Continuous high thoracic epidural administration of morphine with bupivacaine after thoracotomy.

Background And Objectives: The purpose of the study is to determine the ideal concentration of morphine when given with bupivacaine as a continuous high thoracic epidural infusion for postthoracotomy pain.

Methods: In a prospective study, 60 patients scheduled for thoracic surgery received a high thoracic epidural catheter. Postoperative analgesia was provided by a continuous epidural infusion for 3 days. The patients were randomly divided into two groups: group 1 (loading dose 1 mg morphine epidurally and continuous infusion of bupivacaine 0.75% + 0.2 mg/mL morphine at an infusion rate of 0.8 mL/hr); group 2 (loading dose 0.5 mg morphine epidurally and continuous infusion of bupivacaine 0.75% + 0.1 mg/mL morphine at an infusion rate of 0.8 mL/hr).

Results: The visual analog scales were not different at rest but with exercise in group 1 there was better pain relief than in group 2. The number of patients requiring supplementation of analgesia in group 2 (n = 42) was six times that of group 1 (n = 7). PaCO2 increased in both groups during the first postoperative day. There was no difference in the incidence of side effects between the two groups.

Conclusions: Continuous high thoracic epidural administration 0.2 mg/mL morphine in bupivacaine 0.75% at an infusion rate of 0.8 mL/hr with a loading dose of 1 mg morphine is an effective dose for postthoracotomy pain relief in rest, and more important, during exercise.