roles of the right and left toe perfusion index in predicting the incidence of postspinal hypotension during cesarean delivery. Anesth Analg. 2017;125:1560-6. Kundra P, Khanna S, Habeebullah S, Ravishankar M. Manual displacement of the uterus during Caesarean section. Anaesthesia. 2007;62:460-5. Lal J, Jain M, Rahul, Singh AK, Bansal T, Vashisth S. Efficacy of inferior vena cava collapsibility index and caval aorta index in predicting the incidence of hypotension after spinal anaesthesia- a prospective, blinded, observational study. Indian J Anaesth. 2023;67:523-9. Ouzounian JG, Masaki DI, Abboud TK, Greenspoon JS. Systemic vascular resistance index determined by thoracic electrical bioimpedance predicts the risk for maternal hypotension during regional anesthesia for cesarean delivery. Am J Obstet Gynecol. 1996;174:1019-25. Boyle SL, Moodley A, Al Azazi E, Dinsmore M, Massicotte EM, Venkatraghavan L. Preoperative heart rate variability predicts postinduction hypotension in patients with cervical myelopathy: a prospective observational study. Neurol India. 2022;70:S269-75. Bolea J, Lázaro J, Gil E, Rovira E, Remartínez JM, Laguna P, et al. Pulse rate and transit time analysis to predict hypotension events after spinal anesthesia during programmed cesarean labor. Ann Biomed Eng. 2017;45:2253-63. Toyama S, Kakumoto M, Morioka M, Matsuoka K, Omatsu H, Tagaito Y, et al. Perfusion index derived from a pulse oximeter can predict the incidence of hypotension during spinal anaesthesia for Caesarean delivery. Br J Anaesth. 2013;111:235-41. Rossi A, Cornette J, Johnson MR, Karamermer Y, Springeling T, Opic P, et al. Quantitative cardiovascular magnetic resonance in pregnant women: cross-sectional analysis of physiological parameters throughout pregnancy and the impact of the supine position. J Cardiovasc Magn Reson. 2011;13:31. Antoniou EA, Kairi E, Margonis GA, Andreatos N, Sasaki K, Damaskos C, et al. Effect of increased intra-abdominal pressure on liver histology and hemodynamics: an experimental study. In Vivo. 2018;32:85-91. Sümpelmann R, Schuerholz T, Marx G, Jesch NK, Osthaus WA, Ure BM. Hemodynamic changes during acute elevation of intra-abdominal pressure in rabbits. Paediatr Anaesth. 2006;16:1262-7. Saini BS, Ducas R, Darby JRT, Marini D, Sun L, Macgowan CK, et al. Feasibility of MRI assessment of maternal-fetal oxygen transport and consumption relative to maternal position in healthy late gestational pregnancies. J Physiol. 2023;601:5413-36. Jani D, Clark A, Couper S, Thompson JMD, David AL, Melbourne A, et al. The effect of maternal position on placental blood flow and fetoplacental oxygenation in late gestation fetal growth restriction: a magnetic resonance imaging study. J Physiol. 2023;601:5391-411. Arora V, Tyagi A, Ramanujam M, Luthra A. Intraabdominal pressure in non-laboring preeclamptic vs normotensive patients undergoing cesarean section: a prospective observational study. Acta Obstet Gynecol Scand. 2020;99:1031-8. Ozkan Seyhan T, Orhan-Sungur M, Basaran B, Savran Karadeniz M, Demircan F, Xu Z, et al. The effect of intra-abdominal pressure on sensory block level of single-shot spinal anesthesia for cesarean section: an observational study. Int J Obstet Anesth. 2015;24:35-40. Belin O, Casteres C, Alouini S, Le Pape M, Dupont A, Boulain T. Manually controlled, continuous infusion of phenylephrine or norepinephrine for maintenance of blood pressure and cardiac output during spinal anesthesia for cesarean delivery: a double-blinded randomized study. Anesth Analg. 2023;136:540-50. Khatoon F, Kocarev M, Fernando R, Naz A, Khalid F, Ibrahim Abdalla EO, et al. Optimal infusion rate of norepinephrine for prevention of spinal hypotension for cesarean delivery: a randomized controlled trial, using up-down sequential allocation. Anesth Analg. 2024. doi:10.1213/ANE.0000000000007231. Roofthooft E, Rawal N, Van de Velde M. Current status of the combined spinal-epidural technique in obstetrics and surgery. Best Pract Res Clin Anaesthesiol. 2023;37:189-98. Rao WY, Xu F, Dai SB, Mei Z, Chen XP, Lv CC, et al. Comparison of dural puncture epidural, epidural and combined spinal-epidural anesthesia for cesarean delivery: a randomized controlled trial. Drug Des Devel Ther. 2023;17:2077-85. 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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-6644561","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":469850583,"identity":"83667482-17b6-4fab-88ee-3c336f96e04b","order_by":0,"name":"Rui Ma","email":"","orcid":"","institution":"the International Peace Maternity and Child Health Hospital","correspondingAuthor":false,"prefix":"","firstName":"Rui","middleName":"","lastName":"Ma","suffix":""},{"id":469850584,"identity":"8382613f-8ac4-44d3-ba59-289e9d2234e7","order_by":1,"name":"Tao Xu","email":"","orcid":"","institution":"the International Peace Maternity and Child Health Hospital","correspondingAuthor":false,"prefix":"","firstName":"Tao","middleName":"","lastName":"Xu","suffix":""},{"id":469850585,"identity":"c4ab94d2-2c44-4d02-8f9e-0c700bfa9c01","order_by":2,"name":"Shanshan Ye","email":"","orcid":"","institution":"the International Peace Maternity and Child Health Hospital","correspondingAuthor":false,"prefix":"","firstName":"Shanshan","middleName":"","lastName":"Ye","suffix":""},{"id":469850586,"identity":"02b60c0c-8659-4485-a29b-f05bc4e60247","order_by":3,"name":"Liqiang Zheng","email":"","orcid":"","institution":"the International Peace Maternity and Child Health Hospital","correspondingAuthor":false,"prefix":"","firstName":"Liqiang","middleName":"","lastName":"Zheng","suffix":""},{"id":469850587,"identity":"0bf29480-0e19-4e93-81be-89af817dc313","order_by":4,"name":"Jing Zheng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACeygtz89++OCDhIoawloMG6D0zJ60ZIMHZ44R1mJwAEInbLihYyb5sIWZCC23DzB+LqioSzC4wWNWkdjAxsDf3p2AX8u5BGbpGWcOg7XcSNwhwyBx5uwG/FrOMDBI87YdgGo5w8ZgIJFLUAvzb95/EIcVJLYxE6WFTZq3gRnsfQaitBj2MLBZ8xw7DA5kiYQzx3gI+sWeh4H5Nk9NHTgqP/6oqJHjb+/Fr4WBgf8DCpeHgPJRMApGwSgYBcQAAH20SWRrnbJHAAAAAElFTkSuQmCC","orcid":"","institution":"the International Peace Maternity and Child Health Hospital","correspondingAuthor":true,"prefix":"","firstName":"Jing","middleName":"","lastName":"Zheng","suffix":""}],"badges":[],"createdAt":"2025-05-12 08:38:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6644561/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6644561/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84685045,"identity":"e29ac04f-107a-48d2-b79c-9940ab5d4d2d","added_by":"auto","created_at":"2025-06-16 08:52:52","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":254731,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart of the study\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-6644561/v1/f86e0e15bb125c3c8627a25b.png"},{"id":84686587,"identity":"7226e090-3973-4dd2-87ac-6470c1be3baa","added_by":"auto","created_at":"2025-06-16 09:00:52","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":149983,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between IAP and decrease in SAP\u003c/p\u003e\n\u003cp\u003eThe decrease in SAP = baseline SAP–lowest SAP. The solid line represents the linear regression line, and the dotted lines represent the 95% confidence intervals.\u003c/p\u003e\n\u003cp\u003eSAP: systolic arterial pressure; IAP: intra-abdominal pressure.