Influence of different anesthetic depth on postoperative delirium in elderly pre-frail patients undergoing abdominal surgery

Influence of different anesthetic depth on postoperative delirium in elderly pre-frail patients undergoing abdominal surgery | 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 Influence of different anesthetic depth on postoperative delirium in elderly pre-frail patients undergoing abdominal surgery Rongman Chen, Pengfei Hou, Wanxin Liu, Haiqi Mi, Shuaiying Jia, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5950908/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 28 Jul, 2025 Read the published version in Perioperative Medicine → Version 1 posted 13 You are reading this latest preprint version Abstract Purpose Monitoring anesthetic depth may reduce the incidence of postoperative delirium in patients undergoing general anesthesia. This study investigated the impact of varying readings of Cerebral State Index (CSI) on postoperative delirium in elderly pre-frail patients undergoing abdominal surgery. Methods A total of 150 elderly pre-frail patients aged over 65 years scheduled for selective abdominal surgery under general anesthesia were enrolled. Pre-frailty was defined as a 5-Item Modified Frailty Index (mFI-5) score of 1–2. Patients in the light anesthesia (LA) group were maintained a CSI value between 50–59, while patients in the deep anesthesia (DA) group were maintained a CSI value between 40–49. The incidence of delirium within three days postoperatively, as well as visual analog scale (VAS) scores, postoperative nausea, vomiting, and the 15-item quality of recovery (QoR-15) scale scores on the first postoperative day were recorded and compared. Results The incidence of postoperative delirium was approximately 14% lower in the light anesthesia group compared to the deep anesthesia group ( P < 0.05). The QoR-15 scale scores on the first postoperative day were significantly higher in the light anesthesia group than in the deep anesthesia group ( P < 0.05). In contrast, the VAS scores over the three days following surgery were significantly higher in the deep anesthesia group than in the light anesthesia group ( P < 0.05). Conclusion The elderly pre-frail patients under light anesthesia (with high CSI score) may have lower incidence of postoperative delirium and better outcome. Trial registration: ChiCTR2400083016, Date of registration: 15/04/2025. anesthesia electroencephalography postoperative delirium elderly Pre-frailty Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Postoperative delirium is an acute central nervous system syndrome characterized by attention deficits, altered levels of consciousness, and sudden changes in cognitive function. It leads to prolonged hospital stay and delayed functional recovery [ 1 , 2 ]. The incidence of postoperative delirium varies widely, and was reported to be 10–50% with the highest rates occurring in older patients undergoing cardiac and major noncardiac surgery [ 3 ]. The development of delirium usually results from the interaction of multiple risk factors. Age is a significant risk factor for postoperative delirium [ 4 ]. Frailty, a common syndrome among the elderly, is characterized by a severe decline in function and heightened vulnerability to both external and internal stressors. This condition is associated with a high risk of adverse clinical outcomes, including mortality, fractures, decreased quality of life, and rehospitalization [ 5 , 6 ]. Pre-frailty is an early and reversible risk-state, as a condition preceding frailty, or as a condition that predisposes older adults to frailty[ 7 – 9 ]. In the elderly population, up to one-third were affected by pre-frailty, which is significantly associated with an increased risk of mortality. [ 10 , 11 ]. Patients undergoing cardiac surgery, pre-frailty was associated with 1.5-fold greater adjusted operative mortality[ 12 ]. In addition, an observational cohort study reported that pre-frailty and frailty were associated with incident delirium in older hospitalized patients (non-frail: 3.6% vs pre-frail: 20.9% vs frail: 29.3%) [ 13 ]. It is important to improve the outcome of pre-frail patients. There has been a substantial amount of research explored how to improve outcomes for frail patients [ 14 – 16 ]. However, few studies focusing on pre-frail patients whose postoperative recovery is often overlooked due to their relatively better physical condition compared to frail patients. Therefore, this study focused on pre-frail patients as the research subjects. Researches has shown that monitoring anesthetic depth may reduce postoperative delirium [ 17 , 18 ], but the effects of varying anesthetic depths as reflected by processed electroencephalogram monitors on this condition remain controversial. A systematic review reported that low BIS versus high BIS, the incidence of POD at 1 day was similar [ 19 ]. However, some studies have found that deep or light anesthesia can reduce the incidence of postoperative delirium or postoperative cognitive dysfunction [ 20 , 21 ]. Numerous instruments were utilized to monitor anesthetic depth, with the bispectral index (BIS) being the most widely used [ 22 , 23 ]. Compared to BIS, the Cerebral State Index (CSI) can also provide an accurate measurement of anesthetic depth, demonstrating greater sensitivity and is less prone to electrical interference [ 24 , 25 ]. Current studies about POD predominantly focused on orthopedic and cardiac surgeries, with relatively few investigating urological and general surgeries [ 4 ]. Therefore, this trial aimed to explore the influence of different CSI scores on postoperative delirium in elderly patients at pre-frail stage undergoing abdominal surgery. Material and Methods Study participants and ethical approval This prospective, double-blind, randomized, parallel-group study recruited elderly pre-frail patients undergoing general anesthesia for abdominal surgery at the Affiliated Hospital of North Sichuan Medical College from April to August 2024. Ethical approval (No. 2024ER194-1) was granted by the Medical Ethics Committee of Affiliated Hospital of North Sichuan Medical College in April 2024. All patients provided written informed consent prior to enrollment, and all procedures were conducted in accordance with the Helsinki Declaration. The trial has been registered at the China Clinical Trials Registry (ChiCTR2400083016). The inclusion criteria for the study were as follows: age over 65 years; American Society of Anesthesiologists (ASA) physical status classification II to III; absence of preoperative delirium as determined by the 3-Minute Diagnostic Confusion Assessment Method (3D-CAM) scale; Mini-Mental State Examination (MMSE) score of 15 or higher; a 5-Item Modified Frailty Index (mFI-5) score 1 or 2. The exclusion criteria were as follows: a history of neurological or psychiatric disorders; long-term use of sedative hypnotics or antipsychotics; severe dysfunction of vital organs, including the heart, lungs, liver, or kidneys. Patients were assigned to either deep anesthesia (DA) group or light anesthesia (LA) group according to a computer-generated randomization sequence. The anesthesia depth of LA group was maintained a CSI value between 50–59, while the anesthesia depth of DA group was maintained a CSI value between 40–49. Both patients and surgeons were blinded to the group assignments. Additionally, researcher responsible for postoperative data collection and outcome assessments was blinded to patient data. Anesthetic procedures and interventions Upon entering the operation room, patients were routinely monitored, administered oxygen with a mask, and intravenous access was established. After degreasing and drying the forehead with 75% ethanol, the CSI electrode was applied to the left side of the forehead and data were recorded once the values stabilized. Anesthesia induction strategy included propofol (1 mg/kg), sufentanil (0.3–0.5 µg/kg), cisatracurium (0.15 mg/kg), and etomidate (0.3 mg/kg). Endotracheal intubation was performed three minutes after induction. Mechanical ventilation was conducted using a volume-controlled mode, maintaining end-tidal carbon dioxide levels between 35 and 45 mmHg. All surgeries were laparoscopic, with the intraperitoneal pressure maintained at 12 mmHg. The anesthesia maintenance was based on the anesthesiologist's preference, choosing either sevoflurane or propofol. During the procedure, remifentanil was continuously infused, and cisatracurium was intermittently bolused. Anesthetic depth was regulated intraoperatively with maintenance drugs according to targeted CSI values. During surgery, adequate oxygenation and hemodynamic stability were ensured. Hypotension, defined as a systolic blood pressure below 80% of baseline, was treated with an intravenous injection of 6 mg ephedrine, while hypertension, defined as a systolic pressure above 120% of baseline, was managed with 15 mg of intravenous urapidil. Atropine or esmolol was administered to maintain an intraoperative heart rate between 50 and 100 beats per minute. Care was taken to maintain body warmth, perform timely blood gas analyses, and ensure stability of acid-base balance and the internal environment. Within 48 hours post-surgery, patients received a 150 mL saline solution containing 150 µg of sufentanil, 8 mg of butorphanol, and 5 mg of tropisetron via patient-controlled intravenous analgesia. The infusion rate was set at 2.5 ml/h, with a lockout period of 15 minutes and a bolus dose of 1.0 ml. Data collection Delirium was assessed daily (from 9 am to 11 am) during postoperative day 1 to day 3 using the 3D-CAM. Pain was assessed using the VAS (0 = no pain, 10 = worst possible pain) for the first three days postoperatively. Postoperative nausea and vomiting, cardiovascular events, ICU admissions, and mortality were also recorded. The quality of recovery on the first postoperative day was evaluated using the 15-item quality of recovery (QoR-15) scale. Other data were collected for all participants including age, sex, Body Mass Index (BMI), educational level, MMSE scores, the modified five-item frailty index, comorbidities, and surgery-related data such as duration of anesthesia, surgery time, volume of fluids and transfusions, dose of intravenous anesthetics, and use of vasoactive drugs. The mean arterial pressure and heart rate were recorded after entering the room (T1), one minute before induction (T2), one minute after induction (T3), one minute before intubation (T4), one minute after intubation (T5), and 0.5h (T6), 1h (T7), 1.5h (T8), 2h (T9) after the start of the surgery, and upon leaving the operating room (T10). Study endpoints The primary endpoint was the assessment of the incidence of delirium within three days post-surgery as determined by the 3D-CAM. Secondary endpoints included the VAS scores, nausea, the number of presses on the pain pump and vomiting within three days post-surgery, and the quality of recovery score on the first postoperative day as determined by the QoR-15 scale. Sample size calculation Based on pilot test results, the incidence of postoperative delirium (POD) was 33.3% in the deep anesthesia group and 12% in the light anesthesia group. Using a significance level of α = 0.05 (two-sided) and a power of (1-β) = 0.8, sample size estimation was performed using PASS 15.0 software. Accounting for a 20% attrition rate, 75 patients per group were required, totaling 150 patients across both groups. Statistical analysis Using a significance level of α = 0.05 (two-sided) and a power of Statistical analysis of all experimental data was conducted using SPSS 26 software. A normality test was performed on quantitative data, which are expressed as mean ± standard deviation (SD). The light anesthesia group and deep anesthesia group were compared using the independent-sample t-test, Fisher exact test, or Mann-Whitney U test, as appropriate. Categorical variables were compared using chi-square (χ²) tests or Fisher exact tests, as applicable. A P -value of < 0.05 was considered statistically significant. Results Participant characteristics and study