Intrathecal plain vs hyperbaric bupivacaine for labour analgesia: efficacy and side effects

Baricity is an important determinant of block characteristics of the spinal component of a combined spinal epidural (CSE) for labour analgesia. This study compares the analgesic efficacy and side effects of intrathecally administered plain and hyperbaric bupivacaine (both with fentanyl) during active labour.

Sixty-two women in active labour (cervical dilatation >or=5 cm and pain score > 5) were randomized in a prospective, single-blinded fashion to receive 2.5 mg of either hyperbaric or plain bupivacaine both combined with 15 microg of fentanyl as the spinal component of a CSE. The primary outcome was failure of satisfactory analgesia within ten minutes of the intrathecal injection as defined by a verbal pain score > 3. Secondary outcomes included need for rescue analgesia, hypotension, respiratory depression, nausea and vomiting, pruritus and sustained fetal bradycardia.

Sixty patients were analyzed. The failure rates were 20% in the hyperbaric group vs 0% in the plain group (P=0.024). The plain solution provided faster onset, higher sensory levels and less motor block at all times during the first 30 min. The incidence of both pruritus and sustained fetal bradycardia was 33% in the plain group and 10% in the hyperbaric group (P=0.03).

A plain rather than hyperbaric solution of bupivacaine 2.5 mg with fentanyl 15 microg provides a faster onset of analgesia, higher sensory levels and less motor block, while demonstrating an increased incidence of pruritus and sustained fetal bradycardia.