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-6644561/v1/d097185f2baab5ebf75c955e.png"},{"id":84685048,"identity":"f6c953a9-d7ce-4e93-ac6a-4e9fa09f9497","added_by":"auto","created_at":"2025-06-16 08:52:52","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":150284,"visible":true,"origin":"","legend":"\u003cp\u003eROC curve for IAP\u003c/p\u003e\n\u003cp\u003eROC: receiver operating characteristic; IAP: intra-abdominal pressure\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-6644561/v1/25839d4545fa742ad4848f14.png"},{"id":84685053,"identity":"a1c68425-e347-46ad-85de-fb64a676ee64","added_by":"auto","created_at":"2025-06-16 08:52:52","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":192462,"visible":true,"origin":"","legend":"\u003cp\u003eChanges in SAP and HR after spinal anesthesia between the normal and high IAP groups\u003c/p\u003e\n\u003cp\u003eThe left panel illustrates the changes in SAP over 12 min after spinal anesthesia induction in both the groups. Significant differences in SAP between the two groups were observed at 1, 2, 3, 4, 5, 6, 10, 11, and 12 min after spinal anesthesia induction (*\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). The right panel illustrates the changes in HR over 12 min after spinal anesthesia induction in both groups. The normal IAP group is represented by orange circular symbols (mean values), with adjacent orange bands indicating the standard deviation. The high IAP group is represented by green triangular symbols (mean values), with adjacent green bands indicating the standard deviation.\u003c/p\u003e\n\u003cp\u003eSAP: systolic arterial pressure; HR: heart rate; IAP: intra-abdominal pressure.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-6644561/v1/4a7be62fb5a3975a284f220e.png"},{"id":91432707,"identity":"e88ad8d8-306b-41ed-9ead-0f5ae30fe1aa","added_by":"auto","created_at":"2025-09-16 12:32:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1460681,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6644561/v1/5a5efbe5-9a78-43bd-aebd-3357d6d772b0.pdf"},{"id":84685051,"identity":"af88be54-cea6-4935-b3fd-a29d6f736c3b","added_by":"auto","created_at":"2025-06-16 08:52:52","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2333651,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6644561/v1/efc7ce2fe128a43f8945c336.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Association Between Intra-Abdominal Pressure and Post-Spinal Hypotension During Cesarean Delivery: A Prospective Observational Study","fulltext":[{"header":"BACKGROUND","content":"\u003cp\u003eHypotension after the induction of spinal anesthesia during cesarean delivery occurs in 50\u0026thinsp;\u0026minus;\u0026thinsp;70% of parturients\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. This complication is mainly caused by a rapid decline in peripheral circulation resistance due to sympathetic nervous system block and increased uterine pressure on the inferior vena cava (IVC), which exacerbates post-spinal hypotension\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Consequently, adverse effects\u0026mdash;including nausea, vomiting, dyspnea, and fetal distress\u0026mdash;can occur in both the mother and fetus. Therefore, effective prediction of post-spinal hypotension is essential for ensuring maternal and neonatal safety and increasing maternal comfort.\u003c/p\u003e \u003cp\u003eIntra-abdominal pressure (IAP) is defined as the steady state of pressure within the abdominal cavity\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. IAP increases significantly with the growing fetus and amniotic fluid during pregnancy\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Several studies\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e have validated that increased IAP could aggravate the pressure on the IVC via direct compression. The size of the uterus or diameter of the compressed IVC cannot be easily measured during the third trimester, while IAP could be measured using a transurethral catheter before cesarean delivery. Thus, we hypothesized that baseline IAP could be associated with post-spinal hypotension caused by the compression of the IVC.\u003c/p\u003e \u003cp\u003eHence, in the current study, we aimed to identify the relationship between IAP and post-spinal hypotension as well as determine the cutoff value of IAP and its potential to predict hypotension after the induction of spinal anesthesia during cesarean delivery. These findings will enable personalized strategies for parturients before anesthesia.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003e This prospective observational study was approved by the Medical Research Ethics Committee of the International Peace Maternity and Child Health Hospital, Shanghai, China (Chairperson Zhiwei Liu) on September 19, 2023 (GKLW-A-2023-035-01). The study was designed in accordance with the applicable STROBE guidelines. Written informed consent was obtained from all the participants after recruitment.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eInclusion and exclusion criteria\u003c/h2\u003e \u003cp\u003eEighty-six full-term parturients with singleton pregnancies, aged 20\u0026ndash;40 years, with heights ranging from 156 to 170 cm and an American Society of Anesthesiologists physical status classification of II, and who underwent elective cesarean delivery with combined spinal-epidural (CSE) anesthesia in the International Peace Maternity and Child Health Hospital were recruited between November 22, 2023 and February 26, 2024.\u003c/p\u003e \u003cp\u003eThe exclusion criteria were as follows: contraindications to spinal anesthesia, allergy to ropivacaine, preeclampsia or hypertension, underlying valvular disease detected by preoperative echocardiography, multiple pregnancies, body mass index [BMI] of \u0026gt;\u0026thinsp;35 kg/m\u003csup\u003e2\u003c/sup\u003e, active labor, emergency cesarean delivery, and parturient refusal. Parturients with difficult epidural puncture and an anesthesia level below T6 before surgery were also withdrawn after enrolment.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStudy design\u003c/h3\u003e\n\u003cp\u003eAll parturients fasted overnight and were administered 500 mL crystalloid solution through an 18 G cannula within half an hour after entering the operating room. Routine monitoring included non-invasive blood pressure measurements, electrocardiography, and pulse oximetry, which was performed continuously. Consecutive systolic arterial pressure (SAP) and heart rate (HR) values were recorded in the supine position every minute; the average of the first two readings was treated as the baseline. Parturients with an SAP of \u0026gt;\u0026thinsp;140 mm Hg were excluded for suspected hypertension.\u003c/p\u003e\n\u003ch3\u003eMeasurement of IAP\u003c/h3\u003e\n\u003cp\u003eAs routine practice, a transurethral 16 Fr Foley catheter was inserted to drain the bladder before anesthesia. Pressure measurements were recorded in the supine position using the intravesical pressure measurement system, according to the method described in the World Society of the Abdominal Compartment Syndrome (WSACS) guidelines\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The pressure measurement kit (Exadyn Combitrans Monitoring Set; B. Braun Melsungen AG, Germany) connected to a monitor (IntelliVue MP50; Philips Medical Systems Boeblingen GmbH, Germany) was used to determine the IAP value. The mid-axillary level in the supine position and a 25 mL bladder inflation volume were considered the zero reference. The first steady value was considered the IAP value. IAP and other maternal characteristics were measured and recorded by a trained researcher; the anesthesiologist and the parturients were blinded to these measurements.