groups The study flowchart is shown in Fig. 1 . Of the 168 patients screened for eligibility, 18 were excluded (1 met the exclusion criteria, and 17 declined to participate). In the light anesthesia group, 3 patients refused postoperative follow-up, and 1 patient received a nerve block postoperatively. In the deep anesthesia group, 4 refused postoperative follow-up, and 1 was admitted to the ICU postoperatively. After excluding 9 patients in two groups, 141 patients were enrolled for analysis. The demographic and clinical characteristics of the patients included in the analysis are presented in Table 1 . No significant differences were observed between the two groups regarding age, sex ratio, Mini-Mental State Examination (MMSE) scores, education level, Body Mass Index (BMI), type of surgery, frailty index, or comorbidities (Table 1 ) ( P > 0.05). Table 1 Demographic and clinical characteristics of the patients in the two groups LA group ( n = 71) DA group ( n = 70) P value Age (yr) 71 (67,76) 70.50 (68,75) 0.85 Sex Male Female 43 (60.56) 28 (39.44) 45 (64.29) 25 (35.71) 0.65 BMI (kg/㎡) 22.77 ± 3.39 22.84 ± 3.28 0.90 ASA Ⅱ 13 (18.31) 11 (15.71) 0.68 Ⅲ 58 (81.69) 59 (84.29) MMSE 25 (21,26) 26 (22.75,27) 0.12 Educational time (yr) 6 (3,7) 6 (4,9) 0.07 Type of surgery 0.20 Stomach 26 (36.62) 16 (22.86) Colon 17 (23.94) 20 (28.57) Rectum 28 (39.44) 34 (48.57) mFI-5 0.48 1 60 (84.51) 62 (88.57) 2 11 (15.49) 8 (11.43) Complication Hypertension 40 (56.3) 35 (50) 0.45 Diabetes 19 (26.8) 20 (28.6) 0.81 Non-independent functional state 10 (14.1) 8 (11.4) 0.64 COPD 13 (18.3) 15 (21.4) 0.64 Congestive heart failure (Within a month) 0 0 Notes: Data are mean ± standard deviation (SD), n (%), or median (P 25 ,P 75 ). CSI, Cerebral State Index; LA group, the group underwent adjustment of anesthesia to maintain a CSI value between 50–59; DA group, the group underwent adjustment of anesthesia to maintain a CSI value between 40–49; BMI, Body Mass Index; MMSE, Mini-Mental State Examination; ASA, American Society of Anesthesiology classification; mFI-5, 5-Item Modified Frailty Index; COPD, Chronic obstructive pulmonary disease. Table 2 Intraoperative characteristics LA group ( n = 71) DA group ( n = 70) P value Sedatives used for anesthesia maintenance 0.80 Propofol 38 (53.52) 36 (51.43) Sevoflurane 33 (46.48) 34 (48.57) Duration of surgery (min) 195 (150,226) 188.50 (155,250.25) 0.48 Duration of anesthesia (min) 225 (183,270) 221.50 (183.75,295) 0.66 Cisatracurium (mg) 17 (14,20) 16.5 (14,20) 0.78 Remifentanil (mg) 1.20 (0.90,1.50) 1 (0.69,1.30) ⁎ 0.02 Sevoflurane(ml) 38 ± 10 60 ± 22 ⁎ < 0.001 Propofol (mg) 950 (680,1250) 1200 (913,1588) ⁎ 0.002 The number of vasoactive drugs administered 25 (35.21) 33 (47.14) 0.15 Atropine 16 (22.54) 13 (18.57) 0.56 Ephedrine 13 (18.31) 19 (27.14) 0.21 Ebrantil Blood loss volume (ml) 9 (12.68) 50 (20,80) 8 (11.43) 50 (20,100) 0.82 0.59 Crystalloid solution (ml) 1600 (1200,1900) 1600 (1237.50,2000) 0.63 Colloidal solution (ml) 500 (500,500) 500 (500,500) 0.65 Blood transfusion (ml) 0 0 Urine volume (ml) 300 (200,500) 300 (300,612.50) 0.64 Notes: Data are mean ± standard deviation (SD), n (%), or median (P 25 ,P 75 ). CSI, Cerebral State Index (CSI); LA group, the group underwent adjustment of anesthesia to maintain a CSI value between 50–59; DA group, the group underwent adjustment of anesthesia to maintain a CSI value between 40–49; TIVA, total intravenous anesthesia; MAP, Mean arterial pressure; HR, Heart rate. ⁎ The dosage of anesthesia in DA group was significantly higher than that in LA group No significant differences were observed between the two groups regarding the proportion of different sedatives used for anesthesia maintenance, operation time, anesthesia time, intraoperative fluid intake, and urine output ( P > 0.05) (Table 2 ). Regarding the total dose of sedatives used for anesthesia maintenance, propofol and sevoflurane administered were significantly lower in the light anesthesia group compared to the deep anesthesia group ( P < 0.01) (Table 2 ). In contrast, remifentanil usage was significantly higher in the light anesthesia group ( P 0.05) (Table 2 ). The MAP in the deep anesthesia group was lower than in the light anesthesia group from T6 to T10, with statistical significance was found at T6, T7, and T9 ( P < 0.05) (Fig. 2 ). As shown in Fig. 3 , there was no statistically significant difference in heart rates between the two groups at each time point. The use of vasoactive drugs was 8% lower in the light anesthesia group compared to the deep anesthesia group, but the overall use of vasoactive drugs and the rates of usage for different types of vasoactive drugs did not differ significantly between the groups ( P > 0.05) (Table 2 ). Compared to the deep anesthesia group, the incidence of postoperative delirium was significantly lower in the light anesthesia group ( P < 0.05) (Table 3 ), showing a reduction of approximately 14%, mainly reflected on the first day after surgery. ( P < 0.05) (Fig. 4 ). Table 3 Postoperative primary and secondary outcome data of the two groups LA group ( n = 71) DA group ( n = 70) P value Primary outcome Number of POD 13 (18.3) 23 (32.9) ⁎ 0.048 Secondary outcomes QoR-15 97.41 ± 8.79 92.9 ± 11.8 ⁎ 0.011 Duration of hospital stay(days) 14(12,16) 15(12,18) 0.12 VAS Day 1 3.58 ± 1.19 4.09 ± 1.28 ⁎ 0.016 Day 2 2.61 ± 1.15 3.09 ± 1.2 ⁎ 0.017 Day 3 1.94 ± 0.83 2.4 ± 1.18 0.09 Nausea and vomiting 13(18.3) 12(17.1) 0.86 The number of presses on the pain pump 0(0,1) 1(0,2) ⁎ 0.025 Notes: Data are mean ± standard deviation (SD), n (%), or median (P 25 ,P 75 ). CSI, Cerebral State Index (CSI); LA group, the group underwent adjustment of anesthesia to maintain a CSI value between 50–59; DA group, the group underwent adjustment of anesthesia to maintain a CSI value between 40–49; POD, Postoperative delirium; QoR-15, the 15-item quality of recovery scale; VAS, Visual Analogue Scale. ⁎ VAS score on Day 1 and Day 2, Number of POD and the number of presses on the pain pump were significantly higher in DA group compared to LA group; QoR-15 score in DA group was significantly lower than LA group. The QoR-15 score was significantly higher in the light anesthesia group compared to the deep anesthesia group ( P 0.05) (Table 3 ). From the first to the third day after surgery, VAS scores and the number of presses on the pain pump were significantly lower in the light anesthesia group compared to the deep anesthesia group ( P 0.05) (Table 3 ). Discussion In this randomized controlled trial of elderly patients at pre-frail stage, the overall postoperative delirium incidence was 25.5%. Incidence were 32.9% in the deep anesthesia group and 18.3% in the light anesthesia group. The delirium incidence was significantly reduced in the light anesthesia group compared to the deep anesthesia group, with a reduction of approximately 14%. A study involving 150 non-cardiac surgeries reported postoperative delirium incidence of 39.3%, 29.8%, and 12.7% for frail, pre-frail, and non-frail patients, respectively [ 26 ]. The delirium incidence in pre-frail patients from that study is similar to the overall postoperative delirium incidence of 25.5% for pre-frail patients in this study. A prospective controlled study using bispectral index monitoring during colon cancer surgery in elderly patients found a delirium incidence of 17.5% in the BIS group [ 27 ]. This incidence is lower than the overall postoperative delirium incidence in this study, which may be attributed to the focus on pre-frail elderly patients. Frailty is a prevalent syndrome in the elderly, characterized by heightened vulnerability to both external and internal stressors, which increases the risk of adverse clinical outcomes across various settings [ 5 , 6 ]. Pre-frailty is a multi-dimensional concept, an early and reversible risk-state before frailty that can lead to negative healthcare outcomes [ 9 ]. Previous studies assessing the impact of anesthetic depth on postoperative delirium in elderly patients have seldom stratified by frailty status [ 17 , 21 , 27 ]. Additionally, while various preoperative frailty scoring scales are used in studies of postoperative delirium, their application has been inconsistent [ 28 – 30 ]. This study employs the mFI-5 scoring scale, a straightforward and precise tool for identifying frail or pre-frail individuals. It offers an objective method for evaluating frailty status and assessing the risk of complications in surgical patients [ 31 , 32 ], and provides valuable data on the incidence of postoperative delirium in pre-frail elderly patients undergoing abdominal surgery. Inflammatory marker levels in pre-frail patients are higher compared to those in healthy individuals, serum CRP and IL-6 are significantly elevated in pre-frail people [ 33 ], which may be the cause of postoperative delirium in pre-frail patients [ 34 – 36 ]. A study examining the impact of sedation depth on postoperative delirium following hip fracture repair in elderly patients found that the light sedation group had a lower incidence of postoperative delirium compared to the deep sedation group among patients with fewer complications [ 37 ]. In this study, the light anesthesia group had a lower rate of postoperative delirium compared to the deep anesthesia group, which is consistent with the study's findings mentioned above. Clinically, monitoring anesthetic depth can reduce the use of general anesthetics and mitigate the risk of adverse events [ 18 , 21 , 38 ]. Using processed EEG monitoring during anesthesia allows the anesthesiologist to reduce the amount of anesthetic administered, leading to a "lighter" level of anesthesia, as indicated by continuous processed EEG numbers such as BIS. This interpretation suggests that the anesthetic itself may be harmful to the brain, and thus reducing the dosage may decrease the incidence of postoperative delirium [ 39 , 40 ]. In this study, the doses of sevoflurane and propofol were significantly lower in the light anesthesia group compared to the deep anesthesia group, which may contribute to the reduced incidence of postoperative delirium. However, the hypothesis that the anesthetic dose directly causes acute brain dysfunction and leads to subsequent delirium in older patients has not been confirmed, and Taylor et al . found that sevoflurane dose was not associated with the severity and incidence of delirium [ 41 ]. A study has found that patients with electroencephalogram suppression at lower volatile anesthetic concentrations have an increased incidence of postoperative delirium. Such patients appear to exhibit a phenotype of anesthetic sensitivity, which might predispose them to adverse cognitive outcomes [ 42 ]. Therefore, the depth of anesthesia may simply be a marker for patient’s baseline brain vulnerability to the effects of anesthetics. The differentiation between direct effects of anesthetic effects on the brain versus patients’ baseline vulnerability is critical to understanding the relationship between delirium and the role of the use of processed electroencephalogram-guided anesthesia [ 43 ]. Currently, there was no definitive conclusion regarding the impact of propofol compared to sevoflurane on the incidence of postoperative delirium [ 44 , 45 ]. This trial used two anesthetic maintenance protocols, but there was no statistical difference in the proportions of these protocols between the two groups. Moreover, the use of two different anesthetic maintenance protocols better reflects the diversity of anesthetic practices in real clinical settings, providing a postoperative delirium incidence rate that more accurately aligns with clinical reality. In this study, the MAP in the DA group was lower than in the LA group from T6 to T10, with statistical significance was found at T6, T7, and T9. A retrospective multicenter cohort study found that in patients undergoing noncardiac surgery, a MAP < 55 mmHg was associated with a duration-dependent increase in odds of postoperative delirium [ 46 ]. Another study reported that intraoperative hypotension (MAP ≤ 65 mmHg) for ≥ 5 mins was associated with an increased incidence of POD