Antimicrobial prophylaxis for abdominal surgery: is there a need for metronidazole?

The objective of the present multicenter observational study was to assess postoperative infections as a function of risk factors and antibiotic prophylaxis under everyday clinical conditions. 2513 patients from 114 centers in Germany who received infection prophylaxis prior to elective colonic resection were included in the study between 1st September 1996 and 30th September 1997. In the descriptive analysis of the study it was noted that 36.1% of the patients had received no prophylaxis with metronidazole despite the fact that the study protocol recommended the use of this drug in preoperative antibiotic combinations. The present analysis therefore considers the influence of metronidazole on the postoperative infection rate. To exclude any bias due to intergroup differences in risk profile, the groups with and without metronidazole were subjected to a matched-pair analysis. Matching parameters were: duration of operation, blood loss, age, diabetes mellitus, hepatic, renal, or chronic airways disease, immunosuppressive therapy, and rectal resection. This led to the formation of 800 pairs that were matched with respect to these parameters. The 800 pairs were then stratified into the following treatment groups: Group 1: long-acting cephalosporin (ceftriaxone) with or without metronidazole (n = 2 x 491); Group 2: short-acting cephalosporins with or without metronidazole (n = 2 x 133); Group 3: broad-spectrum penicillins with or without metronidazole (n = 2 x 176). In all three treatment groups combination therapy with metronidazole was found to be significantly superior. Postoperative infection rates with and without metronidazole were 9.4% and 18.7% respectively in Group 1, 12.0% and 25.6% respectively in Group 2, and 19.9% and 29.0% respectively in Group 3. The lowest infection rate was thus achieved by means of preoperative infection prophylaxis with ceftriaxone plus metronidazole. Thus, preoperative administration of metronidazole in addition to a long-acting beta-lactam antibiotic is strongly advised in elective colon surgery, as absence of antibiotic cover against anaerobic colonic flora leads to a significantly higher postoperative infection rate.