Subarachnoid morphine and fentanyl for labor analgesia. Efficacy and adverse effects.

BACKGROUND AND OBJECTIVES

The study was designed to compare analgesic efficacy and associated adverse effects between a group of parturients receiving subarachnoid opioids via the combined spinal-epidural (CSE) technique with a group receiving epidural analgesia alone for labor.

METHODS

The authors studied 59 healthy parturients admitted for labor and delivery. Group 1 consisted of 26 consecutive patients who received the CSE technique, initially receiving subarachnoid morphine sulfate 0.25 mg, and fentanyl 25 micrograms, for labor analgesia. If patients requested additional analgesia, epidural analgesia was initiated. Group 2 was comprised of 33 consecutive patients who received conventional epidural analgesia. All patients were monitored for the occurrence and treatment of peripartum nausea and vomiting (N/V), pruritus, postdural puncture headache, and respiratory depression.

RESULTS

Additional analgesia was requested by 20/26 (76%) patients in group 1. Group 1 reported more N/V (50% versus 15%, P = .01) and required more therapy for N/V (31% versus 0%, P < .01) than group 2. Furthermore, group 1 reported having more pruritus (50% versus 3%, P < .01), and required more treatment for pruritus (35% versus 3%, P < .01), than group 2. No patient developed significant respiratory depression. Only one patient in group 1 developed a postdural puncture headache, following unintentional dural puncture with the 18 gauge Tuohy needle.

CONCLUSIONS

The combination of subarachnoid morphine 0.25 mg and fentanyl 25 micrograms, when used for labor analgesia as part of the CSE technique, was associated with a higher incidence of clinically significant nausea and vomiting and pruritus, compared to conventional epidural anesthesia. Furthermore, the combination of subarachnoid morphine and fentanyl proved ineffective in providing adequate pain relief for the duration of labor and delivery for the majority of patients. The authors recommend that subarachnoid morphine and fentanyl serve a limited role in the treatment of labor pain.