\u003c/p\u003e\n\u003ch3\u003eProcedure for anesthesia induction\u003c/h3\u003e\n\u003cp\u003eAn anesthesiologist with over 15 years of experience routinely performed the CSE puncture at the L3\u0026ndash;4 interspace with the parturient in the right lateral position. A 17 G Tuohy needle was used, followed by the insertion of a 27 G Whitacre needle through the Tuohy needle to access the subarachnoid space. Upon identification of cerebrospinal fluid, 15 mg 0.5% plain ropivacaine was injected. An epidural catheter was then inserted 4 cm into the epidural space. Subsequently, the parturient was moved to the supine position, and a 30-degree wedge was placed under the right hip. The upper anesthesia level was assessed by pinprick; parturients whose anesthesia level remained below T6 at the beginning of surgery were withdrawn from the study. SAP and HR were recorded every minute for 12 min before delivery and then every 5 min until the end of surgery.\u003c/p\u003e \u003cp\u003eHypotension was defined as a drop in SAP of \u0026gt;\u0026thinsp;20% from the baseline value. A rescue dose of 50 \u0026micro;g phenylephrine was administered upon the occurrence of hypotension. Bradycardia, defined as an HR of \u0026lt;\u0026thinsp;50 beats/min, was treated using intravenous atropine (0.5 mg).\u003c/p\u003e \u003cp\u003eAfter delivery, Apgar scores at 1 and 5 min, along with neonatal body weights, were recorded. An obstetrician immediately collected 1 mL umbilical artery (UA) blood, and blood gas assessments were performed using a blood gas analyzer (Edan i15 Blood Gas Analyzer; ICEN, Guangdong, China) with an iSTAT BG10 test cartridge.\u003c/p\u003e \u003cp\u003eThe primary outcome was the association between IAP and post-spinal hypotension during cesarean section. Maternal and obstetric characteristics included age, height, weight, BMI, gravidity, parity, amniotic fluid index, expected fetal weight by ultrasound within 1 week before cesarean section, uterine height, abdominal circumference, total doses of phenylephrine and atropine administered, upper anesthesia level, incision\u0026ndash;delivery interval, neonatal body weight, Apgar scores at 1 min and 5 min, pH and base excess of UA blood, and maternal adverse symptoms.\u003c/p\u003e\n\u003ch3\u003eSample size calculation and statistical analysis\u003c/h3\u003e\n\u003cp\u003eBased on clinical experience, the probability of hypotension occurring during cesarean delivery after administering 15 mg 0.5% plain ropivacaine into the subarachnoid space is approximately 50%\u003csup\u003e8\u003c/sup\u003e. Assuming equal numbers of parturients with and without hypotension and using IAP as an indicator, with α\u0026thinsp;=\u0026thinsp;0.05, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve for IAP was 0.8 with a confidence interval (CI) width of 0.2. The sample size calculated using Power Analysis and Sample Size 2021 was 78. Considering a dropout rate of 10%, this study required at least 86 parturients.\u003c/p\u003e \u003cp\u003eThe Tidyverse package was used for data cleaning, Table One package for summarizing baseline characteristics, car package for exploring collinearity issues, pROC package for generating ROC curves, base R package for fitting logistic regression models, and ggplot2 package for creating additional plots. All analyses were conducted using R 4.4.1 (R Foundation for Statistical Computing, Vienna, Austria). Significance was defined as a \u003cem\u003eP\u003c/em\u003e-value of \u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003cp\u003eThe Kolmogorov\u0026ndash;Smirnov test was used for determining whether variables were normally distributed. Maternal and obstetric characteristic data are presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviations for normally distributed continuous variables, medians (P25, P75) for skewed continuous variables, and percentages for categorical variables.\u003c/p\u003e \u003cp\u003eA scatterplot was constructed to assess the linearity between IAP and the decrease in SAP, and a linear correlation was plotted. Spearman\u0026rsquo;s rank correlation was used to assess the correlations between IAP measured before anesthesia and the decrease in SAP from baseline.\u003c/p\u003e \u003cp\u003eAn ROC curve was then constructed to assess suitable diagnostic thresholds based on the Youden index, balancing specificity and sensitivity.\u003c/p\u003e \u003cp\u003eTwo steps of logistic regression were used in this study. Both univariate and multivariable logistic regressions were used in step 1 to evaluate the predictive value of IAP for hypotension after anesthesia. The following factors were first included in the univariate regressions: IAP, age, BMI, gravidity, gestational week, expected weight of baby by ultrasound, uterine height, and abdominal circumference that may relate to post-spinal hypotension; the odds ratios (ORs) and their 95% CIs for hypotension were determined with IAP as a continuous variable (1 mm Hg). Subsequently, the variables that were univariably associated (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) with hypotension, along with clinically relevant variables, were included in the multivariable model building; ORs with 95% CIs were also reported. The degree of multicollinearity using the variance inflation factor (VIF) was assessed, and variables with a VIF of \u0026gt;\u0026thinsp;10 were dropped. In step 2, only univariate logistic regression was performed to evaluate the ORs and their CIs, with the IAP categorized into two groups (\u0026lt;\u0026thinsp;12.5 mm Hg and \u0026ge;\u0026thinsp;12.5 mm Hg, using the best threshold from the ROC curve based on the Youden index).\u003c/p\u003e \u003cp\u003eComparisons between parturients with normal and high IAP (IAP\u0026thinsp;\u0026lt;\u0026thinsp;12.5 mm Hg or \u0026ge;\u0026thinsp;12.5 mm Hg) were performed using the Student \u003cem\u003et\u003c/em\u003e-test, Mann\u0026ndash;Whitney U test, and χ\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e test.\u003c/p\u003e \u003cp\u003eDifferences in SAP and HR for a successive 12 min after the induction of spinal anesthesia between the groups with normal and high IAP were assessed using two-way analysis of variance and the Bonferroni post-hoc test.\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003ePatient characteristics\u003c/h2\u003e \u003cp\u003eA total of 122 parturients were recruited, of whom 86 met the inclusion criteria and participated in the current study. Eighteen parturients underwent emergency cesarean sections, nine had preeclampsia, five had multiple pregnancies, one had morbid obesity (BMI\u0026thinsp;\u0026ge;\u0026thinsp;36 kg/m\u003csup\u003e2\u003c/sup\u003e), and three refused to participate, resulting in their exclusion from the study. Additionally, the data of three parturients were excluded from further analysis because of inadequate blockade of anesthesia. The analysis was based on the remaining 83 data sets (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The maternal and obstetric characteristics of all the parturients, and categorized into hypotension (n\u0026thinsp;=\u0026thinsp;42) and non-hypotension (n\u0026thinsp;=\u0026thinsp;40) groups, are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The mean IAP before anesthesia induction was higher in the hypotension than in the non-hypotension group (14.