Impact of bodyweight-adjusted antimicrobial prophylaxis on surgical-site infection rates.

Background: Antimicrobial prophylaxis (AMP) adjustment according to bodyweight to prevent surgical-site infections (SSI) is controversial. The impact of weight-adjusted AMP dosing on SSI rates was investigated here.

Methods: Results from a first study of patients undergoing visceral, vascular or trauma operations, and receiving standard AMP, enabled retrospective evaluation of the impact of bodyweight and BMI on SSI rates, and identification of patients eligible for weight-adjusted AMP. In a subsequent observational prospective study, patients weighing at least 80 kg were assigned to receive double-dose AMP. Risk factors for SSI, including ASA classification, duration and type of surgery, wound class, diabetes, weight in kilograms, BMI, age, and AMP dose, were evaluated in multivariable analysis.

Results: In the first study (3508 patients), bodyweight and BMI significantly correlated with higher rates of all SSI subclasses (both P < 0.001). An 80-kg cut-off identified patients receiving single-dose AMP who were at higher risk of SSI. In the prospective study (2161 patients), 546 patients weighing 80 kg or more who received only single-dose AMP had higher rates of all SSI types than a group of 1615 who received double-dose AMP (odds ratio (OR) 4.40, 95 per cent c.i. 3.18 to 6.23; P < 0.001). In multivariable analysis including 5021 patients from both cohorts, bodyweight (OR 1.01, 1.00 to 1.02; P = 0.008), BMI (OR 1.01, 1.00 to 1.02; P = 0.007) and double-dose AMP (OR 0.33, 0.23 to 0.46; P < 0.001) among other variables were independently associated with SSI rates.

Conclusion: Double-dose AMP decreases SSI rates in patients weighing 80 kg or more.