Surgical wound infections diagnosed after discharge from hospital: epidemiologic differences with in-hospital...

The purpose of this study was to study postoperative infections detected in hospital and after discharge and to identify risk factors for such infections.

A prospective cohort study was used, with follow-up of 30 days after hospital discharge, on 1483 patients admitted to the general surgery service of a tertiary care hospital. The main outcome measure was surgical wound infection (SWI). Relative risks, crude and multiple risk factors adjusted for by logistic regression analysis, and their 95% confidence intervals (CIs) were estimated.

During follow-up 155 patients showed evidence of nosocomial infection, 134 in hospital and 21 at home, yielding a cumulative incidence of 10.5%. According to several variables (age, American Society of Anesthesiologists score, serum albumin, the SENIC and National Nosocomial Infections Surveillance indexes of intrinsic patient risk, length of hospital stay, etc.) there were no differences between patients with postdischarge SWI and uninfected patients; however, differences were detected between postdischarge SWI and in-hospital SWI, as well as between patients with in-hospital SWI and patients without infections. The analysis of risk factors showed that most predictors for in-hospital SWI did not behave in the same manner for postdischarge SWI. Stepwise logistic regression analysis identified cancer (odds ratio = 4.5, 95% CI = 1.7 to 12.2, p = 0.003) and surgeon performing the operation (for medium risk, OR = 4.4, 95% CI = 0.9 to 21.3, p = 0.059; for high risk, OR = 3.0, 95% CI = 0.7-13.3, p = 0.144) as independent risk factors for postdischarge SWI.

There were important epidemiologic differences between in-hospital SWI and postdischarge SWI; most risk factors for in-hospital SWI are not predictors for postdischarge SWI.