Perioperative Intravenous Antibiotic Regimens and Surgical Site Infection After Colorectal Surgery: Clinical Associations and External Evaluation of Risk Prediction Models

Background/Objectives: Surgical site infection (SSI) remains a major complication after colorectal surgery. Comparative evidence for commonly used perioperative intravenous antibiotic regimens is limited, and risk prediction models require external evaluation before clinical use. We examined regimen–SSI associations and secondarily evaluated models using routine perioperative variables to distinguish patients with and without electronically recorded postoperative SSI.

Methods

We analysed 732 adults from MIMIC-IV for regimen association and model development and 133 adults from ICU-based eICU-CRD for external model evaluation. SSI was identified using an electronic phenotype. Four intravenous antibiotic exposure groups were compared using multivariable logistic regression and exploratory interaction analyses. Predictors selected using LASSO screening followed by clinical refinement informed six models, which were assessed using discrimination, calibration, and classification metrics.