Differences in inflammatory responses between men and women may contribute to sex disparities in cardiac surgery outcomes. We investigated how sex differences influence systemic inflammatory response syndrome (SIRS) and adverse outcomes after cardiac surgery.

A single-centre retrospective cohort study of patients undergoing cardiac surgery from 2018 to 2020 was performed. SIRS was defined as per the American College of Chest Physicians/Society of Critical Care Medicine. Predictors of SIRS and composite adverse outcomes (death, transient ischaemic attack/stroke, renal therapy, bleeding, postcardiotomy mechanical circulatory support, prolonged Intensive Care Unit stay) were evaluated using multivariable logistic regression. Mediation effects of SIRS were assessed using structural equation modelling.

The cohort included 1005 patients, of whom 299 (29.8%) were women. SIRS occurred in 28.1% of patients, and 12.7% experienced the composite end point. Female sex was significantly associated with SIRS (odds ratio 1.56; 95% confidence interval 1.12–2.18, P = 0.009) and the composite outcome (odds ratio 1.72; 95% confidence interval 1.10–2.69, P = 0.017). Baseline left ventricular dysfunction and intraoperative hyperlactatemia were additional common predictors. SIRS mediated 50.8% of the effect of female sex, 17.0% of left ventricular dysfunction and 30.9% of intraoperative hyperlactatemia on the composite outcome.

Female sex is independently associated with postoperative SIRS and poorer outcomes. Systemic inflammation, preoperative anaemia and procedural hyperlactatemia are potentially modifiable factors in the mechanisms through which female sex appears to worsen outcome after cardiac surgery.