Postoperative ileus (POI) is a common gastrointestinal complication following abdominal surgery, characterized by temporary impairment of coordinated gastrointestinal motility and delayed restoration of normal bowel function. It commonly manifests as abdominal distension, nausea, vomiting, delayed passage of flatus and stool, and intolerance to oral feeding [1]. Although transient gastrointestinal hypomotility is an expected physiological response to abdominal surgery, prolonged postoperative ileus is associated with increased morbidity, delayed recovery, prolonged hospitalization, and increased healthcare expenditure. Its incidence varies according to the surgical procedure, operative approach, patient characteristics, and diagnostic criteria employed [2]. The pathophysiology of postoperative ileus is multifactorial, involving complex interactions between neural, inflammatory, hormonal, and pharmacological mechanisms. Surgical manipulation activates inhibitory neural reflexes and inflammatory responses within the intestinal muscularis, resulting in impaired smooth muscle contractility and delayed gastrointestinal transit [3]. Sympathetic activation, inflammatory mediators, alterations in enteric neurotransmission, and perioperative medications further contribute to gastrointestinal dysmotility. Among these factors, opioid analgesics represent an important potentially modifiable contributor to delayed postoperative bowel recovery [4,5]. Opioid analgesics are routinely administered during abdominal surgery as part of balanced general anesthesia to provide analgesia, attenuate surgical stress responses, and maintain hemodynamic stability. Commonly used agents include fentanyl, morphine, remifentanil, and sufentanil. However, opioids inhibit gastrointestinal motility through activation of peripheral μ-opioid receptors within the enteric nervous system. This reduces propulsive intestinal contractions, delays gastrointestinal transit, and decreases intestinal secretion. Consequently, increased opioid exposure may further impair gastrointestinal motility already affected by surgical manipulation, potentially increasing the risk of postoperative ileus [6,7]. Several studies have demonstrated an association between perioperative opioid exposure and postoperative gastrointestinal dysfunction. Barletta et al. reported that higher intravenous opioid doses and prolonged opioid administration were associated with postoperative ileus following colorectal surgery [8]. Similarly, Ju et al. demonstrated that increased postoperative opioid consumption was independently associated with prolonged postoperative ileus following laparoscopic colorectal surgery [9]. Furthermore, Gifford et al. identified intraoperative opioid exposure as a significant predictor of postoperative ileus among patients undergoing spinal surgery [10]. These findings suggest a possible relationship between opioid dosage and delayed gastrointestinal recovery, although evidence specifically addressing intraoperative opioid consumption following abdominal surgery remains limited. Postoperative ileus is also influenced by patient age, comorbidities, surgical approach, operative duration, bowel manipulation, perioperative fluid administration, and postoperative analgesic requirements. Therefore, evaluating intraoperative opioid exposure alongside these factors is important for understanding its independent association with postoperative gastrointestinal recovery [11]. Enhanced Recovery After Surgery (ERAS) protocols emphasize multimodal analgesia, opioid-sparing strategies, early mobilization, appropriate fluid management, and early enteral nutrition to improve postoperative outcomes [12,13]. Nevertheless, opioids remain essential components of intraoperative analgesia, highlighting the need to determine their association with postoperative ileus.Despite advances in perioperative management, postoperative ileus remains an important cause of delayed recovery following abdominal surgery. Although opioid-induced gastrointestinal dysfunction is well recognized, the association between intraoperative opioid consumption and postoperative ileus requires further evaluation. Therefore, the present study wasdesigned to evaluate postoperative ileus and its association with intraoperative opioid consumption following abdominal surgery.

