Intrathecal morphine in orthopaedic surgery patients. Optimised dose in patients receiving dipyrone

INTRODUCTION: The influence of different postoperative doses of intrathecal morphine on the time of first opioid request by orthopaedic patients was investigated. The first choice analgesic was dipyrone and a maximum dose of 6 mg/day was allowed. METHODS: A prospective, double-blind, placebo-controlled, clinical trial was conducted with 15 patients in each group receiving intrathecally either a placebo, 0.05 mg morphine, 0.1 mg morphine or 0.2 mg morphine in combination with a spinal anaesthesia with isobaric bupivacaine. RESULTS: The number of patients without opioid requirement during the first 24 h after surgery were 3, 8, 14 and 14 in the placebo group and after 0.05 mg (p=0.128), 0.1 mg (p=0.0001) and 0.2 mg (p=0.0001) intrathecal morphine, respectively. The average time until first opioid requirement increased in a dose-dependent manner from 10.3 h to 23.9 h (p<0.0001). CONCLUSION: In orthopaedic patients with dipyrone as the primary analgesic, the addition of 0.1 mg or 0.2 mg morphine to spinal anaesthesia provided a simple long-lasting postoperative analgesia and the use of additional opioids could be avoided during the 24h postoperative period.