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3 mm Hg vs. 10.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3 mm Hg, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The distribution of measured IAP showed differences between the two groups. Other characteristics that also significantly differed between the groups included height, BMI, expected fetal weight by ultrasound, uterine height, and abdominal circumference.\u003c/p\u003e \u003cp\u003e \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\u003eMaternal and obstetric characteristics of all parturients and categorized into hypotension and non-hypotension groups\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=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal (N\u0026thinsp;=\u0026thinsp;83)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNon-hypotension (N\u0026thinsp;=\u0026thinsp;40)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHypotension (N\u0026thinsp;=\u0026thinsp;43)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (yr)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.012\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e162.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e163.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e161.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e70.5\u0026thinsp;\u0026plusmn;\u0026thinsp;9.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e68.7\u0026thinsp;\u0026plusmn;\u0026thinsp;9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e72.2\u0026thinsp;\u0026plusmn;\u0026thinsp;9.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.090\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\u003e26.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGestational week (wk)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e38.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.232\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGravidity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2 (1, 3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (1, 2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (1, 3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.050\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0, 1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0, 1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0 (0, 1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.570\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAFI (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e129.2\u0026thinsp;\u0026plusmn;\u0026thinsp;32.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e127.1\u0026thinsp;\u0026plusmn;\u0026thinsp;33.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e131.1\u0026thinsp;\u0026plusmn;\u0026thinsp;31.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.574\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExpected foetal weight (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3274.0\u0026thinsp;\u0026plusmn;\u0026thinsp;440.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3140.6\u0026thinsp;\u0026plusmn;\u0026thinsp;421.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3398.1\u0026thinsp;\u0026plusmn;\u0026thinsp;426.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.007\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUterine height (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36.9\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e38.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbdominal circumference (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e96.2\u0026thinsp;\u0026plusmn;\u0026thinsp;7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e93.9\u0026thinsp;\u0026plusmn;\u0026thinsp;6.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e98.5\u0026thinsp;\u0026plusmn;\u0026thinsp;7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIAP (mmHg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIAP, n (%)\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=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;12 mmHg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30 (36.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e28 (70)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (4.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u0026ndash;15 mmHg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e34 (41.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (25)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24 (55.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026gt;15 mmHg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19 (22.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17 (39.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eValues are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD or median (IQR)\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eIQR: interquartile range; SD\u0026thinsp;=\u0026thinsp;standard deviation;BMI: body mass index; AFI: Amniotic Fluid Index; IAP: Intra-abdominal Pressure.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCorrelation between IAP and decrease in SAP\u003c/h3\u003e\n\u003cp\u003eA linear correlation was observed between IAP and the decrease in SAP from baseline (\u003cem\u003er\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.455; \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eROC analysis and cutoff value for IAP\u003c/h2\u003e \u003cp\u003eThe ROC analysis revealed that IAP effectively detected parturients at risk of hypotension, with an AUC of 0.92 (95% CI: 0.85 to 0.99, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The optimal IAP cutoff was 12.5 mm Hg, yielding a sensitivity of 92%, specificity of 88%, positive predictive value of 93%, and negative predictive value of 88% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eLogistic regression analysis of IAP and risk of post-spinal hypotension\u003c/h2\u003e \u003cp\u003eBoth univariate and multivariable logistic regression were used in step 1. Parturients with a higher IAP, BMI, expected weight of the baby by ultrasound, uterine height, and abdominal circumference were at risk of developing hypotension after the induction of spinal anesthesia, while advanced age emerged as a protective factor against developing hypotension through univariate logistic regression. In the multivariable model, IAP was found to be an independent risk factor after adjusting for the variables identified in the univariate logistic regression. For every 1 mm Hg increase in IAP, parturients had 2.24 times the odds of developing post-spinal hypotension (95% CI: 1.6 to 3.6, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\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\u003eUnivariable and multivariable analysis of risk factors associated with hypotension\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 \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eUnivariate\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eMultivariate\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\u003eOR (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ep- value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOR (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep- value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStep 1\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 \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIAP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.26 (1.68\u0026ndash;3.35)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.24 (1.6\u0026ndash;3.