INTRATHECAL ADMINISTRATION OF HYPERBARIC MORPHINE FOR THE RELIEF OF PAIN IN LABOR

Healthy women (30) in active labor received an intrathecal injection of morphine 0.5 mg (n = 12) or 1 mg (n = 18) in 7.5% dextrose. Both doses provided excellent analgesia for labor, 93% of patients obtaining at least 50% pain relief. Analgesia began 15-60 min after injection and did not decrease until 6-8 h after injection. Analgesia was satisfactory until distension of the perineum, either by forceps or the infant''s head. The intrathecal injection of morphine did not adversely affect the condition of the infant. Eighty percent of patients developed pruritus; 53%, nausea or vomiting, or both; 43%, urinary retention; and 43%, drowsiness. These side effects were decreased by naloxone, which did not affect the degree of analgesia. There was no significant depression of ventilation in any patients. Evidently morphine 0.5 or 1 mg, administered intrathecally, effectively decreases the pain of labor, and i.v. administration of naloxone can alleviate the common side effects.