A comparison of epidural and intramuscular morphine in patients following cesarean section

This randomized, double-blind study compared epidural (EP) and intramuscular (IM) morphine in 24 healthy parturients for 24 h after cesarean section. The 11 EP subjects received 5 mg of EP morphine and normal saline intramuscularly, and the 13 IM patients received 5 mg of IM morphine and normal saline epidurally. Both injections were given simultaneously just after delivery and then upon request with at least 30 min between each pair of injections. Blood pressure, visual analogue scale pain score, somnolence score, and presence of nausea, vomiting, or pruritus were assessed every 30 min for 1 h after each dose and then hourly. Oxyhemoglobin saturation (Spo2) and respiratory rate (RR) and pattern were monitored continuously with pulse oximetry and respiratory inductive plethysmography. The EP group had significantly lower pain scores (less pain) than the IM (0.9 +/- 0.3 vs. 3.3 +/- 1.3; mean +/- SD; P less than 0.001) with less morphine (0.3 +/- 0.2 vs. 2.2 +/- 0.6 mg patient-1 h-1; P less than 0.001). There was no difference between groups for RR, Spo2, incidence or frequency of slow respiratory rate (SRR, 5-min mean RR less than 10) and apneas (AP, greater than or equal to 15 s of less than 100 ml tidal volume), incidence of nausea and/or vomiting, pruritus, or hypotension, and hours asleep or drowsy. There were no major respiratory abnormalities. During control monitoring of nine EP and 11 IM subjects while asleep postoperatively, the RR, Spo2, and incidence and frequency of SRR and AP were similar to the study period in both groups. In conclusion, EP morphine was a more effective analgesic than IM morphine, but the side effects of both were similar.