after thoracic and orthopedic surgery in elderly [ 47 ]. In this trial, only a few time points showed differences in blood pressure between two groups, all of which were within the normal range and had a short duration. Moreover, a recent study found that intraoperative hypotension is not associated with postoperative delirium in elderly patients having elective noncardiac surgery [ 48 ]. Based on the existing studies, we believe that the hypotension in this study did not have a direct impact on the outcomes. Numerous instruments are employed to monitor anesthetic depth, with bispectral index (BIS) being the most prevalent [ 22 , 23 ]. An ideal anesthetic depth monitoring device should exhibit characteristics such as accuracy, specificity, sensitivity, stability, and robust resistance to interference. The CSI method for monitoring anesthetic depth operates by measuring EEG activity 2000 times per second. Sub-parameters of the EEG signals are processed by a computer-adaptive neuro-fuzzy inference system, which computes the CSI and displays it as a value between 0 and 100. Higher values indicate greater consciousness, while lower values suggest increased cortical suppression. The absolute values and consistency of the CSI are comparable to those of the BIS. Additionally, the CSI demonstrates greater sensitivity and is less prone to electrical interference [ 25 ]. CSI and BIS show similar variations across different sedation levels; however, CSI is superior in predicting the clinical outcomes of LVC (loss of verbal contact) and LOR (loss of responsiveness) [ 49 ]. Compared to BIS, CSI also offers a precise measurement of anesthetic depth [ 24 ]. This study utilizes CSI for monitoring anesthetic depth. Besides reflecting the depth index, the device also provides information on the burst suppression ratio, signal quality, and electromyographic activity. This enhances signal accuracy, enables timely detection and correction of transmission faults, and indirectly indicates excessive anesthesia and neuromuscular blockade, thus offering improved insight into intraoperative anesthetic management. The mechanism of delirium involves inflammatory responses [ 50 ], with surgical stress exacerbating inflammation [ 51 ]. Adequate intraoperative analgesia is crucial for reducing surgical stress. Since this study did not monitor pain-related indices, within the set anesthetic depth range, with vital sign fluctuations not exceeding 20%, researchers adjusted the amount of analgesic medication based on changes in patient vital signs. In this study, the light anesthesia group received significantly more remifentanil than the deep anesthesia group, which may have reduced the risk of inadequate intraoperative analgesia. Conversely, the deep anesthesia group exhibited less blood pressure variability, potentially masking signs of insufficient analgesia and leading to increased production of inflammatory mediators during surgery. This may also explain why the postoperative pain scores and the number of presses on the pain pump were higher in the deep anesthesia group compared to the light anesthesia group, with postoperative pain contributing to a higher incidence of delirium. Although the study observed variations in hospital stay durations between the two groups, these differences were not statistically significant. The group receiving light anesthesia demonstrated better postoperative recovery quality compared to the deep anesthesia group, yet this difference was not clinically meaningful. This discrepancy may be attributed to factors such as the recovery of gastrointestinal function influencing the overall quality of postoperative recovery. Limitations and strengths First, this study did not collect perioperative inflammatory markers due to considerations regarding patient costs, it was not possible to further explore the impact of changes in inflammatory factors on the incidence of postoperative delirium in patients at the pre-frailty stage. Second, due to the differences in patients' education levels, this study set the inclusion criterion as MMSE score of 15 or higher. This may lead to a higher incidence of postoperative delirium. However, there was no statistically significant difference in MMSE scores between the two groups, so the inclusion criterion did not affect the result that light anesthesia may reduce the incidence of postoperative delirium in patients at the pre-frailty stage. Conclusions This randomized controlled trial employed two anesthesia protocols that closer to clinical practice. Moreover, it used a highly reliable frailty scale to screen pre-frail elderly patients and CSI that demonstrates greater sensitivity and is less prone to electrical interference than BIS. This study provided clinical data on the incidence of postoperative delirium following abdominal surgery in elderly patients at pre-frail stage and offered insights into strategies for reducing postoperative delirium incidence in this group. In conclusion, the elderly pre-frail patients under light anesthesia (with high CSI score) may have lower incidence of postoperative delirium and better outcome. Abbreviations CSI cerebral state index BIS bispectral index mFI-5 a 5-Item Modified Frailty Index scale LA light anesthesia DA deep anesthesia VAS visual analog scale QoR-15 the 15-item quality of recovery scale BMI Body Mass Index MMSE Mini-Mental State Examination ASA American Society of Anesthesiology classification COPD Chronic obstructive pulmonary disease TIVA total intravenous anesthesia MAP Mean arterial pressure HR Heart rate POD Postoperative delirium Declarations Ethics approval and consent to participate Ethical approval (No. 2024ER194-1) was granted by the Medical Ethics Committee of Affiliated Hospital of North Sichuan Medical College in April 2024. All patients provided written informed consent prior to enrollment, and all procedures were conducted in accordance with the Helsinki Declaration. Consent for publication Informed consent for information collection for research was obtained from all participants and the hospital review board provided us with consent for publication. Availability of data and materials The datasets used during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare no competing interests. Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Authors' contributions All authors contributed to conceptualization and methodology. The first draft of the manuscript was written by RMC. Formal analysis was performed by HQM and SYJ. Data curation and investigation were performed by PFH. Project administration and supervision was performed by WXL. All authors commented on previous versions of the manuscript. The review and editing was performed by JYL. All authors read and approved the final manuscript. 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A systematic review with meta-analysis . PloS One 2020, 15 (2):e0229018. Farag E, Chelune GJ, Schubert A, Mascha EJ: Is depth of anesthesia, as assessed by the Bispectral Index, related to postoperative cognitive dysfunction and recovery? Anesthesia and Analgesia 2006, 103 (3):633-640. Evered LA, Chan MTV, Han R, Chu MHM, Cheng BP, Scott DA, Pryor KO, Sessler DI, Veselis R, Frampton C et al : Anaesthetic depth and delirium after major surgery: a randomised clinical trial . Br J Anaesth 2021, 127 (5):704-712. Musizza B, Ribaric S: Monitoring the depth of anaesthesia . Sensors (Basel) 2010, 10 (12):10896-10935. Laferrière-Langlois P, Morisson L, Jeffries S, Duclos C, Espitalier F, Richebé P: Depth of Anesthesia and Nociception Monitoring: Current State and Vision For 2050 . Anesthesia and Analgesia 2024, 138 (2):295-307. Herzog M, Rudzki M, Plößl S, Plontke S, Kellner P: Depth of sedation during drug induced sedation endoscopy monitored by BiSpectral Index® and Cerebral State Index® . Sleep Breath 2021, 25 (2):1029-1035. Nishiyama T, Komatsu K: Cerebral state index versus bispectral index during propofol-fentanyl-nitrous oxide anesthesia . J Anesth 2010, 24 (3):380-385. Mahanna-Gabrielli E, Zhang K, Sieber FE, Lin HM, Liu X, Sewell M, Deiner SG, Boockvar KS: Frailty Is Associated With Postoperative Delirium But Not With Postoperative Cognitive Decline in Older Noncardiac Surgery Patients . Anesthesia and Analgesia 2020, 130 (6):1516-1523. Zhou Y, Li Y, Wang K: Bispectral Index Monitoring During Anesthesia Promotes Early Postoperative Recovery of Cognitive Function and Reduces Acute Delirium in Elderly Patients with Colon Carcinoma: A Prospective Controlled Study using the Attention Network Test . Med Sci Monit 2018, 24 :7785-7793. Eide LSP, Ranhoff AH, Fridlund B, Haaverstad R, Hufthammer KO, Kuiper KKJ, Nordrehaug JE, Norekvål TM: Comparison of frequency, risk factors, and time course of postoperative delirium in octogenarians after transcatheter aortic valve implantation versus surgical aortic valve replacement . The American Journal of Cardiology 2015, 115 (6):802-809. Jung P, Pereira MA, Hiebert B, Song X, Rockwood K, Tangri N, Arora RC: The impact of frailty on postoperative delirium in cardiac surgery patients . J Thorac Cardiovasc Surg 2015, 149 (3). Leung JM, Tsai TL, Sands LP: Brief report: preoperative frailty in older surgical patients is associated with early postoperative delirium . Anesthesia and Analgesia 2011, 112 (5):1199-1201. Li B, Meng X, Zhang X, Hai Y: Frailty as a risk factor for postoperative complications in adult patients with degenerative scoliosis administered posterior single approach, long-segment corrective surgery: a retrospective cohort study . BMC Musculoskelet Disord 2021, 22 (1):333. Yagi M, Michikawa T, Hosogane N, Fujita N, Okada E, Suzuki S, Tsuji O, Nagoshi N, Asazuma T, Tsuji T et al : The 5-Item Modified Frailty Index Is Predictive of Severe Adverse Events in Patients Undergoing Surgery for Adult Spinal Deformity . Spine (Phila Pa 1976) 2019, 44 (18):E1083-E1091. Soysal P, Stubbs B, Lucato P, Luchini C, Solmi M, Peluso R, Sergi G, Isik AT, Manzato E, Maggi S et al : Inflammation and frailty in the elderly: A systematic review and meta-analysis . Ageing Res Rev 2016, 31 :1-8. de Rooij SE, van Munster BC, Korevaar JC, Levi M: Cytokines and acute phase response in delirium . J Psychosom Res 2007, 62 (5):521-525. van Munster BC, Korevaar JC, Zwinderman AH, Levi M, Wiersinga WJ, De Rooij SE: Time-course of cytokines during delirium in elderly patients with hip fractures . Journal of the American Geriatrics Society 2008, 56 (9):1704-1709. Yaffe K, Lindquist K, Penninx BW, Simonsick EM, Pahor M, Kritchevsky S, Launer L, Kuller L, Rubin S, Harris T: Inflammatory markers and cognition in well-functioning African-American and white elders . Neurology 2003, 61 (1):76-80. Sieber FE, Neufeld KJ, Gottschalk A, Bigelow GE, Oh ES, Rosenberg PB, Mears SC, Stewart KJ, Ouanes J-PP, Jaberi M et al : Effect of Depth of Sedation in Older Patients Undergoing Hip Fracture Repair on Postoperative Delirium: The STRIDE Randomized Clinical Trial . JAMA Surg 2018, 153 (11):987-995. Punjasawadwong Y, Chau-In W, Laopaiboon M, Punjasawadwong S, Pin-On P: Processed electroencephalogram and evoked potential techniques for amelioration of postoperative delirium and cognitive dysfunction following non-cardiac and non-neurosurgical procedures in adults . The Cochrane Database of Systematic Reviews 2018, 5 (5):CD011283. Fei X, Wang J-X, Wu Y, Dong N, Sheng Z-Y: Sevoflurane-induced cognitive decline in aged mice: Involvement of toll-like receptors 4 . Brain Res Bull 2020, 165 :23-29. Ebrahimi M, Dabbagh A, Madadi F: Propofol-induced hippocampal Neurotoxicity: A mitochondrial perspective . Brain Res 2024, 1831 :148841. Taylor J, Payne T, Casey C, Kunkel D, Parker M, Rivera C, Zetterberg H, Blennow K, Pearce RA, Lennertz RC et al : Sevoflurane dose and postoperative delirium: a prospective cohort analysis . Br J Anaesth 2023, 130 (2):e289-e297. Fritz BA, Kalarickal PL, Maybrier HR, Muench MR, Dearth D, Chen Y, Escallier KE, Ben Abdallah A, Lin N, Avidan MS: Intraoperative Electroencephalogram Suppression Predicts Postoperative Delirium . Anesthesia and Analgesia 2016, 122 (1):234-242. MacKenzie KK, Britt-Spells AM, Sands LP, Leung JM: