The Association Between Body Mass Index and Acute Postoperative Pain in Bariatric Surgery Patients: A Prospective Cohort Study

The rising global prevalence of obesity has established bariatric surgery as a key therapeutic option; however, postoperative pain management remains a challenge. This study investigated the influence of body mass index (BMI) stratification on acute postoperative pain in patients undergoing bariatric surgery. Fifty-five patients aged 18–65 years with BMI ≥ 30 kg/m2 scheduled for laparoscopic sleeve gastrectomy were categorized into the obesity group (O group; 30 kg/m2 ≤ BMI < 40 kg/m2) and the severe obesity group (SO group; BMI ≥ 40 kg/m2). Preoperative pain threshold and pain tolerance threshold, perioperative inflammatory cytokines, Brief Pain Inventory (BPI) scores, Quality of Recovery-15 (QoR-15) scores, postoperative resting and movement numeric rating scale (NRS) scores, patient-controlled analgesia (PCA) pump usage, cumulative analgesic consumption, and analgesic satisfaction were assessed. Compared with the O group, the SO group demonstrated a significantly higher pain tolerance threshold (4.1 ± 0.8 vs. 3.5 ± 1.0, P < 0.01), along with lower demand for PCA and reduced consumption of cumulative morphine milligram equivalents and flurbiprofen (P < 0.05). Notably, the primary outcome, the 24-h BPI score, showed no significant difference between the two groups. On postoperative days 1 and 3, tumor necrosis factor-α (TNF-α) levels were significantly lower in the O group, whereas no significant intergroup differences were observed in other inflammatory cytokines. No significant differences were observed in NRS or QoR-15 scores between the two groups. BMI may be considered as a factor for stratifying postoperative analgesia, favoring multimodal, opioid-sparing strategies in patients with severe obesity who demonstrate higher pain tolerance and lower analgesic requirements. Chinese Clinical Trial Registry, ChiCTR2400095080.