Epidural anaesthesia and postoperative colorectal motility--a possible hazard to a colorectal anastomosis

The effects of epidural anaesthesia (EDA, mepivacaine) and EDA in combination with atropine and neostigmine on postoperative intestinal motility were studied in 17 patients undergoing operation for cancer of the rectum or sigmoid colon. Motility was recorded by a volumetric technique. Epidural anaesthesia (EDA) increased motor activity in the small bowel as well as in the left colon and rectum. Phasic motility dominated in the small intestine whereas tonic and segmental contractions were recorded from the large bowel. EDA induced a powerful tonic contraction with a concomitant shortening of the rectum. This effect was inhibited by atropine. The influence of atropine/neostigmine on left colonic motor activity was studied in six patients before and during EDA in a cross-over fashion. When administered alone, atropine/neostigmine did not cause any motility increase. Atropine/neostigmine administered during EDA, however, elicited a significant increase of motility. The increase of intestinal motor activity induced by EDA may expose a newly constructed colorectal anastomosis to undue strain in the immediate postoperative period. When EDA is used in combination with general anaesthesia, particular attention should be directed towards the use of neostigmine for reversing the effect of nondepolarizing muscle relaxants. Atropine appears under such circumstances not to protect from the excitatory effects of this drug on colorectal motility.