Processed Electroencephalogram Monitoring and Postoperative Delirium: A Systematic Review and Meta-analysis . Anesthesiology 2018, 129 (3):417-427. Mei X, Zheng H-L, Li C, Ma X, Zheng H, Marcantonio E, Xie Z, Shen Y: The Effects of Propofol and Sevoflurane on Postoperative Delirium in Older Patients: A Randomized Clinical Trial Study . J Alzheimers Dis 2020, 76 (4):1627-1636. Cao S-J, Zhang Y, Zhang Y-X, Zhao W, Pan L-H, Sun X-D, Jia Z, Ouyang W, Ye Q-S, Zhang F-X et al : Delirium in older patients given propofol or sevoflurane anaesthesia for major cancer surgery: a multicentre randomised trial . Br J Anaesth 2023, 131 (2):253-265. Wachtendorf LJ, Azimaraghi O, Santer P, Linhardt FC, Blank M, Suleiman A, Ahn C, Low YH, Teja B, Kendale SM et al : Association Between Intraoperative Arterial Hypotension and Postoperative Delirium After Noncardiac Surgery: A Retrospective Multicenter Cohort Study . Anesthesia and Analgesia 2022, 134 (4):822-833. Duan W, Zhou C-M, Yang J-J, Zhang Y, Li Z-P, Ma D-Q, Yang J-J: A long duration of intraoperative hypotension is associated with postoperative delirium occurrence following thoracic and orthopedic surgery in elderly . Journal of Clinical Anesthesia 2023, 88 :111125. Zarour S, Weiss Y, Abu-Ghanim M, Iacubovici L, Shaylor R, Rosenberg O, Matot I, Cohen B: Association between Intraoperative Hypotension and Postoperative Delirium: A Retrospective Cohort Analysis . Anesthesiology 2024, 141 (4):707-718. Zhong T, Guo QL, Pang YD, Peng LF, Li CL: Comparative evaluation of the cerebral state index and the bispectral index during target-controlled infusion of propofol . Br J Anaesth 2005, 95 (6):798-802. Brattinga B, Plas M, Spikman JM, Rutgers A, de Haan JJ, Absalom AR, van der Wal-Huisman H, de Bock GH, van Leeuwen BL: The association between the inflammatory response following surgery and post-operative delirium in older oncological patients: a prospective cohort study . Age Ageing 2022, 51 (2). Alam A, Hana Z, Jin Z, Suen KC, Ma D: Surgery, neuroinflammation and cognitive impairment . EBioMedicine 2018, 37 :547-556. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 28 Jul, 2025 Read the published version in Perioperative Medicine → Version 1 posted Editorial decision: Revision requested 28 Apr, 2025 Reviews received at journal 19 Apr, 2025 Reviews received at journal 17 Apr, 2025 Reviewers agreed at journal 11 Apr, 2025 Reviewers agreed at journal 07 Apr, 2025 Reviewers agreed at journal 05 Apr, 2025 Reviewers agreed at journal 16 Mar, 2025 Reviews received at journal 15 Mar, 2025 Reviewers agreed at journal 15 Mar, 2025 Reviewers invited by journal 14 Mar, 2025 Editor assigned by journal 10 Feb, 2025 Submission checks completed at journal 06 Feb, 2025 First submitted to journal 03 Feb, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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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-5950908","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":412002371,"identity":"62d55680-27bb-435b-83a3-aea9560816f9","order_by":0,"name":"Rongman Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACfvnzHw4k8Ngw87M3EKlFcgaD4YEHMmnskj0HiNRiMIPB+OADm8P8BjcSiNUi3ZBwICEnTZrh5uONNxhqbKIJajGXOXDgQMIZG2PG2WnFFgzH0nIbCGmxbEhsOJDYk5bMLJ1jJsHYcJiwFoMDyQwHEv8drm+TPEOslhtpDMBAPszMI8FDpBbJnjMgLWnMEjxAvyQQ4xd+9h7mjz+AUWl//PDGGx9qbAhrQXGkRAIpyiFaSNUxCkbBKBgFIwMAADzHQx9L+29EAAAAAElFTkSuQmCC","orcid":"","institution":"Affiliated Hospital of North Sichuan Medical College","correspondingAuthor":true,"prefix":"","firstName":"Rongman","middleName":"","lastName":"Chen","suffix":""},{"id":412002372,"identity":"ae58b78e-464d-48c9-9a36-ca3cc92414f9","order_by":1,"name":"Pengfei Hou","email":"","orcid":"","institution":"Affiliated Hospital of North Sichuan Medical College","correspondingAuthor":false,"prefix":"","firstName":"Pengfei","middleName":"","lastName":"Hou","suffix":""},{"id":412002373,"identity":"e98dc689-b83a-4c1a-b555-b09c2266be60","order_by":2,"name":"Wanxin Liu","email":"","orcid":"","institution":"Affiliated Hospital of North Sichuan Medical College","correspondingAuthor":false,"prefix":"","firstName":"Wanxin","middleName":"","lastName":"Liu","suffix":""},{"id":412002374,"identity":"a81af014-82bd-40d0-b576-d4370919776c","order_by":3,"name":"Haiqi Mi","email":"","orcid":"","institution":"Affiliated Hospital of North Sichuan Medical College","correspondingAuthor":false,"prefix":"","firstName":"Haiqi","middleName":"","lastName":"Mi","suffix":""},{"id":412002375,"identity":"27b51894-d4af-46cb-b797-62713e26c2ca","order_by":4,"name":"Shuaiying Jia","email":"","orcid":"","institution":"Affiliated Hospital of North Sichuan Medical College","correspondingAuthor":false,"prefix":"","firstName":"Shuaiying","middleName":"","lastName":"Jia","suffix":""},{"id":412002376,"identity":"6f9c54f2-c549-4e72-8977-9be93ffbfe1a","order_by":5,"name":"Jingyan Lin","email":"","orcid":"","institution":"Affiliated Hospital of North Sichuan Medical College","correspondingAuthor":false,"prefix":"","firstName":"Jingyan","middleName":"","lastName":"Lin","suffix":""}],"badges":[],"createdAt":"2025-02-03 12:08:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5950908/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5950908/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s13741-025-00561-5","type":"published","date":"2025-07-28T16:38:19+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":75997435,"identity":"e6fa1a8a-e5d0-40dd-ac39-ed97dbe4bb2d","added_by":"auto","created_at":"2025-02-11 10:03:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":150723,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of the study design. CSI, Cerebral State Index; LA group, the group underwent adjustment of anesthesia to maintain a CSI value between 50-59; DA group, the group underwent adjustment of anesthesia to maintain a CSI value between 40–49;\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5950908/v1/36ce1b0e947aa9274f1e2a83.png"},{"id":75997009,"identity":"f0feb935-27d4-4406-b06a-87b5f361bf45","added_by":"auto","created_at":"2025-02-11 09:55:50","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":102726,"visible":true,"origin":"","legend":"\u003cp\u003eMAP values from T1 to T10. T1, after entering the operating room; T2, one minute before induction; T3, one minute after induction; T4, one minute before intubation; T5, one minute after intubation; T6, 0.5h after the start of the surgery; T7, 1h after the start of the surgery; T8, 1.5h after the start of the surgery; T9, 2h after the start of the surgery; T10, leaving the operating room;CSI, Cerebral State Index (CSI); LA, the group underwent adjustment of anesthesia to maintain a CSI value between 50-59; DA, the group underwent adjustment of anesthesia to maintain a CSI value between 40–49; MAP, Mean arterial pressure. ⁎ indicates \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5950908/v1/c1bbc6e4046a83011c7e979c.png"},{"id":75997013,"identity":"c3e22b25-36e8-4b15-9c0f-b1d87d79b781","added_by":"auto","created_at":"2025-02-11 09:55:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":37019,"visible":true,"origin":"","legend":"\u003cp\u003eHR values from T1 to T10. T1, after entering the operating room; T2, one minute before induction; T3, one minute after induction; T4, one minute before intubation; T5, one minute after intubation; T6, 0.5h after the start of the surgery; T7, 1h after the start of the surgery; T8, 1.5h after the start of the surgery; T9, 2h after the start of the surgery; T10, leaving the operating room; CSI, Cerebral State Index (CSI); LA, the group underwent adjustment of anesthesia to maintain a CSI value between 50-59; DA, the group underwent adjustment of anesthesia to maintain a CSI value between 40–49; HR, Heart rate.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5950908/v1/f805be2104aa309cb165904c.png"},{"id":75997012,"identity":"9ed48757-4d7b-49d6-98c8-3cdb7c82451a","added_by":"auto","created_at":"2025-02-11 09:55:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":27059,"visible":true,"origin":"","legend":"\u003cp\u003eIncidence of postoperative delirium in both groups on each day. POD, Postoperative delirium; CSI, Cerebral State Index (CSI); LA, the group underwent adjustment of anesthesia to maintain a CSI value between 50-59; DA, the group underwent adjustment of anesthesia to maintain a CSI value between 40–49; ⁎indicates \u003cem\u003eP\u003c/em\u003e ＜0.05\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5950908/v1/14250dedb72f46a71f46b496.png"},{"id":88268476,"identity":"b17e72e2-31f4-4f56-b5b6-19062489abdb","added_by":"auto","created_at":"2025-08-04 16:52:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3578524,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5950908/v1/c5283447-c377-42a2-8f30-2efe34f8fcb8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eInfluence of different anesthetic depth on postoperative delirium in elderly pre-frail patients undergoing abdominal surgery\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePostoperative delirium is an acute central nervous system syndrome characterized by attention deficits, altered levels of consciousness, and sudden changes in cognitive function. It leads to prolonged hospital stay and delayed functional recovery [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The incidence of postoperative delirium varies widely, and was reported to be 10\u0026ndash;50% with the highest rates occurring in older patients undergoing cardiac and major noncardiac surgery [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The development of delirium usually results from the interaction of multiple risk factors.\u003c/p\u003e \u003cp\u003eAge is a significant risk factor for postoperative delirium [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Frailty, a common syndrome among the elderly, is characterized by a severe decline in function and heightened vulnerability to both external and internal stressors. This condition is associated with a high risk of adverse clinical outcomes, including mortality, fractures, decreased quality of life, and rehospitalization [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Pre-frailty is an early and reversible risk-state, as a condition preceding frailty, or as a condition that predisposes older adults to frailty[\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In the elderly population, up to one-third were affected by pre-frailty, which is significantly associated with an increased risk of mortality. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Patients undergoing cardiac surgery, pre-frailty was associated with 1.5-fold greater adjusted operative mortality[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In addition, an observational cohort study reported that pre-frailty and frailty were associated with incident delirium in older hospitalized patients (non-frail: 3.6% vs pre-frail: 20.9% vs frail: 29.3%) [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. It is important to improve the outcome of pre-frail patients. There has been a substantial amount of research explored how to improve outcomes for frail patients [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. However, few studies focusing on pre-frail patients whose postoperative recovery is often overlooked due to their relatively better physical condition compared to frail patients. Therefore, this study focused on pre-frail patients as the research subjects.