Bowel function after bowel surgery: morphine with ketamine or placebo; a randomized controlled trial pilot study

Background: Morphine decreases gut peristalsis, and ketamine decreases morphine use after surgery, and does not slow peristalsis. Thus, the combination should result in faster return of bowel function after surgery than morphine alone. Methods: A double-blind randomized controlled trial of saline vs. ketamine with intravenous patient-controlled-analgesia morphine for post-operative pain control was conducted on 42 patients having bowel resection. Bowel function was assessed by auscultation, time to passage of flatus and stool, and time to first retained oral intake; pain by visual analog scale. Time to return of all four measures of bowel function was the primary outcome. Results: Despite a ketamine dose that in other studies had decreased morphine use without side-effects, there was no difference in bowel function, pain control, or morphine use between the two groups. Ketamine resulted in hallucinations in six out of 19 patients, with none in the placebo group (P =0.018). Conclusion: Low-dose ketamine was not efficacious for hastening return of bowel function, or for decreasing post-operative pain after surgery for bowel resection. It resulted in hallucinations in some patients. Those reporting hallucinations all wished to remain in the study.