The respiratory depression of epidural morphine. Time course and effect of posture.

In order to investigate the time course of the late respiratory depression which has been reported following epidural opiates, the response to CO2 was measured in 11 patients. Epidural morphine 2 mg was given 1 hour after operation under bupivacaine epidural anaesthesia, and the patients nursed supine. The results show a consistent pattern of respiratory depression commencing at approximately 48 hours, and continuing until 18-24 hours after administration of morphine. A similar group of 10 patients nursed in a sitting position did not show the same degree of depression, and a modifying effect of posture on the development of central effects is suggested.