\u003c/p\u003e \u003cp\u003eResearches has shown that monitoring anesthetic depth may reduce postoperative delirium [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], but the effects of varying anesthetic depths as reflected by processed electroencephalogram monitors on this condition remain controversial. A systematic review reported that low BIS versus high BIS, the incidence of POD at 1 day was similar [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, some studies have found that deep or light anesthesia can reduce the incidence of postoperative delirium or postoperative cognitive dysfunction [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Numerous instruments were utilized to monitor anesthetic depth, with the bispectral index (BIS) being the most widely used [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Compared to BIS, the Cerebral State Index (CSI) can also provide an accurate measurement of anesthetic depth, demonstrating greater sensitivity and is less prone to electrical interference [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Current studies about POD predominantly focused on orthopedic and cardiac surgeries, with relatively few investigating urological and general surgeries [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTherefore, this trial aimed to explore the influence of different CSI scores on postoperative delirium in elderly patients at pre-frail stage undergoing abdominal surgery.\u003c/p\u003e"},{"header":"Material and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy participants and ethical approval\u003c/h2\u003e \u003cp\u003eThis prospective, double-blind, randomized, parallel-group study recruited elderly pre-frail patients undergoing general anesthesia for abdominal surgery at the Affiliated Hospital of North Sichuan Medical College from April to August 2024.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eEthical approval\u003c/strong\u003e \u003cp\u003e(No. 2024ER194-1) was granted by the Medical Ethics Committee of Affiliated Hospital of North Sichuan Medical College in April 2024. All patients provided written informed consent prior to enrollment, and all procedures were conducted in accordance with the Helsinki Declaration. The trial has been registered at the China Clinical Trials Registry (ChiCTR2400083016).\u003c/p\u003e \u003c/p\u003e \u003cp\u003eThe inclusion criteria for the study were as follows: age over 65 years; American Society of Anesthesiologists (ASA) physical status classification II to III; absence of preoperative delirium as determined by the 3-Minute Diagnostic Confusion Assessment Method (3D-CAM) scale; Mini-Mental State Examination (MMSE) score of 15 or higher; a 5-Item Modified Frailty Index (mFI-5) score 1 or 2.\u003c/p\u003e \u003cp\u003eThe exclusion criteria were as follows: a history of neurological or psychiatric disorders; long-term use of sedative hypnotics or antipsychotics; severe dysfunction of vital organs, including the heart, lungs, liver, or kidneys.\u003c/p\u003e \u003cp\u003ePatients were assigned to either deep anesthesia (DA) group or light anesthesia (LA) group according to a computer-generated randomization sequence. The anesthesia depth of LA group was maintained a CSI value between 50\u0026ndash;59, while the anesthesia depth of DA group was maintained a CSI value between 40\u0026ndash;49. Both patients and surgeons were blinded to the group assignments. Additionally, researcher responsible for postoperative data collection and outcome assessments was blinded to patient data.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eAnesthetic procedures and interventions\u003c/h3\u003e\n\u003cp\u003eUpon entering the operation room, patients were routinely monitored, administered oxygen with a mask, and intravenous access was established. After degreasing and drying the forehead with 75% ethanol, the CSI electrode was applied to the left side of the forehead and data were recorded once the values stabilized. Anesthesia induction strategy included propofol (1 mg/kg), sufentanil (0.3\u0026ndash;0.5 \u0026micro;g/kg), cisatracurium (0.15 mg/kg), and etomidate (0.3 mg/kg). Endotracheal intubation was performed three minutes after induction. Mechanical ventilation was conducted using a volume-controlled mode, maintaining end-tidal carbon dioxide levels between 35 and 45 mmHg. All surgeries were laparoscopic, with the intraperitoneal pressure maintained at 12 mmHg. The anesthesia maintenance was based on the anesthesiologist's preference, choosing either sevoflurane or propofol. During the procedure, remifentanil was continuously infused, and cisatracurium was intermittently bolused. Anesthetic depth was regulated intraoperatively with maintenance drugs according to targeted CSI values.\u003c/p\u003e \u003cp\u003eDuring surgery, adequate oxygenation and hemodynamic stability were ensured. Hypotension, defined as a systolic blood pressure below 80% of baseline, was treated with an intravenous injection of 6 mg ephedrine, while hypertension, defined as a systolic pressure above 120% of baseline, was managed with 15 mg of intravenous urapidil. Atropine or esmolol was administered to maintain an intraoperative heart rate between 50 and 100 beats per minute. Care was taken to maintain body warmth, perform timely blood gas analyses, and ensure stability of acid-base balance and the internal environment. Within 48 hours post-surgery, patients received a 150 mL saline solution containing 150 \u0026micro;g of sufentanil, 8 mg of butorphanol, and 5 mg of tropisetron via patient-controlled intravenous analgesia. The infusion rate was set at 2.5 ml/h, with a lockout period of 15 minutes and a bolus dose of 1.0 ml.\u003c/p\u003e\n\u003ch3\u003eData collection\u003c/h3\u003e\n\u003cp\u003eDelirium was assessed daily (from 9 am to 11 am) during postoperative day 1 to day 3 using the 3D-CAM. Pain was assessed using the VAS (0\u0026thinsp;=\u0026thinsp;no pain, 10\u0026thinsp;=\u0026thinsp;worst possible pain) for the first three days postoperatively. Postoperative nausea and vomiting, cardiovascular events, ICU admissions, and mortality were also recorded. The quality of recovery on the first postoperative day was evaluated using the 15-item quality of recovery (QoR-15) scale. Other data were collected for all participants including age, sex, Body Mass Index (BMI), educational level, MMSE scores, the modified five-item frailty index, comorbidities, and surgery-related data such as duration of anesthesia, surgery time, volume of fluids and transfusions, dose of intravenous anesthetics, and use of vasoactive drugs. The mean arterial pressure and heart rate were recorded after entering the room (T1), one minute before induction (T2), one minute after induction (T3), one minute before intubation (T4), one minute after intubation (T5), and 0.5h (T6), 1h (T7), 1.5h (T8), 2h (T9) after the start of the surgery, and upon leaving the operating room (T10).\u003c/p\u003e\n\u003ch3\u003eStudy endpoints\u003c/h3\u003e\n\u003cp\u003eThe primary endpoint was the assessment of the incidence of delirium within three days post-surgery as determined by the 3D-CAM. Secondary endpoints included the VAS scores, nausea, the number of presses on the pain pump and vomiting within three days post-surgery, and the quality of recovery score on the first postoperative day as determined by the QoR-15 scale.\u003c/p\u003e\n\u003ch3\u003eSample size calculation\u003c/h3\u003e\n\u003cp\u003eBased on pilot test results, the incidence of postoperative delirium (POD) was 33.3% in the deep anesthesia group and 12% in the light anesthesia group. Using a significance level of α\u0026thinsp;=\u0026thinsp;0.05 (two-sided) and a power of (1-β)\u0026thinsp;=\u0026thinsp;0.8, sample size estimation was performed using PASS 15.0 software. Accounting for a 20% attrition rate, 75 patients per group were required, totaling 150 patients across both groups.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eUsing a significance level of α\u0026thinsp;=\u0026thinsp;0.05 (two-sided) and a power of Statistical analysis of all experimental data was conducted using SPSS 26 software. A normality test was performed on quantitative data, which are expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD). The light anesthesia group and deep anesthesia group were compared using the independent-sample t-test, Fisher exact test, or Mann-Whitney U test, as appropriate. Categorical variables were compared using chi-square (χ\u0026sup2;) tests or Fisher exact tests, as applicable. A \u003cem\u003eP\u003c/em\u003e -value of \u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003eParticipant characteristics and study groups\u003c/h2\u003e\n \u003cp\u003eThe study flowchart is shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. Of the 168 patients screened for eligibility, 18 were excluded (1 met the exclusion criteria, and 17 declined to participate). In the light anesthesia group, 3 patients refused postoperative follow-up, and 1 patient received a nerve block postoperatively. In the deep anesthesia group, 4 refused postoperative follow-up, and 1 was admitted to the ICU postoperatively. After excluding 9 patients in two groups, 141 patients were enrolled for analysis.\u003c/p\u003e\n \u003cp\u003eThe demographic and clinical characteristics of the patients included in the analysis are presented in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. No significant differences were observed between the two groups regarding age, sex ratio, Mini-Mental State Examination (MMSE) scores, education level, Body Mass Index (BMI), type of surgery, frailty index, or comorbidities (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDemographic and clinical characteristics of the patients in the two groups\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLA group (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;71)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDA group (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;70)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge (yr)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71 (67,76)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e70.50 (68,75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSex\u003c/p\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e43 (60.56)\u003c/p\u003e\n \u003cp\u003e28 (39.44)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e45 (64.29)\u003c/p\u003e\n \u003cp\u003e25 (35.71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBMI (kg/㎡)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.77\u0026thinsp;\u0026plusmn;\u0026thinsp;3.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.84\u0026thinsp;\u0026plusmn;\u0026thinsp;3.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.90\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eASA\u003c/p\u003e\n \u003cp\u003eⅡ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13 (18.31)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11 (15.71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.68\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eⅢ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e58 (81.69)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e59 (84.29)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMMSE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25 (21,26)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26 (22.75,27)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEducational time (yr)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6 (3,7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6 (4,9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eType of surgery\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomach\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26 (36.62)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16 (22.86)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eColon\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17 (23.94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20 (28.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRectum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28 (39.44)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34 (48.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emFI-5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.48\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e60 (84.51)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e62 (88.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11 (15.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8 (11.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eComplication\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHypertension\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e40 (56.