Abstract

Sixty-seven nonrandomized patients undergoing major hip surgery performed under spinal analgesia with bupivacaine and morphine (0.3 mg) were studied. The aims were to find a suitable dose regimen of naloxone that offered protection against respiratory depression without altering pain relief, and to measure plasma levels of naloxone and morphine for comparison with the clinical effects observed. The most beneficial regimen was found to be 1 μg/kg/hr given during the first 12 hours postoperatively and 0.25 μg/kg/hr during the next 12 hours. In comparison with higher doses (1-5 μg/kg/hr), pain relief was better. In comparison with a previous study, where no naloxone was given, pain relief was unaltered and resting ventilation was improved. There was no discernible relationship between the clinical effects observed and plasma concentrations of naloxone and morphine.