RESUMO
BACKGROUND: The traditional National Healthcare Safety Network (previously National Nosocomial Infections Surveillance) risk index is used to predict the risk of surgical site infection across many operative procedures. However, this index may be too simple to predict risk in the various procedures performed in colorectal surgery. The aim of this study was to evaluate the usefulness of the risk index by analyzing the impact of the risk index factors on surgical site infection after abdominal colorectal surgery. METHODS: Using our surgical site infection surveillance database, we analyzed retrospectively 538 consecutive patients who underwent abdominal colorectal surgery between 2005 and 2010. Correlations between surgical site infection and the following risk index factors were analyzed: length of operation, American Society of Anesthesiologists score, wound classification, and use of laparoscopy. The 75th percentile for length of operation was determined separately for open and laparoscopic surgery in the study model. RESULTS: Univariate analyses showed that surgical site infection was more strongly associated with a >75th percentile length of operation in the study model (odds ratio [OR], 2.07) than in the traditional risk index model (OR, 1.64). Multivariable analysis found that surgical site infection was independently associated with a >75th percentile length of operation in the study model (OR, 2.75; 95% confidence interval [CI], 1.66-4.55), American Society of Anesthesiologists score ≥3 (OR, 2.22; 95% CI, 1.10-4.34), wound classification ≥III (OR, 5.29; 95% CI, 2.62-10.69), and open surgery (OR, 2.21; 95% CI, 1.07-5.17). Performance of the risk index category was improved in the study model compared with the traditional model. CONCLUSIONS: The risk index category is sufficiently useful for predicting the risk of surgical site infection after abdominal colorectal surgery. However, the 75th percentile length of operation should be set separately for open and laparoscopic surgery.