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e35 (50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDiabetes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19 (26.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20 (28.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNon-independent functional state\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10 (14.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8 (11.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCOPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13 (18.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15 (21.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCongestive heart failure (Within a month)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003eNotes: Data are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD), n (%), or median (P\u003csub\u003e25\u003c/sub\u003e,P\u003csub\u003e75\u003c/sub\u003e). CSI, Cerebral State Index; LA group, the group underwent adjustment of anesthesia to maintain a CSI value between 50\u0026ndash;59; DA group, the group underwent adjustment of anesthesia to maintain a CSI value between 40\u0026ndash;49; BMI, Body Mass Index; MMSE, Mini-Mental State Examination; ASA, American Society of Anesthesiology classification; mFI-5, 5-Item Modified Frailty Index; COPD, Chronic obstructive pulmonary disease.\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eIntraoperative characteristics\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLA group (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;71)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDA group (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;70)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSedatives used for anesthesia maintenance\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePropofol\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38 (53.52)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e36 (51.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSevoflurane\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33 (46.48)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34 (48.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDuration of surgery (min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e195 (150,226)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e188.50 (155,250.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.48\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDuration of anesthesia (min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e225 (183,270)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e221.50 (183.75,295)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.66\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCisatracurium (mg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17 (14,20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.5 (14,20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRemifentanil (mg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.20 (0.90,1.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1 (0.69,1.30)\u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSevoflurane(ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38\u0026thinsp;\u0026plusmn;\u0026thinsp;10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e60\u0026thinsp;\u0026plusmn;\u0026thinsp;22\u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePropofol (mg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e950 (680,1250)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1200 (913,1588) \u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThe number of vasoactive drugs administered\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25 (35.21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33 (47.14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAtropine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16 (22.54)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13 (18.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEphedrine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13 (18.31)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19 (27.14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEbrantil\u003c/p\u003e\n \u003cp\u003eBlood loss volume (ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9 (12.68)\u003c/p\u003e\n \u003cp\u003e50 (20,80)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8 (11.43)\u003c/p\u003e\n \u003cp\u003e50 (20,100)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.82\u003c/p\u003e\n \u003cp\u003e0.59\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCrystalloid solution (ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1600 (1200,1900)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1600 (1237.50,2000)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eColloidal solution (ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e500 (500,500)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e500 (500,500)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBlood transfusion (ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUrine volume (ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e300 (200,500)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e300 (300,612.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003eNotes: Data are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD), n (%), or median (P\u003csub\u003e25\u003c/sub\u003e,P\u003csub\u003e75\u003c/sub\u003e). CSI, Cerebral State Index (CSI); LA group, the group underwent adjustment of anesthesia to maintain a CSI value between 50\u0026ndash;59; DA group, the group underwent adjustment of anesthesia to maintain a CSI value between 40\u0026ndash;49; TIVA, total intravenous anesthesia; MAP, Mean arterial pressure; HR, Heart rate. ⁎ The dosage of anesthesia in DA group was significantly higher than that in LA group\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003eNo significant differences were observed between the two groups regarding the proportion of different sedatives used for anesthesia maintenance, operation time, anesthesia time, intraoperative fluid intake, and urine output (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eRegarding the total dose of sedatives used for anesthesia maintenance, propofol and sevoflurane administered were significantly lower in the light anesthesia group compared to the deep anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). In contrast, remifentanil usage was significantly higher in the light anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e), and there was no significant difference in the use of muscle relaxant between the two groups (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe MAP in the deep anesthesia group was lower than in the light anesthesia group from T6 to T10, with statistical significance was found at T6, T7, and T9 (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). As shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, there was no statistically significant difference in heart rates between the two groups at each time point. The use of vasoactive drugs was 8% lower in the light anesthesia group compared to the deep anesthesia group, but the overall use of vasoactive drugs and the rates of usage for different types of vasoactive drugs did not differ significantly between the groups (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eCompared to the deep anesthesia group, the incidence of postoperative delirium was significantly lower in the light anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e), showing a reduction of approximately 14%, mainly reflected on the first day after surgery. (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePostoperative primary and secondary outcome data of the two groups\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLA group (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;71)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDA group (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;70)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePrimary outcome\u003c/p\u003e\n \u003cp\u003eNumber of POD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13 (18.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23 (32.9)\u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.048\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSecondary outcomes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQoR-15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e97.41\u0026thinsp;\u0026plusmn;\u0026thinsp;8.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e92.9\u0026thinsp;\u0026plusmn;\u0026thinsp;11.8\u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDuration of hospital stay(days)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14(12,16)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15(12,18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVAS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDay 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.58\u0026thinsp;\u0026plusmn;\u0026thinsp;1.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.09\u0026thinsp;\u0026plusmn;\u0026thinsp;1.28\u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.016\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDay 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.61\u0026thinsp;\u0026plusmn;\u0026thinsp;1.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.09\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2\u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.017\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDay 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNausea and vomiting\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13(18.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12(17.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThe number of presses on the pain pump\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0(0,1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1(0,2) \u003csup\u003e⁎\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003eNotes: Data are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD), n (%), or median (P\u003csub\u003e25\u003c/sub\u003e,P\u003csub\u003e75\u003c/sub\u003e). CSI, Cerebral State Index (CSI); LA group, the group underwent adjustment of anesthesia to maintain a CSI value between 50\u0026ndash;59; DA group, the group underwent adjustment of anesthesia to maintain a CSI value between 40\u0026ndash;49; POD, Postoperative delirium; QoR-15, the 15-item quality of recovery scale; VAS, Visual Analogue Scale. ⁎ VAS score on Day 1 and Day 2, Number of POD and the number of presses on the pain pump were significantly higher in DA group compared to LA group; QoR-15 score in DA group was significantly lower than LA group.\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003eThe QoR-15 score was significantly higher in the light anesthesia group compared to the deep anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Although the light anesthesia group had a shorter hospital stay than the deep anesthesia group, this difference was not statistically significant (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). From the first to the third day after surgery, VAS scores and the number of presses on the pain pump were significantly lower in the light anesthesia group compared to the deep anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Additionally, there were no significant differences in the incidence of nausea and vomiting between the two groups (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this randomized controlled trial of elderly patients at pre-frail stage, the overall postoperative delirium incidence was 25.5%. Incidence were 32.9% in the deep anesthesia group and 18.3% in the light anesthesia group. The delirium incidence was significantly reduced in the light anesthesia group compared to the deep anesthesia group, with a reduction of approximately 14%.