[Investigations on epidural morphine. Efficacy, solvent, analgesic supplementation]

The effects of epidural morphine for pain relief after orthopaedic surgery of the lower extremity were examined in 60 patients. Intraoperative analgesia was achieved with epidural administration of 2% mepivacaine. The patients were divided in a double-blind, random fashion into 3 groups. Group I received 2 mg morphine base (2.63 mg morphine hydrochloride) in 10 ml 0.9% sodium chloride, Group II received 2 mg morphine base in 10 ml 5% glucose, and Group III, 10 ml 5% glucose as placebo. The quality of analgesia was judged by 1) the amount of i.m. pentazocine (0.5-1 mg/kg) required during the first 24 h, and 2) the analysis of a visual analog scale. The duration of epidural morphine analgesia was 13 +/- 9.4 h. For supplementary postoperative analgesia, the patients in Group I required a mean dose of 24 mg, Group II 18 mg, and Group III 48 mg of pentazocine (P less than 0.001 and 0.05 respectively) within the first 12 h. The solution (glucose or normal saline) had no influence on morphine effectiveness. The side effects were urinary retention in 8 patients (20%) and pruritus in one (3%). It is concluded that 2 mg of morphine base administered epidurally is an effective method of postoperative pain relief in orthopaedic patients.