Double-blind randomized placebo-controlled trial of the effect of ketamine on postoperative morphine consumption in children following appendicectomy

Background: Ketamine has an opioid sparing effect following surgery in adults. This study investigated whether a similar effect is seen following appendicectomy in paediatric patients. Methods: Seventy-five ASA 1 or 2 children aged 7-16 years were recruited, and randomly allocated to one of three groups. Following a standard anaesthetic for appendicectomy, all were prescribed patient controlled analgesia (PCA) morphine with paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDS) as required for postoperative analgesia. In addition the control group received a saline infusion postoperatively, the ketamine bolus group received 500 mug.kg(-1) intravenous (i.v.) ketamine preincision and a saline infusion postoperatively, and the ketamine infusion group received 500 mug.kg(-1) i.v. ketamine preincision and a ketamine infusion at 4 mug.kg(-1) min(-1) postoperatively. Morphine consumption, rescue analgesia requirement and side-effects were recorded postoperatively. Results: There was no difference in morphine consumption between the groups. The ketamine infusion group required more doses of rescue analgesia and reported more side-effects than the control group. Five patients, all in the ketamine infusion group, reported hallucinations. Conclusions: In this paediatric population intravenous ketamine did not have a morphine sparing effect. The increased incidence of side-effects, especially hallucinations, reported by patients given a ketamine infusion may limit the further use of postoperative ketamine in children.