Despite the effectiveness of bariatric surgery for severe obesity, reoperation and acute kidney injury (AKI) remain significant complications. The impact of volatile anaesthetics on postoperative outcomes is unclear, and current guidelines lack evidence-based recommendations for anaesthetic selection. We investigated the association between cumulative volatile anaesthetic exposure and postoperative complications following bariatric surgery.

This multicentre retrospective study included patients undergoing laparoscopic bariatric procedures at four Israeli centres (January 2017–May 2025). Volatile anaesthetic exposure was quantified as age-adjusted minimum alveolar concentration-hours (MAC _hr ). We examined associations with reoperation (within 30 days) and AKI (within 7 days) and compared agent-specific effects using mixed-effects logistic regression.

A total of 16,685 patients were included in the final analysis. Reoperation occurred in 122 patients (0.7 %) and AKI in 96 patients (0.6 %). Higher total MAC _hr exposure was independently associated with increased reoperation (OR 1.75, 95 % CI 1.35, 2.26; P   <  0.001), and AKI (OR 1.35, 95 % CI 1.05, 1.70; P  = 0.015). While isoflurane and sevoflurane showed comparable associations with reoperation risk, only sevoflurane increased AKI risk (OR 1.53, 95 % CI 1.20, 1.90; P   <  0.001) versus no association with isoflurane (OR 0.89, 95 % CI 0.55, 1.38; P  = 0.630), with a significant difference between these agents ( P  = 0.012).

Cumulative volatile anaesthetic exposure was independently associated with increased postoperative complications following bariatric surgery. The association with reoperation rate appears to be a class effect, while sevoflurane, but not isoflurane, is associated with an increased risk of AKI. However, these observational associations may be influenced by residual confounding. These hypothesis-generating findings require prospective validation before clinical recommendations can be made.