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\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\u003e0.85 (0.74\u0026ndash;0.97)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.85 (0.67\u0026ndash;1.04)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.152\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\u003e1.23 (1.07\u0026ndash;1.44)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.14 (0.79\u0026ndash;1.69)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.504\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003egravidity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.36 (0.96\u0026ndash;2.01)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.093\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.7 (1.02\u0026ndash;3.08)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.055\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGestational week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.54 (0.97\u0026ndash;2.52)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.076\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.99 (0.38\u0026ndash;2.55)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.986\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExpect weight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.16 (1.04\u0026ndash;1.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.18 (0.92\u0026ndash;1.55)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.204\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUterine height\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.19 (1.05\u0026ndash;1.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.09 (0.88\u0026ndash;1.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.452\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbdominal circumference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.11 (1.03\u0026ndash;1.19)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.95 (0.78\u0026ndash;1.14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.601\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStep 2\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 \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIAP\u0026thinsp;\u0026lt;\u0026thinsp;12.5 mmHg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (ref)\u003c/p\u003e \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\u003eN/A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eN/A\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIAP\u0026thinsp;\u0026ge;\u0026thinsp;12.5 mmHg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e93.73 (24.02\u0026ndash;511.66)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\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 \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eBMI: body mass index; IAP: Intra-abdominal Pressure.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn step 2, univariate logistic regression was used to evaluate the ORs and their CIs, with IAP categorized into normal and high groups (\u0026lt;\u0026thinsp;12.5 mm Hg and \u0026ge;\u0026thinsp;12.5 mm Hg). Parturients with a high IAP had 93.73 times the odds of developing post-spinal hypotension than did those with a normal IAP (95% CI: 24.02 to 511.66, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eHemodynamic changes after spinal analgesia induction based on IAP\u003c/h2\u003e \u003cp\u003eParturients with both a high and normal IAP experienced a decrease in SAP after the induction of spinal analgesia. Parturients with an IAP of \u0026ge;\u0026thinsp;12.5 mm Hg exhibited a lower SAP than did those with an IAP of \u0026lt;\u0026thinsp;12.5 mm Hg at 1, 2, 3, 4, 5, 6, 10, 11, and 12 min after spinal anesthesia induction. HRs were not significantly different between the two IAP groups after the induction of spinal anesthesia (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eClinical outcomes\u003c/h2\u003e \u003cp\u003eParturients with an IAP of \u0026ge;\u0026thinsp;12.5 mm Hg with a greater occurrence (92.7% vs. 11.9%, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) of post-spinal hypotension required higher doses of phenylephrine (0 [0, 0] vs. 100 [50, 100] \u0026micro;g, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) or longer rescue times with phenylephrine (0 [0, 0] vs. 1 [1, 2], P\u0026thinsp;=\u0026thinsp;0.005) before delivery. The incidence of nausea was also higher in parturients with an IAP of \u0026ge;\u0026thinsp;12.5 mm Hg (0% vs. 17.1%, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.005). Parturients with an IAP of \u0026ge;\u0026thinsp;12.5 mm Hg exhibited a greater fetal birth weight (3513.7\u0026thinsp;\u0026plusmn;\u0026thinsp;480.8 vs. 3221.8\u0026thinsp;\u0026plusmn;\u0026thinsp;493.7 g, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.008) than did those with an IAP of \u0026lt;\u0026thinsp;12.5 mm Hg. The results of the UA blood analysis and Apgar scores at 1 and 5 min did not differ between the two groups (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\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\u003eMaternal and neonatal observations between normal IAP (IAP\u0026thinsp;\u0026lt;\u0026thinsp;12.5mmHg) and high IAP (IAP\u0026thinsp;\u0026ge;\u0026thinsp;12.5mmHg) groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNormal IAP\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHigh IAP\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;41)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePost-spinal hypotension, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (11.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38 (92.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePhenylephrine dose (\u0026micro;g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0, 0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100 (50,100)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePhenylephrine times\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0, 0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (1, 2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDyspnoea, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (9.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.055\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNausea, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (17.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInduction-delivery interval (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.450\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe upper sensory level\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (4, 4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (4, 4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.337\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBaby birth weight (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3221.8\u0026thinsp;\u0026plusmn;\u0026thinsp;493.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3513.7\u0026thinsp;\u0026plusmn;\u0026thinsp;480.