Associations between perioperative risk factors and surgical site infection in colorectal surgery: mediating effects of intra-operative blood loss.

BACKGROUND AND AIMS: Surgical site infection (SSI) is a prevalent and consequential complication following colorectal surgery. While perioperative factors are associated with increased SSI risk, the mechanisms underlying these associations remain unclear. This study investigated whether and to what extent intra-operative blood loss mediates the association between perioperative risk factors and SSI.

METHODS

This prospective study included 5530 patients who underwent colorectal surgery between January 2020 and December 2023. Patients were followed for 30 days postoperatively. Logistic regression analysis was used to identify independent SSI risk factors, and causal mediation analysis quantified the mediating effect of intra-operative blood loss.

RESULTS

The study included 5530 individuals, of whom 131 developed SSI. Operating time (odds ratio [OR]: 1.90, 95% confidence interval [CI]: 1.66-2.18), emergency surgery (OR: 3.31, 95% CI: 1.40-7.08), pre-operative chemotherapy (OR: 1.67, 95% CI: 1.10-2.47), and pre-operative hypoalbuminaemia (OR: 4.05, 95% CI: 1.32-10.09) were independently associated with increased SSI risk. Subgroup analyses revealed no significant effect modification of the identified risk factors for SSI across different subpopulations. Furthermore, intra-operative blood loss mediated the associations of operating time, emergency surgery, pre-operative chemotherapy, and pre-operative hypoalbuminaemia with SSI, with mediation proportions of 7.23% (95% CI: 0.53%-13.90%), 10.01% (95% CI: 3.08%-16.90%), 6.39% (95% CI: 0.55%-12.20%), and 13.01% (95% CI: 0.89%-25.10%), respectively.

CONCLUSIONS

This study revealed significant associations between perioperative risk factors and SSI, with intra-operative blood loss identified as a critical mediator. These findings underscore the importance of targeting modifiable perioperative risk factors to optimize surgical outcomes and inform early intervention strategies by elucidating the mechanisms underlying SSI development.