Intrathecal morphine in cardiac surgery

The effects of intrathecal morphine in 60 patients undergoing open-heart surgery were studied in an observer-blind control trial. The patients were randomly allocated into three groups of 20 each: (A) Control, (B) 2 mg and (C) 4 mg of intrathecal morphine. This study confirms that intrathecal morphine provides useful post-operative analgesia. Patients given intrathecal morphine required less postoperative analgesia and sedation and their respiratory function tests were less depressed than the control group. Since the completion of this study, reports have suggested that 1 mg of morphine intrathecally avoids the serious complications of respiratory depression. In the study described, the patients were electively ventilated post-operatively and respiratory depression was therefore not a problem. Of the other associated side-effects of intrathecal morphine, vomiting (20%) and pruritus (20%) proved the most troublesome.