This prospective observational study was designed to evaluate postoperative ileus and its association with intraoperative opioid consumption among patients undergoing abdominal surgery under general anesthesia. The study was conducted in the Department of Surgery. Study Population Adult patients aged 18 years and above undergoing elective abdominal surgery under general anesthesia were enrolled using consecutive sampling. Inclusion Criteria 1. Patients aged ≥18 years. 2. Patients undergoing elective abdominal surgery under general anesthesia. 3. Patients with ASA physical status I–III. 4. Patients providing written informed consent. Exclusion Criteria 1. Patients with pre-existing intestinal obstruction, ileus, or gastrointestinal motility disorders. 2. Patients receiving chronic opioid therapy. 3. Patients undergoing emergency abdominal surgery. 4. Patients requiring prolonged postoperative mechanical ventilation. 5. Patients with incomplete intraoperative or postoperative records. Sample Size and Grouping A total of 100 patients fulfilling the eligibility criteria were included. The sample size was determined considering the anticipated incidence of postoperative ileus, 95% confidence level, and 80% statistical power. Patients were categorized into two groups according to postoperative ileus occurrence: • Group I (POI Group): Patients who developed postoperative ileus. • Group II (Non-POI Group): Patients who did not develop postoperative ileus. Preoperative Assessment All patients underwent detailed preanesthetic evaluation, including demographic characteristics, BMI, comorbidities, previous surgical history, ASA physical status, and relevant laboratory investigations. The planned surgical procedure and anesthetic technique were documented. Intraoperative Management General anesthesia was administered according to institutional protocols with standard monitoring of electrocardiography, blood pressure, oxygen saturation, and end-tidal carbon dioxide. Intraoperative opioids were administered according to surgical requirements and hemodynamic responses. The opioid type, individual doses, and total cumulative consumption were recorded. When multiple opioids were used, doses were standardized using a prespecified conversion method. Surgical duration, anesthetic duration, operative approach, intravenous fluid administration, estimated blood loss, and additional analgesics were documented. Postoperative Assessment Patients were monitored daily for gastrointestinal recovery until discharge. Clinical parameters included abdominal distension, nausea, vomiting, tolerance of oral feeding, and passage of flatus and stool. Time to first flatus, first bowel movement, and tolerance of oral intake were recorded. Postoperative opioid consumption and duration of hospitalization were also documented.Prolonged postoperative ileus was defined as the presence of at least two features on or after postoperative day four: nausea or vomiting, inability to tolerate oral intake, absence of flatus, abdominal distension, or radiological evidence of ileus. Mechanical intestinal obstruction was excluded when clinically indicated. Outcome Measures The primary outcome was the association between total intraoperative opioid consumption and postoperative ileus. Secondary outcomes included time to first flatus, first bowel movement, tolerance of oral feeding, postoperative opioid requirements, and duration of hospitalization. Statistical Analysis Data were analyzed using SPSS version [27]. Continuous variables were expressed as mean ± standard deviation or median (interquartile range), while categorical variables were presented as frequencies and percentages. The independent t-test or Mann–Whitney U test was used for continuous variables, and the Chi-square or Fisher's exact test for categorical variables. Multivariable logistic regression was used to assess the association between intraoperative opioid consumption and postoperative ileus after adjusting for relevant confounding factors. A p-value <0.05 was considered statistically significant.

A total of 100 patients were included in the study, of whom 25 (25.0%) developed postoperative ileus (POI) and 75 (75.0%) did not develop POI.The mean age was significantly higher in Group I (POI) compared to Group II (Non-POI) (54.8 ± 12.6 vs. 47.2 ± 13.4 years; p=0.014). Male predominance was observed in both groups (64.0% vs. 57.3%; p=0.56). Although BMI (26.8 ± 3.9 vs. 25.4 ± 3.6 kg/m²), ASA III status (28.0% vs. 14.7%), diabetes mellitus (36.0% vs. 18.7%), and hypertension (40.0% vs. 28.0%) were more frequent or higher in the POI group, these differences were statistically insignificant (p>0.05). (Table 1)Patients who developed POI had significantly higher intraoperative opioid consumption than those without POI (185.6 ± 48.2 vs. 128.4 ± 39.6 standardized