EFFECT OF ANTIBIOTIC-PROPHYLAXIS IN SURGE RY AND TIMING OF ADMINISTRATION ON THE RISK OF INFECTION OF THE SURGICAL-WOUND

Background. Clinical trials have demonstrated the efficacy of surgical prophylaxis (SP). Nevertheless, how the timing of antibiotic administ ration influences the risk of infection in clinical praxis has scarcel y been studied. In this study an assessment was made of whether the no n administration of antibiotic, or its administration longer than 2 ho urs preoperatively, or only postoperatively, are associated with a hig her rate of infection of the surgical wound (SWI) compared with antibi otic administration within the two hours prior to surgery in our setti ng. Methods. Observational, longitudinal, pseudo-retrospective study. It included 2,483 patients undergoing surgery in 1992, with clean-cont aminated, contaminated and dean with prophylaxis indication, and witho ut previous infection surgeries. Information on variables potentially associated with SWI and incidence of infection was monitored. A multiv ariate analysis was made by means of the logistic regression method to evaluate the association of prophylaxis and time of administration, c ontrolling for the remaining variables. Results. 754 patients received appropriate prophylaxis (within 2 hours prior to surgery); 28 of thes e patients (3.7%) developed SWI. Twenty-four of the 107 who received p rophylaxis longer than 2 hours prior to surgery developed infection (2 2.4%; p<0.001 compared with the first group; OD: 7.5, 95% CI: 3.94-14. 1); in the group of patients non receiving preintervention doses 94 pa tients developed infection (7.7%; p=0.001; OR: 2.16, 95% IC: 1.38-3.41 ). Among patients who did not receive prophylaxis 24 infections were d etected 16%; p=0.10; OR: 1.66, 95% CI: 0.91-2.99). In the multivariate analysis the administration of prophylaxis longer than 2 hours prior to surgery or postoperatively was confirmed to be associated with a hi gher SWI rate, as in the non-administration situation, controlling for the remaining variables (OR for longer than 2 hours: 5.82; for postop erative administration: 3.23, and for non-administration: 2.68). Concl usions. The administration of SP is inappropriate in a high percentage of cases. The administration of SP within the 2 hours prior to surger y reduces the risk of SWI, compared with the administration 2 hours or longer prior to intervention or only postoperatively.