To investigate the effect of the timing of prophylactic ondansetron administration on postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic sleeve gastrectomy (LSG).

This retrospective study reviewed the clinical records of 110 patients who underwent elective LSG at the Bariatric and Metabolic Center of Dalang Hospital, Dongguan, China, between January 2023 and December 2025. Among these patients, 93 eligible cases were included in the final analysis. All procedures were performed by the same surgical and anesthesia team using a standardized three-port, seven-step LSG technique. Patients were divided into two groups according to the timing of prophylactic ondansetron administration: 46 patients received ondansetron at anesthesia induction (group G1), whereas 47 patients received the drug during gastric sleeve formation (group G2). Both groups received identical postoperative antiemetic and analgesic regimens, including the same rescue protocols. Baseline clinical characteristics, the frequency and severity of PONV, rescue antiemetic use, postoperative VAS pain scores, and number of rescue analgesic administrations were compared between the two groups at 0-6 h (T1), 6-12 h (T2), 12-18 h (T3), 18-24 h (T4), and 24-48 h (T5) after surgery.

No significant differences were observed between the two groups with respect to baseline characteristics, including age, sex, body mass index (BMI), and anesthesia duration (all P>0.05). Compared with Group G1, Group G2 had significantly fewer episodes of postoperative nausea and vomiting (PONV) at T1 [1 (1-1) vs 2 (2-3)], T2[2 (1-3) vs 3.5 (3-4)], and T3 [0 (0-1) vs 1 (0-1)] (all P<0.05). Similarly, the median PONV severity scores were significantly lower in Group G2 than in Group G1 at T1 [2 (1-3) vs 3 (3-4)] and T2 [3 (2-4) vs 4 (3-5)] (both P<0.05). In addition, the median postoperative visual analog scale (VAS) pain scores were significantly lower in Group G2 than in Group G1 at T1, T2, and T4 (all P<0.05).

Compared with administration during anesthesia induction, prophylactic administration of ondansetron during gastric sleeve creation more effectively reduces the incidence and severity of early postoperative nausea and vomiting and alleviates postoperative pain in patients with obesity undergoing laparoscopic sleeve gastrectomy.