A total of 147 RCTs (n=23,049) were included in the review.
The methodological quality of the included trials improved over time, but problems concerning randomisation, blinding and insufficient sample size remained.
Antibiotic prophylaxis significantly reduced the rate of SWI in comparison with no antibiotic (4 trials, n=293). The OR was 0.24 (95% CI: 0.13, 0.43).
The overall rate of SWI with various regimens of prophylactic antimicrobial agents in colorectal surgery across all the included studies was 11.1% (2,540 out of 22,927). It was 10.6% for the 120 trials in elective surgery only, and 13.4% for the 27 trials in both elective and emergency surgery patients.
In general, the efficacy of many different regimens appeared to be similar. However, many trials were too small to demonstrate a difference between treatments if one had existed. Some regimens appeared to be less effective, such as metronidazole, doxycycline, and piperacillin monotherapies. There was insufficient evidence to determine the relative efficacy of different routes of administration.
A meta-analysis of 17 studies that compared a single dose with multiple doses of the same antibiotic, or combination of antibiotics, showed no significant difference in SWI (OR 1.17, 95% CI: 0.89, 1.54). There was insufficient evidence to draw conclusions about single- versus multiple-dose prophylaxis in relation to the duration of the surgical operation.
A meta-analysis of 6 trials that compared a first-generation cephalosporin with a second- or third-generation cephalosporin showed no significant difference in SWI (OR 0.93, 95% CI: 0.46, 1.86).
Other efficacy outcomes were reported inconsistently in the trials and may, therefore, be influenced by detection and reporting bias. Results of these outcomes were provided in the report.
Seventy-four of 134 trials published in English reported adverse events. Patients with a history of allergy to drugs were not included in these trials. Commonly reported adverse events included skin rash, nausea and diarrhoea. Only one trial reported serious adverse events, namely post-operative bleeding in patients treated with latamoxef.