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApgar scores at 1 minute\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (10, 10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (10, 10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.494\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApgar scores at 5 minutes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (10, 10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (10, 10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN/A\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.342\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBE (mmol/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-2.68\u0026thinsp;\u0026plusmn;\u0026thinsp;1.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-2.86\u0026thinsp;\u0026plusmn;\u0026thinsp;1.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.681\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, number (percentage), or median (IQR).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eIQR: interquartile range; SD: standard deviation; BE: base excess.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eIn this study, IAP before spinal anesthesia induction was measured to determine the potential association between IAP and post-spinal hypotension. We observed that IAP was associated with the occurrence of hypotension after the induction of spinal anesthesia, and a cutoff value of \u0026ge;\u0026thinsp;12.5 mm Hg could predict subsequent hypotension. Further, an increased IAP may be associated with a higher incidence and severity of hypotension before delivery.\u003c/p\u003e \u003cp\u003ePost-spinal hypotension primarily occurs in two ways: blockade of the sympathetic nervous system after spinal anesthesia induction, which reduces peripheral vascular resistance, and compression of the uterus on the IVC after abdominal muscle relaxation\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Both these mechanisms are involved in reducing the amount of blood that returns to the heart. Previous methods for predicting the occurrence of hypotension after spinal anesthesia induction were primarily based on the assessment of maternal autonomic nervous system function before anesthesia induction\u003csup\u003e\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. However, an ideal prediction is difficult to achieve, as the assessment of autonomic nervous system function is influenced by many factors, such as maternal body movement, body temperature, and anxiety. Therefore, these methods are rarely used in clinical practice.\u003c/p\u003e \u003cp\u003eThe mechanism by which IAP predicts hypotension after spinal anesthesia induction may involve its reflection of uterine compression on the IVC, as previously mentioned. The authors of several studies outside the field of obstetric anesthesia have confirmed that IAP induces hypotension through IVC compression. Two studies have revealed that a prolonged increase in IAP may reduce cardiac output owing to direct compression of the IVC and portal vein\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Stacey et al.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e and Hirabayashi et al.\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e validated that an increased IAP could aggravate the pressure on the IVC via direct compression. An animal experiment\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e further revealed that a higher IAP (\u0026gt;\u0026thinsp;15\u0026ndash;20 mm Hg) may be associated with a lower additional gain in volume expansion but more hemodynamic side effects in rabbits.\u003c/p\u003e \u003cp\u003eAlthough current research on the correlation between IAP and maternal hypotension after spinal anesthesia induction remains limited, observations in pregnant women in the third trimester provide indirect evidence that supine positioning often triggers hypotension and fetal distress\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. This finding suggests that pregnancy-related IAP elevation intensifies IVC compression. Since sympathetic blockade is absent in this scenario, IVC compression stands as the sole plausible explanation for third-trimester hypotension. Notably, pregnancy inherently constitutes a state of progressive IAP increase\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, making this physiological mechanism particularly relevant in obstetric anesthesia.\u003c/p\u003e \u003cp\u003eTherefore, we have reason to believe that the higher the baseline IAP, the more pronounced the compression of the IVC, which further exacerbates maternal hypotension after spinal anesthesia induction. In our study, we also found that as IAP increased, the risk of hypotension significantly rose, and the magnitude of the drop in blood pressure was more substantial. These findings corroborate our above hypothesis regarding the mechanism of hypotension occurrence after spinal anesthesia induction during cesarean section.\u003c/p\u003e \u003cp\u003eDespite the widespread use of prophylactic vasopressor agents\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, predicting the risk of hypotension after the induction of spinal anesthesia seems less important. However, we believe that owing to the high predictive value of IAP before anesthesia induction for identifying hypotension, measuring IAP before anesthesia induction can not only help to reduce the prophylactic use of vasopressors in low-risk parturients but also, when encountering high-risk parturients with a significantly elevated IAP, facilitate the provision of a more comprehensive anesthesia plan. This may include more detailed pre-anesthesia education on adverse reactions related to hypotension, changing the anesthesia induction method (using epidural anesthesia or commencing with a lower spinal dose of local anesthetics with CSE), further shortening the time interval from anesthetic administration to fetal delivery\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e in high-risk parturients, or reducing or discontinuing the minute dosage of prophylactic vasopressors in low-risk parturients. These measures can offer a relatively comfortable anesthesia experience for parturients.\u003c/p\u003e \u003cp\u003eOur study has several strengths. First, clinical consistency―the study results demonstrate only minor discrepancies when compared to the intra-abdominal hypertension diagnostic criteria established by the WSACS\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. This confirms the dual clinical value of IAP as a predictive marker for hypotension following spinal anesthesia induction; it not only forecasts the risk of hypotension but also exhibits a significant correlation with the magnitude of blood pressure decline. Second, operational feasibility\u0026mdash;in obstetric practice, urinary catheterization is routinely performed preoperatively for parturients undergoing cesarean sections. Consequently, IAP monitoring requires no additional invasive procedures, significantly lowering the technical implementation barrier. Finally, device versatility\u0026mdash;existing arterial pressure monitoring kits are sufficient for IAP measurement, eliminating the need for specialized equipment. With the widespread adoption of this technique, the development of intelligent urinary catheters integrated with pressure-monitoring capabilities is anticipated, thereby optimizing clinical workflows.