Pre-operative antibiotics and elective colonic resections: Do they reduce surgical site infection and anastomotic leak rates?

Background: Surgical site infections (SSI) and anastomotic leaks (AL) are a significant source of morbidity in patients undergoing elective colorectal surgery. There is evidence for use of pre-operative oral antibiotics (OAB), in combination with mechanical bowel preparation (MBP), to reduce SSI and AL rates in this population. We aimed to determine whether the use of OAB pre-operatively reduced our local SSI rate in elective left-sided colonic resections.

Methods: A pre-post intervention study was conducted in a large regional hospital from September 2018 to July 2019. Following approval by the Trust’s Medicines Optimisation Group, patients received oral metronidazole 400mg and oral neomycin 1g at 06:00, 14:00 and 22:00 on the day before surgery. The rates of SSI and AL at 30 days were compared with pre-intervention patients. Standard induction intravenous antibiotics were given to both groups but MBP practices were disparate among the consultant body and were outside the scope of this project. Chi Square and Independent T-tests were used to analyse the data.

Results: Data on 100 pre-intervention patients and 47 post-intervention patients showed similar baseline characteristics. SSI rates were 17% (17/100) in the pre-intervention group and 8.5% (4/47) in the post-intervention group (p=0.170). Anastomotic leak rates were 7.0% (7/100) and 2.1% (1/47) respectively (p=0.225).

Conclusion: The use of pre-operative OAB was associated with a reduction in SSI and anastomotic leak rates, although these did not reach statistical significance. Possible reasons for this include low patient numbers and inconsistent use of MBP.