\u003c/p\u003e \u003cp\u003eA study involving 150 non-cardiac surgeries reported postoperative delirium incidence of 39.3%, 29.8%, and 12.7% for frail, pre-frail, and non-frail patients, respectively [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The delirium incidence in pre-frail patients from that study is similar to the overall postoperative delirium incidence of 25.5% for pre-frail patients in this study. A prospective controlled study using bispectral index monitoring during colon cancer surgery in elderly patients found a delirium incidence of 17.5% in the BIS group [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. This incidence is lower than the overall postoperative delirium incidence in this study, which may be attributed to the focus on pre-frail elderly patients.\u003c/p\u003e \u003cp\u003eFrailty is a prevalent syndrome in the elderly, characterized by heightened vulnerability to both external and internal stressors, which increases the risk of adverse clinical outcomes across various settings [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Pre-frailty is a multi-dimensional concept, an early and reversible risk-state before frailty that can lead to negative healthcare outcomes [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Previous studies assessing the impact of anesthetic depth on postoperative delirium in elderly patients have seldom stratified by frailty status [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Additionally, while various preoperative frailty scoring scales are used in studies of postoperative delirium, their application has been inconsistent [\u003cspan additionalcitationids=\"CR29\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. This study employs the mFI-5 scoring scale, a straightforward and precise tool for identifying frail or pre-frail individuals. It offers an objective method for evaluating frailty status and assessing the risk of complications in surgical patients [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], and provides valuable data on the incidence of postoperative delirium in pre-frail elderly patients undergoing abdominal surgery. Inflammatory marker levels in pre-frail patients are higher compared to those in healthy individuals, serum CRP and IL-6 are significantly elevated in pre-frail people [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], which may be the cause of postoperative delirium in pre-frail patients [\u003cspan additionalcitationids=\"CR35\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA study examining the impact of sedation depth on postoperative delirium following hip fracture repair in elderly patients found that the light sedation group had a lower incidence of postoperative delirium compared to the deep sedation group among patients with fewer complications [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. In this study, the light anesthesia group had a lower rate of postoperative delirium compared to the deep anesthesia group, which is consistent with the study's findings mentioned above. Clinically, monitoring anesthetic depth can reduce the use of general anesthetics and mitigate the risk of adverse events [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Using processed EEG monitoring during anesthesia allows the anesthesiologist to reduce the amount of anesthetic administered, leading to a \"lighter\" level of anesthesia, as indicated by continuous processed EEG numbers such as BIS. This interpretation suggests that the anesthetic itself may be harmful to the brain, and thus reducing the dosage may decrease the incidence of postoperative delirium [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. In this study, the doses of sevoflurane and propofol were significantly lower in the light anesthesia group compared to the deep anesthesia group, which may contribute to the reduced incidence of postoperative delirium. However, the hypothesis that the anesthetic dose directly causes acute brain dysfunction and leads to subsequent delirium in older patients has not been confirmed, and Taylor \u003cem\u003eet al\u003c/em\u003e. found that sevoflurane dose was not associated with the severity and incidence of delirium [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. A study has found that patients with electroencephalogram suppression at lower volatile anesthetic concentrations have an increased incidence of postoperative delirium. Such patients appear to exhibit a phenotype of anesthetic sensitivity, which might predispose them to adverse cognitive outcomes [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Therefore, the depth of anesthesia may simply be a marker for patient\u0026rsquo;s baseline brain vulnerability to the effects of anesthetics. The differentiation between direct effects of anesthetic effects on the brain versus patients\u0026rsquo; baseline vulnerability is critical to understanding the relationship between delirium and the role of the use of processed electroencephalogram-guided anesthesia [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCurrently, there was no definitive conclusion regarding the impact of propofol compared to sevoflurane on the incidence of postoperative delirium [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. This trial used two anesthetic maintenance protocols, but there was no statistical difference in the proportions of these protocols between the two groups. Moreover, the use of two different anesthetic maintenance protocols better reflects the diversity of anesthetic practices in real clinical settings, providing a postoperative delirium incidence rate that more accurately aligns with clinical reality.\u003c/p\u003e \u003cp\u003eIn this study, the MAP in the DA group was lower than in the LA group from T6 to T10, with statistical significance was found at T6, T7, and T9. A retrospective multicenter cohort study found that in patients undergoing noncardiac surgery, a MAP\u0026thinsp;\u0026lt;\u0026thinsp;55 mmHg was associated with a duration-dependent increase in odds of postoperative delirium [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Another study reported that intraoperative hypotension (MAP\u0026thinsp;\u0026le;\u0026thinsp;65 mmHg) for \u0026ge;\u0026thinsp;5 mins was associated with an increased incidence of POD after thoracic and orthopedic surgery in elderly [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. In this trial, only a few time points showed differences in blood pressure between two groups, all of which were within the normal range and had a short duration. Moreover, a recent study found that intraoperative hypotension is not associated with postoperative delirium in elderly patients having elective noncardiac surgery [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Based on the existing studies, we believe that the hypotension in this study did not have a direct impact on the outcomes.\u003c/p\u003e \u003cp\u003eNumerous instruments are employed to monitor anesthetic depth, with bispectral index (BIS) being the most prevalent [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. An ideal anesthetic depth monitoring device should exhibit characteristics such as accuracy, specificity, sensitivity, stability, and robust resistance to interference. The CSI method for monitoring anesthetic depth operates by measuring EEG activity 2000 times per second. Sub-parameters of the EEG signals are processed by a computer-adaptive neuro-fuzzy inference system, which computes the CSI and displays it as a value between 0 and 100. Higher values indicate greater consciousness, while lower values suggest increased cortical suppression. The absolute values and consistency of the CSI are comparable to those of the BIS. Additionally, the CSI demonstrates greater sensitivity and is less prone to electrical interference [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. CSI and BIS show similar variations across different sedation levels; however, CSI is superior in predicting the clinical outcomes of LVC (loss of verbal contact) and LOR (loss of responsiveness) [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Compared to BIS, CSI also offers a precise measurement of anesthetic depth [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. This study utilizes CSI for monitoring anesthetic depth. Besides reflecting the depth index, the device also provides information on the burst suppression ratio, signal quality, and electromyographic activity. This enhances signal accuracy, enables timely detection and correction of transmission faults, and indirectly indicates excessive anesthesia and neuromuscular blockade, thus offering improved insight into intraoperative anesthetic management.\u003c/p\u003e \u003cp\u003eThe mechanism of delirium involves inflammatory responses [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e], with surgical stress exacerbating inflammation [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. Adequate intraoperative analgesia is crucial for reducing surgical stress. Since this study did not monitor pain-related indices, within the set anesthetic depth range, with vital sign fluctuations not exceeding 20%, researchers adjusted the amount of analgesic medication based on changes in patient vital signs. In this study, the light anesthesia group received significantly more remifentanil than the deep anesthesia group, which may have reduced the risk of inadequate intraoperative analgesia. Conversely, the deep anesthesia group exhibited less blood pressure variability, potentially masking signs of insufficient analgesia and leading to increased production of inflammatory mediators during surgery. This may also explain why the postoperative pain scores and the number of presses on the pain pump were higher in the deep anesthesia group compared to the light anesthesia group, with postoperative pain contributing to a higher incidence of delirium.\u003c/p\u003e \u003cp\u003eAlthough the study observed variations in hospital stay durations between the two groups, these differences were not statistically significant. The group receiving light anesthesia demonstrated better postoperative recovery quality compared to the deep anesthesia group, yet this difference was not clinically meaningful. This discrepancy may be attributed to factors such as the recovery of gastrointestinal function influencing the overall quality of postoperative recovery.\u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eLimitations and strengths\u003c/h2\u003e \u003cp\u003eFirst, this study did not collect perioperative inflammatory markers due to considerations regarding patient costs, it was not possible to further explore the impact of changes in inflammatory factors on the incidence of postoperative delirium in patients at the pre-frailty stage. Second, due to the differences in patients' education levels, this study set the inclusion criterion as MMSE score of 15 or higher. This may lead to a higher incidence of postoperative delirium. However, there was no statistically significant difference in MMSE scores between the two groups, so the inclusion criterion did not affect the result that light anesthesia may reduce the incidence of postoperative delirium in patients at the pre-frailty stage.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis randomized controlled trial employed two anesthesia protocols that closer to clinical practice. Moreover, it used a highly reliable frailty scale to screen pre-frail elderly patients and CSI that demonstrates greater sensitivity and is less prone to electrical interference than BIS. This study provided clinical data on the incidence of postoperative delirium following abdominal surgery in elderly patients at pre-frail stage and offered insights into strategies for reducing postoperative delirium incidence in this group. In conclusion, the elderly pre-frail patients under light anesthesia (with high CSI score) may have lower incidence of postoperative delirium and better outcome.