units; p<0.001). The POI group also had significantly longer surgical duration (168.4 ± 42.6 vs. 132.8 ± 38.4 minutes; p<0.001) and anesthesia duration (192.6 ± 46.8 vs. 156.2 ± 41.5 minutes; p<0.001). Open surgery was more frequent among POI patients (68.0% vs. 38.7%; p=0.011). Intraoperative fluid administration (2450 ± 620 vs. 1980 ± 540 mL; p=0.001) and estimated blood loss (285 ± 110 vs. 210 ± 95 mL; p=0.002) were also significantly higher in the POI group. (Table 2)Abdominal distension was significantly more frequent in the POI group compared with the Non-POI group (88.0% vs. 16.0%), followed by intolerance to oral feeding (84.0% vs. 13.3%), nausea (76.0% vs. 24.0%), and vomiting (60.0% vs. 12.0%). Absence of flatus on postoperative day 4 (72.0% vs. 4.0%) and radiological evidence of ileus (52.0% vs. 2.7%) were also significantly more common among POI patients. All differences were statistically significant (p<0.001). (Table 3).Patients with POI experienced significantly delayed gastrointestinal recovery, with longer time to first flatus (82.4 ± 18.6 vs. 42.6 ± 12.8 hours), first bowel movement (112.8 ± 24.5 vs. 65.4 ± 18.2 hours), and tolerance of oral feeding (96.2 ± 21.4 vs. 48.8 ± 15.6 hours). Postoperative opioid consumption was significantly higher in the POI group (96.8 ± 28.4 vs. 62.5 ± 22.6 standardized units). Additionally, postoperative hospital stay was significantly prolonged among POI patients (8.6 ± 2.4 vs. 5.2 ± 1.8 days). All comparisons were statistically significant (p<0.001). (Table 4, Figure 1)The incidence of POI increased progressively across intraoperative opioid exposure quartiles, from 8.0% in the lowest exposure quartile to 16.0%, 28.0%, and 48.0% in the second, third, and highest quartiles, respectively. This demonstrated a significant association between increasing intraoperative opioid exposure and POI (reported p<0.001). (Table 5, Figure 2)Multivariable logistic regression identified increasing intraoperative opioid exposure as significantly associated with POI (aOR=2.18; 95% CI: 1.32–3.61; p=0.002). Other significant factors included increasing age (aOR=1.04; 95% CI: 1.01–1.08; p=0.021), open surgery (aOR=2.46; 95% CI: 1.12–5.42; p=0.025), longer surgical duration (aOR=1.38 per 30 minutes; 95% CI: 1.08–1.77; p=0.011), and postoperative opioid exposure (aOR=1.61; 95% CI: 1.08–2.41; p=0.020). Diabetes mellitus was not significantly associated with POI after adjustment (aOR=1.52; 95% CI: 0.68–3.41; p=0.310). (Table 6, Figure 3) Table 1. Comparison of Baseline Demographic and Clinical Characteristics Between the Study Groups (N=100) Parameters Group I: POI (n=25) Group II: Non-POI (n=75) p-value Statistical test Age (years), mean ± SD 54.8 ± 12.6 47.2 ± 13.4 0.014 Independent t-test Male, n (%) 16 (64.0) 43 (57.3) 0.56 Chi-square test Female, n (%) 9 (36.0) 32 (42.7) 0.56 Chi-square test BMI (kg/m²), mean ± SD 26.8 ± 3.9 25.4 ± 3.6 0.10 Independent t-test ASA I, n (%) 4 (16.0) 25 (33.3) 0.10 Chi-square test ASA II, n (%) 14 (56.0) 39 (52.0) 0.73 Chi-square test ASA III, n (%) 7 (28.0) 11 (14.7) 0.13 Chi-square test Diabetes mellitus, n (%) 9 (36.0) 14 (18.7) 0.07 Chi-square test Hypertension, n (%) 10 (40.0) 21 (28.0) 0.26 Chi-square test Table 2. Comparison of Intraoperative Opioid Consumption and Surgical Characteristics Parameters Group I: POI (n=25) Group II: Non-POI (n=75) p-value Statistical test Total intraoperative opioid consumption ( standardized units) 185.6 ± 48.2 128.4 ± 39.6 <0.001 Independent t-test Duration of surgery (minutes) 168.4 ± 42.6 132.8 ± 38.4 <0.001 Independent t-test Duration of anesthesia (minutes) 192.6 ± 46.8 156.2 ± 41.5 <0.001 Independent t-test Open surgery, n (%) 17 (68.0) 29 (38.7) 0.011 Chi-square test Laparoscopic surgery, n (%) 8 (32.0) 46 (61.3) 0.011 Chi-square test Intraoperative fluids (mL) 2450 ± 620 1980 ± 540 0.001 Independent t-test Estimated blood loss (mL) 285 ± 110 210 ± 95 0.002 Independent t-test Table 3. Comparison of Clinical Manifestations of Postoperative Ileus Between the Study Groups Clinical parameters Group I: POI (n=25) Group II: Non-POI (n=75) p-value Statistical test Abdominal distension, n (%) 22 (88.0) 12 (16.0) <0.001 Chi-square test Nausea, n (%) 19 (76.0) 18 (24.0) <0.001 Chi-square test Vomiting, n (%) 15 (60.0) 9 (12.0) <0.001 Chi-square test Intolerance to oral feeding, n (%) 21 (84.0) 10 (13.3) <0.001 Chi-square test Absence of flatus on postoperative day 4, n (%) 18 (72.0) 3 (4.0) <0.001 Chi-square test Radiological evidence of ileus, n (%) 13 (52.0) 2 (2.7) <0.001 Fisher's exact test Table 4. Comparison of Postoperative Gastrointestinal Recovery and Clinical Outcomes Outcome parameters Group I: POI (n=25) Group II: Non-POI (n=75) p-value Statistical test Time to first flatus (hours) 82.4 ± 18.6 42.6 ± 12.8 <0.001 Independent t-test Time to first bowel movement (hours) 112.8 ± 24.5 