\u003c/p\u003e \u003cp\u003eHowever, our study also has some limitations. First, the WSACS guidelines recommend the supine position for IAP measurements, with no specific reference to parturients. Therefore, the supine position was also used in this study. However, the parturient was moved to the supine position with a wedge placed under the right hip after anesthesia induction. IAP values might change with different positions. It is assumed that for a parturient in the lateral decubitus position, if the IAP exceeds the normal level when lying supine, the vertical pressure exerted on the IVC and abdominal aorta would also be elevated when the parturient lies on their side at the same angle. Second, we imposed some limitations on the height and weight of the enrolled parturients, which limits the generalizability of our results to specific populations while reducing selection bias.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eOur findings confirms that IAP is an independent risk factor for post-spinal hypotension during cesarean delivery. A cutoff value\u0026thinsp;\u0026ge;\u0026thinsp;12.5 mm Hg could predict subsequent hypotension, and a higher IAP may be associated with a higher incidence and severity of hypotension before delivery. Further studies and more convenient IAP measurement methods are needed to explore its clinical feasibility.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eAUC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003earea under the curve\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBMI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003ebody mass index\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eCI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003econfidence interval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eCSE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003ecombined spinal and epidural\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eHR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003eheart rate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eIAP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003eintra-abdominal pressure\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eIVC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003einferior vena cava\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eOR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003eodds ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eROC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003ereceiver operating characteristic\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSAP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003esystolic arterial pressure\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eUA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003eumbilical artery\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eVIF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003evariance inflation factor\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eWSACS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 416px;\"\u003e\n \u003cp\u003eWorld Society of the Abdominal Compartment Syndrome\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Medical Research Ethics Committee of the International Peace Maternity and Child Health Hospital, Shanghai, China (Chairperson Zhiwei Liu) on September 19, 2023 (GKLW-A-2023-035-01). Written informed consent was obtained from all the participants after recruitment.\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\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that underlie the results reported in this article and study protocol and the statistical analysis plan can be shared within 3 years following article publication with sound proposal. Proposals should be directed to [email protected].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSupport was provided by the Fund of the International Peace Maternity and Child Health Hospital, Shanghai, China (A 3-year Action Plan for Clinical Research Program, IPMCH2022CR-07).\u003c/p\u003e\n\u003cp\u003eAuthors\u0026rsquo; contributions\u003c/p\u003e\n\u003cp\u003eRM helped with the data acquisition, analysis, and interpretation; writing of the first draft; and approval of the final version of the manuscript. TX helped with data acquisition, writing of the first draft, and approval of the final version of the manuscript. SY helped with the data analysis and interpretation and approval of the final version of the manuscript. LZ helped with the data analysis and interpretation and approval of the final version of the manuscript. JZ helped with the study conception and design, data analysis and interpretation, revision of the manuscript for important intellectual content, and approval of the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank all the staff of\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003ethe Clinical Research Center, the International Peace Maternity and Child Health Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China, for their efforts and support in the study.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe study was pre-registered at http://www.chictr.org.cn on October 24, 2023 (ChiCTR2300076915), by Rui Ma, and the first patient was recruited on November 22, 2023.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eFitzgerald JP, Fedoruk KA, Jadin SM, Carvalho B, Halpern SH. Prevention of hypotension after spinal anaesthesia for caesarean section: a systematic review and network meta-analysis of randomised controlled trials. Anaesthesia. 2020;75:109-21.\u003c/li\u003e\n\u003cli\u003eSalama ER, Elkashlan M. Pre-operative ultrasonographic evaluation of inferior vena cava collapsibility index and caval aorta index as new predictors for hypotension after induction of spinal anaesthesia: a prospective observational study. Eur J Anaesthesiol. 2019;36:297-302.\u003c/li\u003e\n\u003cli\u003eOlerud S. Experimental studies on portal circulation at increased intra-abdominal pressure. Acta Physiol Scand Suppl. 1953;30:1-95.\u003c/li\u003e\n\u003cli\u003eJayasundara S, Goonewardene M, Dassanayake L. The association between maternal intra-abdominal pressure and hypertension in pregnancy. PLoS One. 2023;18:e0284230.\u003c/li\u003e\n\u003cli\u003eStacey T, Thompson JM, Mitchell EA, Ekeroma AJ, Zuccollo JM, McCowan LM. Association between maternal sleep practices and risk of late stillbirth: a case-control study. BMJ. 2011;342:d3403.\u003c/li\u003e\n\u003cli\u003eHirabayashi Y, Shimizu R, Fukuda H, Saitoh K, Igarashi T. Effects of the pregnant uterus on the extradural venous plexus in the supine and lateral positions, as determined by magnetic resonance imaging. Br J Anaesth. 1997;78:317-9.\u003c/li\u003e\n\u003cli\u003eKirkpatrick AW, Roberts DJ, De Waele J, Jaeschke R, Malbrain ML, De Keulenaer B, et al. Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome. Intensive Care Med. 2013;39:1190-206.\u003c/li\u003e\n\u003cli\u003eXu Z, Xu T, Zhao P, Ma R, Zhang M, Zheng J. Differential roles of the right and left toe perfusion index in predicting the incidence of postspinal hypotension during cesarean delivery. Anesth Analg. 2017;125:1560-6.\u003c/li\u003e\n\u003cli\u003eKundra P, Khanna S, Habeebullah S, Ravishankar M. Manual displacement of the uterus during Caesarean section. Anaesthesia. 2007;62:460-5.\u003c/li\u003e\n\u003cli\u003eLal J, Jain M, Rahul, Singh AK, Bansal T, Vashisth S. Efficacy of inferior vena cava collapsibility index and caval aorta index in predicting the incidence of hypotension after spinal anaesthesia- a prospective, blinded, observational study. Indian J Anaesth. 2023;67:523-9.