Dose minimization study of single-dose epidural morphine in patients undergoing hip surgery under regional anesthesia...

In order to decrease the rate of adverse effects, we aimed to identify the lowest analgesic dose of epidural morphine administered to patients undergoing hip surgery.

Forty-five ASA I-II children undergoing surgical correction of hip dysplasia under caudal or epidural anesthesia with bupivacaine were randomized to receive epidural morphine 11.2, 15 or 20 microg.kg(-1) (groups 1, 2 and 3, respectively; 15 patients per group) immediately after completion of surgery. Postoperative pain control, sedation, motor block, urinary retention, pruritus and vomiting were evaluated.

In the recovery room, 46.7% of patients from group 1, 33.3% from group 2, and 93.3% from group 3 were sleeping but were easy to arouse (x(2) = 12.2; P < 0.005). The rest of the patients from each respective group were completely asleep. The cardiovascular and respiratory parameters were within normal limits. The ability to move the legs returned approximately 1 h after surgery in all three groups. Seven patients (46.7%) from group 1, nine (60%) from group 2, and 13 patients (86.7%) from group 3 vomited (x(2) = 5.4; P = 0.06). One patient receiving 20 microg.kg(-1) morphine experienced urinary retention. One patient receiving 15 microg.kg(-1) morphine suffered from pruritus. The duration of analgesia was similar, 12-14 h, in all three groups.

In patients undergoing hip surgery under regional anesthesia with bupivacaine, epidural morphine at a dose of 11.2 microg.kg(-1) administered immediately after completion of the procedure resulted in adequate pain relief for more than 12 h. Explanation of the high rate of patients vomiting (>45%) remains to be elucidated.