Automated intermittent epidural boluses improve analgesia induced by intrathecal fentanyl during labour

Abstract

Purpose: We compared the efficacy of epidural continual intermittent boluses (CIB) with a continuous epidural infusion (CEI) in prolonging labour analgesia induced by the combined spinal epidural (CSE) technique.

Methods: CSE was instituted in 42 nulliparous parturients at the L3 to 4 level with intrathecal (IT) fentanyl 25 micro g followed by an epidural test dose of 3 mL of 1.5% lidocaine. These parturients were then randomly assigned to receive either epidural CIB (n = 21) or CEI (n = 21) with 0.1% ropivacaine and fentanyl 2 micro g x mL(-1). For the CIB, 5 mL boluses were given hourly, with the first bolus 30 min postinduction. CEI at the rate of 5 mL.hr(-1) was initiated in the minute after CSE. The duration of analgesia, pain score, degree of sensorimotor block were compared.

Results: From Kaplan Meier survival analysis, the duration of analgesia was significantly longer in CIB (mean survival time 239 +/- SD 24 min vs 181 +/- 17, P < 0.05 using log rank test). During the first three hours postblock, the median sensory block to cold was higher in CIB (P < 0.05, Mann U Whitney test) but no difference in blood pressure was detected [P > 0.05, repeated measure analysis of variance (RMANOVA)]. The serial pain scores were lower in the CIB (P < 0.05, RMANOVA).

Conclusion: CIB prolonged the duration and improved the quality of analgesia. CIB could have resulted in an improved spread of analgesics in the epidural space or encouraged a direct passage of infusate into the IT space. This could have also rendered a higher sensory block to cold in the CIB group. CIB is a good alternative to CEI for the maintenance of epidural analgesia after CSE.