Degree and extension of analgesic effect of morphine applied at three different spinal levels of epidural space

: Forty-five patients undergoing total abdominal hysterectomy were randomly divided into three groups. An epidural tube was inserted into one of the following three sites, Th11-12, L2-3, and caudal region. General anesthesia was then maintained with nitrous oxide-oxygen-enflurane, and pancuronium bromide. Morphine hydrochloride 2 mg in 8 ml of normal saline was administered into one of the designated epidural spaces one to two hours before the assumed end of surgery. Postoperative pain was assessed every four hours after the end of the operation until the next morning. Morphine exerted a relatively profound and prolonged analgesic effect in 40% of the Th11-12 group of patients, as well as in 6.7% of the L2-3 and caudal groups. But, supplementary analgesics were necessary in the other patients. No significant differences were found in the degree and extension of postoperative pain, as well as the doses of supplementary analgesics among the three groups. Adverse effects, such as nausea, vomiting and itching, occurred in 30 to 40% of each of the morphine administered groups. Though morphine was applied into different spinal levels, this clinical study did not show any difference in extension of analgesia. The epidurally applied morphine may be distributed widely in the spinal arachnoid space after some time, and may exert an effect on the brain as well as on the spinal nerves. When morphine is administered epidurally one to two hours before the end of a surgical operation, selection of an injection site according to the dermatome level of the skin incision may be unnecessary.