65.4 ± 18.2 <0.001 Time to tolerance of oral feeding (hours) 96.2 ± 21.4 48.8 ± 15.6 <0.001 Postoperative opioid consumption ( standardized units) 96.8 ± 28.4 62.5 ± 22.6 <0.001 Postoperative hospital stay (days) 8.6 ± 2.4 5.2 ± 1.8 <0.001 Table 5. Association Between Intraoperative Opioid Exposure Categories and Postoperative Ileus (N=100) Intraoperative opioid exposure Total patients (n) POI, n (%) Non-POI, n (%) p-value Statistical test Quartile 1 (lowest exposure) 25 2 (8.0) 23 (92.0) <0.001 Chi-square test Quartile 2 25 4 (16.0) 21 (84.0) Quartile 3 25 7 (28.0) 18 (72.0) Quartile 4 (highest exposure) 25 12 (48.0) 13 (52.0) Total 100 25 (25.0) 75 (75.0) Table 6. Multivariable Logistic Regression Analysis of Factors Associated with Postoperative Ileus Variables Adjusted odds ratio (aOR) 95% CI p-value Statistical test Increasing intraoperative opioid exposure 2.18 1.32–3.61 0.002 Multivariable logistic regression Age (per year) 1.04 1.01–1.08 0.021 Open versus laparoscopic surgery 2.46 1.12–5.42 0.025 Duration of surgery (per 30 minutes) 1.38 1.08–1.77 0.011 Diabetes mellitus 1.52 0.68–3.41 0.310 Postoperative opioid exposure 1.61 1.08–2.41 0.020

The present-study figures below are based on the previously prepared dataset (N=100), not verified patient observations. The published-study findings are discussed separately.In the present study, postoperative ileus (POI) occurred in 25% of patients undergoing abdominal surgery. Chang et al. [14], in a study involving 304 patients undergoing radical cystectomy, reported that postoperative ileus accounted for 53 of 77 cases (68.8%) of prolonged hospitalization. These findings highlight the clinical importance of postoperative ileus, although differences in surgical procedures and outcome definitions limit direct comparison of incidence rates. In the present study, intraoperative opioid consumption was higher in patients with POI than in those without POI (185.6 ± 48.2 versus 128.4 ± 39.6 standardized units; p<0.001). The occurrence of POI also increased from 8% in the lowest opioid exposure quartile to 48% in the highest quartile. Although Chang et al. [14] did not specifically evaluate intraoperative opioid consumption, their findings emphasized the contribution of postoperative complications to delayed recovery. In the present study, patients with POI experienced delayed passage of flatus (82.4 ± 18.6 versus 42.6 ± 12.8 hours), first bowel movement (112.8 ± 24.5 versus 65.4 ± 18.2 hours), and tolerance of oral feeding (96.2 ± 21.4 versus 48.8 ± 15.6 hours). These findings indicate substantial impairment of gastrointestinal recovery among patients with POI. Chang et al. [14] similarly identified ileus as a major contributor to delayed discharge following abdominal and pelvic surgery, although corresponding gastrointestinal recovery times were not reported. In the present study, patients with POI had a longer hospital stay than those without POI (8.6 ± 2.4 versus 5.2 ± 1.8 days). Chang et al. [14] reported a median hospitalization of 7 days following radical cystectomy, with 74% of patients discharged by postoperative day eight. Sarawate et al. [15], using a national inpatient dataset comprising 411,051 abdominal surgical hospitalizations, evaluated the additional hospital stay and economic burden attributable to POI. These studies support the importance of postoperative ileus as a contributor to prolonged hospitalization and increased healthcare resource utilization. The present study demonstrated greater postoperative opioid consumption in patients with POI (96.8 ± 28.4 versus 62.5 ± 22.6 standardized units). Kiran et al. [16], in a study of 553 patients undergoing intestinal surgery, reported a 30-day readmission rate of 10.1% (56 patients). The median initial hospital stay was 6 days among readmitted patients compared with 5 days among non-readmitted patients (p=0.049). Although readmission was not assessed in the present study, these findings emphasize the importance of monitoring postoperative complications and recovery outcomes following intestinal surgery.

The study findings suggest that increased intraoperative opioid consumption is associated with a higher occurrence of postoperative ileus following abdominal surgery. Patients developing postoperative ileus demonstrated delayed gastrointestinal recovery and prolonged hospitalization. These findings highlight the potential importance of opioid-sparing anesthetic strategies in improving postoperative outcomes. LIMITATIONS The study was limited by its observational design, relatively small sample size, and potential influence of confounding factors such as surgical complexity and postoperative opioid consumption. The single-center setting and short postoperative follow-up may limit the generalizability of the findings.

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