Continuous Epidural Infusion of Morphine for Pain Relief After Cardiac Operations

Abstract

Postoperative pain relief and stress hormones were examined during the use of continuous epidural infusion of morphine at a rate of 0.1 mg/hr in 30 patients (Group B) after coronary artery bypass grafting. This was compared to our routine method of postoperative analgesia of intravenous morphine 2 mg/2 hr and as needed in another 30 patients (Group A). Continuous epidural morphine infusion required occasional supplementation with intravenous morphine and achieved effective analgesia in 80% of the patients. Pain relief was adequate in 50% of the patients in Group A. The mean dose of morphine used in Group B during the first 3 postoperative days was 5 mg per patient per day and was significantly lower than that used in Group A (mean 18 mg per patient per day). Serum morphine was undetectable (below 2.5 ng/ml) in Group B and was significantly lower than that in Group A (17 ng/ml). Epidural analgesia was associated with adequate postoperative pulmonary and cardiovascular functions; nausea and vomiting occurred in two patients. Levels of postoperative stress, serum cortisol, and beta-endorphin were significantly lower in Group B than in Group A. This study shows that continuous epidural infusion of morphine at a rate of 0.1 mg/hr provides selective and effective pain relief and reduces postoperative stress after cardiac operations. This method of analgesia was also associated with minimal side effects and provides an alternate approach for treatment of pain after cardiac operations.