Satisfactory analgesia with minimal emesis in day surgeries: a randomised controlled trial of morphine versus hydromorphone

BACKGROUND: Opioids remain the mainstay therapy for post-surgical pain. Although both morphine and hydromorphone are potent analgesics, it has been suggested that hydromorphone is clinically better. Our primary objective was to compare morphine with hydromorphone for achieving satisfactory analgesia with minimal emesis (SAME). METHODS: We performed a multicentre RCT in 402 patients having ambulatory surgery. A random computer-generated allocation, stratified by site, was developed by our pharmacy. Concealment was achieved by allocating patients to study groups by nurses using sequentially coded study medication syringes having equi-analgesic doses, made available in the postoperative recovery room. Patients, health providers, and research personnel were blinded. The operating-room protocol allowed for routine anaesthetic management, excluding the use of study medications. Study medications were administered by recovery nurses as per an algorithm. Analyses utilised the intention-to-treat principle, and regression analyses were used for outcomes as appropriate and using multiple imputation. RESULTS: Of 751 patients, 402 were randomised between morphine (n=199) and hydromorphone (n=203). Baseline and intraoperative variables were comparable across the groups. The odds of achieving SAME were similar between the groups (odds ratio: 1.01; 95% confidence interval: 0.57-1.80). There were no differences in the side-effects of severe itching, respiratory depression, or sedation. Patient satisfaction, discharge times, and post-discharge outcomes, including pain and nausea/vomiting over 24 h, were also comparable. CONCLUSIONS: There was no difference between morphine and hydromorphone regarding analgesia and common side-effects. The appearance of dose-limiting side-effects is idiosyncratic; the clinical decision must be based on individual responses. CLINICAL TRIAL REGISTRATION: NCT02223377.