Epidural Morphine for Postoperative Pain: Experience with 1085 Patients

Abstract

A prospective study of the effect and side-effects of epidural morphine for pain relief in 1085 patients after thoracic, abdominal, urologic or orthopedic surgery was performed. Morphine chloride was diluted in saline or bupivacaine and administered through an epidural catheter placed at a segmental level appropriate for the type of surgery. The initial dose was 4 or 6 mg morphine and supplementary doses were given when needed to obtain complete freedom from pain during deep breathing or nursing care. The total dose of epidural morphine from end of surgery until the next morning varied from 4-18 mg. Ninety-seven percent of hip arthroplasty patients, 91% of prostatectomy patients and thoracotomy patients, 90% of patients after major lower extremity surgery and 88% of patients after laparotomy were completely satisfied with the postoperative course. For hip arthroplasty and major extremity surgery, an initial dose of 4 mg of epidural morphine was as effective as 6 mg. After prostatectomy, laparotomy, and thoracotomy, an initial dose of 6 mg gave significantly better effect than 4 mg. Pruritus occurred in 11%, nausea or vomiting in 34%, and respiratory depression in 0.9% of the total patient population. Urinary retention occurred in 42% of patients not having urinary catheters in place. Postoperative nausea or vomiting was more frequent in women than in men (P < 0.001). There was a higher incidence of nausea or vomiting in men experiencing pain than in men who were completely pain-free after abdominal surgery (P < 0.001). Respiratory depression was rare and occurred as a gradually decreasing respiratory rate. Treatment with naloxone was effective without pain-breakthrough. Naloxone relieved pruritus in 90% of patients in whom it was attempted, but was not effective in treating nausea, vomiting or urinary retention. After this study the recommended dosage regimen for postoperative epidural morphine is: for major surgery of the lower limb or hip arthroplasty 4 mg; after prostatectomy, laparotomy, and thoracotomy 6 mg. No later than 12 h before the patients leave the postoperative care unit, 1/2 the initial dose of epidural morphine is usually repeated. Morphine is diluted in bupivacaine if pain is already present, otherwise in saline.