Association of anaesthesia provider sex with perioperative complications: a two-centre retrospective cohort study

Background: Previous studies suggested that surgeon sex is associated with differential patient outcomes. Whether this also applies to anaesthesia providers is unclear. We hypothesised that female sex of the primary anaesthesia provider is associated with lower risk of perioperative complications. Methods: The first case for all adult patients undergoing anaesthesia care between 2008 and 2022 at two academic healthcare networks in the USA was included in this retrospective cohort study. The primary exposure was the sex of the anaesthesia provider who spent the most time in the operating theatre during the case. The primary outcome was intraoperative complications, defined as hypotension (mean arterial blood pressure <55 mm Hg for ≥5 cumulative minutes) or hypoxaemia (oxygen saturation <90% for >2 consecutive minutes). The co-primary outcome was 30-day adverse postoperative events (including complications, readmission, and mortality). Analyses were adjusted for a priori defined confounders. Results: Among 364,429 included patients, 57,550 (15.8%) experienced intraoperative complications and 55,168 (15.1%) experienced adverse postoperative events. Care by female compared with male anaesthesia providers was associated with lower risk of intraoperative complications (adjusted odds ratio [aOR] 0.95, 95% confidence interval [CI] 0.94–0.97, P<0.001), which was magnified among non-trainees (aOR 0.84, 95% CI 0.82–0.87, P-for-interaction<0.001). Anaesthesia provider sex was not associated with the composite of adverse postoperative events (aOR 1.00, 95% CI 0.98–1.02, P=0.88). Conclusions: Care by a female anaesthesia provider was associated with a lower risk of intraoperative complications, which was magnified among non-trainees. Future studies should investigate underlying mechanisms.