\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: 288px;\"\u003e\n \u003cp\u003eCSI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003ecerebral state index\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eBIS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003ebispectral index\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003emFI-5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003ea 5-Item Modified Frailty Index scale\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eLA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003elight anesthesia\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eDA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003edeep anesthesia\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eVAS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003evisual analog scale\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eQoR-15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003ethe 15-item quality of recovery scale\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eBMI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\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: 288px;\"\u003e\n \u003cp\u003eMMSE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eMini-Mental State Examination\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eASA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eAmerican Society of Anesthesiology classification\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eCOPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eChronic obstructive pulmonary disease\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eTIVA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003etotal intravenous anesthesia\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eMAP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eMean arterial pressure\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003eHR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\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: 288px;\"\u003e\n \u003cp\u003ePOD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 288px;\"\u003e\n \u003cp\u003ePostoperative delirium\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\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthical approval (No. 2024ER194-1) was granted by the Medical Ethics Committee of Affiliated Hospital of North Sichuan Medical College in April 2024. All patients provided written informed consent prior to enrollment, and all procedures were conducted in accordance with the Helsinki Declaration.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent for information collection for research was obtained from all participants and the hospital review board provided us with consent for publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to conceptualization and methodology. The first draft of the manuscript was written by RMC. Formal analysis was performed by HQM and SYJ. Data curation and investigation were performed by PFH. Project administration and supervision was performed by WXL. All authors commented on previous versions of the manuscript. The review and editing was performed by JYL. All authors read and approved the final manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to express our sincere gratitude to the gastrointestinal surgeons and nurses who provided strong support for this study, to the patients who contributed to this trial, and to the colleagues who assisted with this research.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLiang CK, Chu CL, Chou MY, Lin YT, Lu T, Hsu CJ, Chen LK: \u003cstrong\u003eInterrelationship of postoperative delirium and cognitive impairment and their impact on the functional status in older patients undergoing orthopaedic surgery: a prospective cohort study\u003c/strong\u003e. \u003cem\u003ePLoS One \u003c/em\u003e2014, \u003cstrong\u003e9\u003c/strong\u003e(11):e110339.\u003c/li\u003e\n\u003cli\u003eRudolph JL, Marcantonio ER: \u003cstrong\u003eReview articles: postoperative delirium: acute change with long-term implications\u003c/strong\u003e. \u003cem\u003eAnesthesia and Analgesia \u003c/em\u003e2011, \u003cstrong\u003e112\u003c/strong\u003e(5):1202-1211.\u003c/li\u003e\n\u003cli\u003eVasilevskis EE, Han JH, Hughes CG, Ely EW: \u003cstrong\u003eEpidemiology and risk factors for delirium across hospital settings\u003c/strong\u003e. \u003cem\u003eBest Pract Res Clin Anaesthesiol \u003c/em\u003e2012, \u003cstrong\u003e26\u003c/strong\u003e(3):277-287.\u003c/li\u003e\n\u003cli\u003eBramley P, McArthur K, Blayney A, McCullagh I: \u003cstrong\u003eRisk factors for postoperative delirium: An umbrella review of systematic reviews\u003c/strong\u003e. \u003cem\u003eInt J Surg \u003c/em\u003e2021, \u003cstrong\u003e93\u003c/strong\u003e:106063.\u003c/li\u003e\n\u003cli\u003eChong E, Ho E, Baldevarona-Llego J, Chan M, Wu L, Tay L: \u003cstrong\u003eFrailty and Risk of Adverse Outcomes in Hospitalized Older Adults: A Comparison of Different Frailty Measures\u003c/strong\u003e. \u003cem\u003eJ Am Med Dir Assoc \u003c/em\u003e2017, \u003cstrong\u003e18\u003c/strong\u003e(7).\u003c/li\u003e\n\u003cli\u003eChen C-L, Chen C-M, Wang C-Y, Ko P-W, Chen C-H, Hsieh C-P, Chiu H-C: \u003cstrong\u003eFrailty is Associated with an Increased Risk of Major Adverse Outcomes in Elderly Patients Following Surgical Treatment of Hip Fracture\u003c/strong\u003e. \u003cem\u003eScientific Reports \u003c/em\u003e2019, \u003cstrong\u003e9\u003c/strong\u003e(1):19135.\u003c/li\u003e\n\u003cli\u003eSousa-Santos AR, Afonso C, Moreira P, Padr\u0026atilde;o P, Santos A, Borges N, Amaral TF: \u003cstrong\u003eWeakness: The most frequent criterion among pre-frail and frail older Portuguese\u003c/strong\u003e. \u003cem\u003eArch Gerontol Geriatr \u003c/em\u003e2018, \u003cstrong\u003e74\u003c/strong\u003e:162-168.\u003c/li\u003e\n\u003cli\u003eSacha J, Sacha M, Soboń J, Borysiuk Z, Feusette P: \u003cstrong\u003eIs It Time to Begin a Public Campaign Concerning Frailty and Pre-frailty? 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\u003cem\u003eAnesthesiology \u003c/em\u003e2024, \u003cstrong\u003e141\u003c/strong\u003e(4):707-718.\u003c/li\u003e\n\u003cli\u003eZhong T, Guo QL, Pang YD, Peng LF, Li CL: \u003cstrong\u003eComparative evaluation of the cerebral state index and the bispectral index during target-controlled infusion of propofol\u003c/strong\u003e. \u003cem\u003eBr J Anaesth \u003c/em\u003e2005, \u003cstrong\u003e95\u003c/strong\u003e(6):798-802.\u003c/li\u003e\n\u003cli\u003eBrattinga B, Plas M, Spikman JM, Rutgers A, de Haan JJ, Absalom AR, van der Wal-Huisman H, de Bock GH, van Leeuwen BL: \u003cstrong\u003eThe association between the inflammatory response following surgery and post-operative delirium in older oncological patients: a prospective cohort study\u003c/strong\u003e. \u003cem\u003eAge Ageing \u003c/em\u003e2022, \u003cstrong\u003e51\u003c/strong\u003e(2).\u003c/li\u003e\n\u003cli\u003eAlam A, Hana Z, Jin Z, Suen KC, Ma D: \u003cstrong\u003eSurgery, neuroinflammation and cognitive impairment\u003c/strong\u003e. \u003cem\u003eEBioMedicine \u003c/em\u003e2018, \u003cstrong\u003e37\u003c/strong\u003e:547-556.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"perioperative-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"peri","sideBox":"Learn more about [Perioperative Medicine](http://perioperativemedicinejournal.biomedcentral.com)","snPcode":"13741","submissionUrl":"https://submission.nature.com/new-submission/13741/3","title":"Perioperative Medicine","twitterHandle":"@EMSurgeryBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"anesthesia, electroencephalography, postoperative delirium, elderly, Pre-frailty","lastPublishedDoi":"10.21203/rs.3.rs-5950908/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5950908/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e \u003cp\u003eMonitoring anesthetic depth may reduce the incidence of postoperative delirium in patients undergoing general anesthesia. This study investigated the impact of varying readings of Cerebral State Index (CSI) on postoperative delirium in elderly pre-frail patients undergoing abdominal surgery.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA total of 150 elderly pre-frail patients aged over 65 years scheduled for selective abdominal surgery under general anesthesia were enrolled. Pre-frailty was defined as a 5-Item Modified Frailty Index (mFI-5) score of 1\u0026ndash;2. Patients in the light anesthesia (LA) group were maintained a CSI value between 50\u0026ndash;59, while patients in the deep anesthesia (DA) group were maintained a CSI value between 40\u0026ndash;49. The incidence of delirium within three days postoperatively, as well as visual analog scale (VAS) scores, postoperative nausea, vomiting, and the 15-item quality of recovery (QoR-15) scale scores on the first postoperative day were recorded and compared.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe incidence of postoperative delirium was approximately 14% lower in the light anesthesia group compared to the deep anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The QoR-15 scale scores on the first postoperative day were significantly higher in the light anesthesia group than in the deep anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In contrast, the VAS scores over the three days following surgery were significantly higher in the deep anesthesia group than in the light anesthesia group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThe elderly pre-frail patients under light anesthesia (with high CSI score) may have lower incidence of postoperative delirium and better outcome.\u003c/p\u003e\u003ch2\u003eTrial registration:\u003c/h2\u003e \u003cp\u003eChiCTR2400083016, Date of registration: 15/04/2025.\u003c/p\u003e","manuscriptTitle":"Influence of different anesthetic depth on postoperative delirium in elderly pre-frail patients undergoing abdominal surgery","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-11 09:55:46","doi":"10.21203/rs.3.rs-5950908/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-04-28T17:14:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-19T13:33:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-17T07:43:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"310866045028199244483916153212603367491","date":"2025-04-11T09:10:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"59137858695596149096708492905023677331","date":"2025-04-07T18:07:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"134568110998254927254337985571687777271","date":"2025-04-05T05:46:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"112966657581793693183512088297717369804","date":"2025-03-16T15:59:31+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-16T00:26:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"208629034687494188139223088369596272321","date":"2025-03-15T04:19:59+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-14T15:42:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-02-10T11:54:59+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-02-06T09:51:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Perioperative Medicine","date":"2025-02-03T11:59:30+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"perioperative-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"peri","sideBox":"Learn more about [Perioperative Medicine](http://perioperativemedicinejournal.biomedcentral.com)","snPcode":"13741","submissionUrl":"https://submission.nature.com/new-submission/13741/3","title":"Perioperative Medicine","twitterHandle":"@EMSurgeryBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"124a01c9-d3ca-4e6a-9463-db1d98eaff7b","owner":[],"postedDate":"February 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-08-04T16:47:18+00:00","versionOfRecord":{"articleIdentity":"rs-5950908","link":"https://doi.org/10.1186/s13741-025-00561-5","journal":{"identity":"perioperative-medicine","isVorOnly":false,"title":"Perioperative Medicine"},"publishedOn":"2025-07-28 16:38:19","publishedOnDateReadable":"July 28th, 2025"},"versionCreatedAt":"2025-02-11 09:55:46","video":"","vorDoi":"10.1186/s13741-025-00561-5","vorDoiUrl":"https://doi.org/10.1186/s13741-025-00561-5","workflowStages":[]},"version":"v1","identity":"rs-5950908","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5950908","identity":"rs-5950908","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}