\u003c/li\u003e\n\u003cli\u003eOuzounian JG, Masaki DI, Abboud TK, Greenspoon JS. Systemic vascular resistance index determined by thoracic electrical bioimpedance predicts the risk for maternal hypotension during regional anesthesia for cesarean delivery. Am J Obstet Gynecol. 1996;174:1019-25.\u003c/li\u003e\n\u003cli\u003eBoyle SL, Moodley A, Al Azazi E, Dinsmore M, Massicotte EM, Venkatraghavan L. Preoperative heart rate variability predicts postinduction hypotension in patients with cervical myelopathy: a prospective observational study. Neurol India. 2022;70:S269-75.\u003c/li\u003e\n\u003cli\u003eBolea J, L\u0026aacute;zaro J, Gil E, Rovira E, Remart\u0026iacute;nez JM, Laguna P, et al. Pulse rate and transit time analysis to predict hypotension events after spinal anesthesia during programmed cesarean labor. Ann Biomed Eng. 2017;45:2253-63.\u003c/li\u003e\n\u003cli\u003eToyama S, Kakumoto M, Morioka M, Matsuoka K, Omatsu H, Tagaito Y, et al. Perfusion index derived from a pulse oximeter can predict the incidence of hypotension during spinal anaesthesia for Caesarean delivery. Br J Anaesth. 2013;111:235-41.\u003c/li\u003e\n\u003cli\u003eRossi A, Cornette J, Johnson MR, Karamermer Y, Springeling T, Opic P, et al. Quantitative cardiovascular magnetic resonance in pregnant women: cross-sectional analysis of physiological parameters throughout pregnancy and the impact of the supine position. J Cardiovasc Magn Reson. 2011;13:31.\u003c/li\u003e\n\u003cli\u003eAntoniou EA, Kairi E, Margonis GA, Andreatos N, Sasaki K, Damaskos C, et al. Effect of increased intra-abdominal pressure on liver histology and hemodynamics: an experimental study. In Vivo. 2018;32:85-91.\u003c/li\u003e\n\u003cli\u003eS\u0026uuml;mpelmann R, Schuerholz T, Marx G, Jesch NK, Osthaus WA, Ure BM. Hemodynamic changes during acute elevation of intra-abdominal pressure in rabbits. Paediatr Anaesth. 2006;16:1262-7.\u003c/li\u003e\n\u003cli\u003eSaini BS, Ducas R, Darby JRT, Marini D, Sun L, Macgowan CK, et al. Feasibility of MRI assessment of maternal-fetal oxygen transport and consumption relative to maternal position in healthy late gestational pregnancies. J Physiol. 2023;601:5413-36.\u003c/li\u003e\n\u003cli\u003eJani D, Clark A, Couper S, Thompson JMD, David AL, Melbourne A, et al. The effect of maternal position on placental blood flow and fetoplacental oxygenation in late gestation fetal growth restriction: a magnetic resonance imaging study. J Physiol. 2023;601:5391-411.\u003c/li\u003e\n\u003cli\u003eArora V, Tyagi A, Ramanujam M, Luthra A. Intraabdominal pressure in non-laboring preeclamptic vs normotensive patients undergoing cesarean section: a prospective observational study. Acta Obstet Gynecol Scand. 2020;99:1031-8.\u003c/li\u003e\n\u003cli\u003eOzkan Seyhan T, Orhan-Sungur M, Basaran B, Savran Karadeniz M, Demircan F, Xu Z, et al. The effect of intra-abdominal pressure on sensory block level of single-shot spinal anesthesia for cesarean section: an observational study. Int J Obstet Anesth. 2015;24:35-40.\u003c/li\u003e\n\u003cli\u003eBelin O, Casteres C, Alouini S, Le Pape M, Dupont A, Boulain T. Manually controlled, continuous infusion of phenylephrine or norepinephrine for maintenance of blood pressure and cardiac output during spinal anesthesia for cesarean delivery: a double-blinded randomized study. Anesth Analg. 2023;136:540-50.\u003c/li\u003e\n\u003cli\u003eKhatoon F, Kocarev M, Fernando R, Naz A, Khalid F, Ibrahim Abdalla EO, et al. Optimal infusion rate of norepinephrine for prevention of spinal hypotension for cesarean delivery: a randomized controlled trial, using up-down sequential allocation. Anesth Analg. 2024. doi:10.1213/ANE.0000000000007231.\u003c/li\u003e\n\u003cli\u003eRoofthooft E, Rawal N, Van de Velde M. Current status of the combined spinal-epidural technique in obstetrics and surgery. Best Pract Res Clin Anaesthesiol. 2023;37:189-98.\u003c/li\u003e\n\u003cli\u003eRao WY, Xu F, Dai SB, Mei Z, Chen XP, Lv CC, et al. Comparison of dural puncture epidural, epidural and combined spinal-epidural anesthesia for cesarean delivery: a randomized controlled trial. Drug Des Devel Ther. 2023;17:2077-85.\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":"intra-abdominal hypertension, cesarean delivery, spinal anesthesia, hypotension","lastPublishedDoi":"10.21203/rs.3.rs-6644561/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6644561/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003ePost-spinal hypotension can be exacerbated by increased pressure on the inferior vena cava during cesarean delivery. We examined the relationship between intra-abdominal pressure and post-spinal hypotension.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis prospective study included 83 parturients, aged 20\u0026ndash;40 years, who underwent elective cesarean delivery in a tertiary level A maternity and child health hospital. Intra-abdominal pressure was measured before the induction of spinal analgesia. A receiver operating characteristic curve was used to determine the optimum cutoff value of intra-abdominal pressure for post-spinal hypotension. Univariable and multivariable logistic regression analyses were performed to explore the association between intra-abdominal pressure or binary classification based on the optimal intra-abdominal pressure cutoff value and hypotension after spinal anesthesia.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eA linear correlation was observed between the decrease in systolic arterial pressure from baseline and intra-abdominal pressure (r\u0026thinsp;=\u0026thinsp;0.455; \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The area under the receiver operating characteristic curve for predicting post-spinal hypotension was 0.92 (95% confidence interval: 0.85\u0026ndash;0.99), with an optimal cutoff of 12.5 mm Hg. Intra-abdominal pressure was revealed as an independent risk factor for post-spinal hypotension in the logistic regression analysis. Parturients with an intra-abdominal pressure of \u0026ge;\u0026thinsp;12.5 mm Hg had 93.73 times the odds of developing post-spinal hypotension than those with an intra-abdominal pressure\u0026thinsp;\u0026lt;\u0026thinsp;12.5 mm Hg. The occurrence (92.7% vs. 11.9%, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) of post-spinal hypotension was different between the two intra-abdominal pressure groups.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eIntra-abdominal pressure was an independent risk factor for post-spinal hypotension during cesarean delivery. A cutoff value of \u0026ge;\u0026thinsp;12.5 mm Hg could predict subsequent hypotension, while higher intra-abdominal pressure may be associated with a higher incidence of and more severe hypotension before delivery.\u003c/p\u003e","manuscriptTitle":"Association Between Intra-Abdominal Pressure and Post-Spinal Hypotension During Cesarean Delivery: A Prospective Observational Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-16 08:52:47","doi":"10.21203/rs.3.rs-6644561/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":"8f2e1474-d4ee-4c50-a178-37327918b9da","owner":[],"postedDate":"June 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-16T12:24:06+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-16 08:52:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6644561","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6644561","identity":"rs-6644561","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}