[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: patient-controlled analgesia PCA is a rapidly spreading approach to the management of post-operative pain. The suitability of this method for the morbidly obese patient undergoing bariatric surgery has not yet been determined. METHODS: in the present study we randomly compared two groups of patients undergoing silastic ring vertical gastroplasty. One group received PCA (12 patients) and the other (11 patients) received intermittent doses of pethidine intramuscularly. RESULTS: the cumulative morphine use during the first post-operative day was 52.71 +/- 1.83 mg by the PCA group and an equivalent of 24.55 +/- 3.42 mg morphine by the IM pethidine group (p = 0.0002). The analgesic and sedative effects by the PCA were found to be superior. There were no significant differences between the groups in the incidence of side-effects or complications, except a higher, unexplained incidence of wound infection in the PCA group. CONCLUSION: use of PCA in patients undergoing bariatric surgery has obvious advantages and appears to be a safe procedure.