Antibiotics in elective colon surgery. A randomized trial of oral, systemic, and oral/systemic antibiotics for prophylaxis. Oral versus systemic antibiotic prophylaxis in elective colon surgery: a randomized study and meta-analysis send a message from the 1990s. Comparison between oral and systemic antibiotics and their combined use for the prevention of complications in colorectal surgery. Failure of topically applied antibiotics, added to systemic prophylaxis, to reduce perineal wound infection in abdominoperineal excision of the rectum.
A prospective, randomized double-blind study was undertaken to compare the efficacy of three prophylactic regimens (oral neomycin and erythromycin, intravenous cefoxitin, and a combination of both oral and intravenous antibiotics) in patients undergoing elective colorectal surgery. One hundred sixty-nine patients were randomized and 146 patients were evaluable. Septic complications occurred in 11.4 per cent of patients receiving oral antibiotics only, in 11.7 per cent of patients receiving intravenous cefoxitin alone, and in 7.8 per cent of patients receiving both oral and intravenous antibiotics. These differences were not statistically different. The greatest number of septic complications occurred in those patients with anastomotic disruptions. Two patients died (1.3%), both of whom had major anastomotic failures. There was no advantage between any of the groups in the incidence of wound infection (3.9-6.8%). Thus, no advantage could be identified in this study in the combination of oral and intravenous antibiotics in elective colorectal surgery. To compare the efficacy of combined oral and systemic antibiotics (combined) versus systemic antibiotics (systemic) alone in preventing surgical site infection in elective surgery of the colon, and to perform a meta-analysis of randomized studies comparing combined versus systemic antibiotics in elective colon surgery.
                A double-blind, placebo-controlled, randomized clinical trial.
                The Queen Elizabeth Hospital, Montreal, a university-affiliated community hospital.
                Two hundred and fifteen patients scheduled to undergo elective surgery of the colon.
                Patients were randomized to receive neomycin and metronidazole orally (109 patients) or identical placebos (106 patients) on the final preoperative day. All were given amikacin and metronidazole intravenously just before operation. Thirteen randomized series comparing combined and systemic antibiotic prophylaxis in elective colon surgery were identified for meta-analysis.
                Rates of postoperative surgical site infections: risk differences, risk ratios (RRs) and 95% confidence intervals (CIs); organisms found in the colon and wound fat at surgery, and in infected wounds.
                Three patients in the systemic group, and 5 in the combined group were excluded. Wound infections occurred in 5 patients in the combined group but in 17 in the systemic group (p < 0.01, RR = 0.29, 95% CI 0.11-0.75). Bacteria isolated from wound infections and wound fat were similar to those found in the colon. They were more frequent in the colon in the systemic group (p < 0.001) and occurred in wound fat in the systemic group twice as often as in the combined group (p < 0.001). By stepwise logistic regression, the presence of bacteria in wound fat at surgery was the strongest predictor of postoperative wound infection (p < 0.002). In the meta-analysis, the summary weighted risk difference in surgical site infections between groups (d(w)) and the summary RR both favoured combined prophylaxis (d(w) = 0.56, 95% CI 0.26-0.86; RR = 0.51, 95% CI 0.24-0.78; p < 0.001).
                In elective surgery of the colon combined oral and systemic antibiotics are superior to systemic antibiotics in preventing surgical site infections. Orally administered antibiotics add value by reducing bacterial loading of the colon and wound fat contamination, both associated with postoperative wound infection. Meta-analysis of randomized clinical trials reported from 1975 to 1995 supports these conclusions. Ninety patients were included in this prospective randomized trial. Each required electric colorectal surgery and was prepared for operation with oral preoperative antibiotic therapy, systemic peroperative therapy, or by a combination of both. The number of each type of septic postoperative complication and their total did not differ between the group treated by oral antibiotics prior to operation and the group treated peroperatively with systemic antibiotic therapy. The total number of septic complications (wall abscesses, fistulas, subdiaphragmatic abscesses, septicemia, peritonitis), however, was significantly less (P less than 0.05) in the group treated by both preoperative oral antibiotics and peroperative systemic antibiotic therapy (3.3 per cent) than in either groups treated only orally preoperatively (30 per cent) or by systemic antibiotic therapy during the operation (23 per cent). The combination of oral antibiotic therapy prior to operation and of systemic peroperative antibiotic therapy, therefore, presents the most effective prophylactic effectiveness. In a prospective, randomized trial, prophylactic use of topical antibiotics in addition to systemic prophylaxis was studied in patients undergoing abdominoperineal amputation of the rectum. All patients received gentamicin 80 mg and metronidazole 500 mg intravenously at induction of anesthesia, followed by the same dose 8 hourly for 48 hours. In accordance with the randomization, half of the patients were additionally given gentamicin 160 mg + metronidazole 400 mg topically into the perineal wound at closure. Perineal wound infection appeared in 19 of the 41 patients who received both systemic and topical prophylaxis, and in 18 of the 38 with only systemic antibiotics. Cell-mediated immunity was preoperatively assessed with a skin test (Multitest) in all but three patients. Impairment of cell-mediated immunity was associated with significantly heightened rate of wound infection, and these patients did not benefit from topical antibiotics.
The authors of this review have been unable to identify the most effective intervention or to assess the associated risks. Research is urgently needed into the effectiveness of oral versus topical antibiotics in this group of patients. Clinicians considering antibiotic treatment need to balance any potential benefit against the risks of side effects and antibiotic resistance.