Mini-Dose Intrathecal Morphine for the Relief of Post-Cesarean Section Pain

Abstract

Thirty-three healthy women at term were scheduled to receive spinal anesthesia with 0.75% bupivacaine in 8.25% dextrose. In a double-blind fashion, all patients also received an intrathecal addendum of 0.5 ml of saline alone or containing either 0.1 or 0.25 mg of preservative-free morphine. Employing a visual analog scale (no pain to worst pain possible) postoperative pain was assessed at 3,6,12,16 and 24 hours postoperatively. Simultaneous determinations of maternal respiratory rate, heart rate, blood pressure, nausea and vomiting, and pruritus were made. Possible respiratory depressant effects of morphine were assessed by determining the responses to progressive hypercapnia. When pain relief was needed within the first 24 postoperative hours, 8 mg of morphine were given SC, followed by CO2 response determinations at 1.5 and 3.0 hours after injection. Neonatal status was determined by Apgar scores at birth and NACS at 2 and 24 hours after birth.