Risk factors for prediction of surgical site infections in "clean surgery".

BACKGROUND: The aim of this study was to determine the risk factors of surgical site infections (SSI) in clean surgery and to identify high- and low-risk patients from whom efficacy of the antibiotic prophylaxis was analyzed.

METHODS: From June 1982 to September 1996, a database was established from 3 prospective multicenter randomized studies, containing information of 5798 patients who underwent abdominal noncolorectal surgery. Multivariate analysis was performed using nonconditional logistic regression expressed as an odds ratio (OR).

RESULTS: A total of 2374 patients underwent a clean surgery. An antibiotic prophylaxis was administered to 1943 patients (81.8%). A multivariate analysis was performed including only preoperative factors and disclosed 3 independent factors: cirrhosis (OR, 2.8; 95% CI: 1.6-12.8), other disease (OR, 2.7; 95% CI: 1.3-5.8), and preoperative urinary catheter (OR, 2.1; 95% CI: 1.1-4.6). A risk score for SSI was constructed: -4.9 + (1.5 x cirrhosis++) + (other disease++) + (0.8 x preoperative urinary catheter++) (++ = 0 if absent or 1 if present). The study included 1 group of patients having no risk factors for SSI with a score below -4.5 (S1R-) and 1 group of patients having 1 or more risk factors for SSI with a score over -4.5 (S1R+). Antibiotic prophylaxis did not reduce the infectious complication rate in the S1R- group, whereas, in the S1R+ group, it reduced significantly the rate of SSI and of parietal infectious complications by 58% and 69%, respectively.

CONCLUSIONS: Antibiotic prophylaxis in clean abdominal surgery was effective in high-risk patients. Urinary catheter must be avoided.