Interpreting the evidence for chlorhexidine wound irrigation in contaminated abdominal surgery

Kultanaruangnonth et al. recently reported a well-conducted double-blind randomized trial comparing intraoperative irrigation with 0.05% aqueous chlorhexidine gluconate (CHG) against normal saline for the prevention of surgical site infection (SSI) in abdominal surgery, concluding that CHG did not significantly reduce SSI. We raise three interpretive points. First, the antimicrobial rationale offered for CHG draws on clean-field trials (arthroplasty, caesarean delivery, breast reconstruction) in which SSI is driven by skin flora, whereas this trial's population was predominantly colorectal and hepatobiliary/contaminated surgery, fields dominated by enteric gram-negative and anaerobic organisms against which chlorhexidine is comparatively less active a plausible explanation for the smaller-than-expected effect. Second, the trial's own 95% confidence interval for the primary risk ratio (0.45-1.25) spans a 55% relative reduction to a 25% relative increase in SSI, and is compounded by a statistically fragile exploratory multivariable model (49 events across eight covariates, several dichotomized); we argue the result is more accurately described as statistically inconclusive than as a negative finding. Third, the Discussion's suggestion of particular benefit 'in high-risk populations' is not supported by any treatment-by-subgroup interaction analysis in the manuscript. We conclude that these findings argue for a larger, stratified, culture-informed confirmatory trial rather than for adopting or abandoning CHG wound irrigation in contaminated abdominal surgery.