Epidural Volume Extension During Combined Spinal-Epidural Labor Analgesia Does Not Increase Sensory Block.

Background: Combined spinal-epidural (CSE) analgesia is widely used for delivering labor analgesia. Epidural volume extension (EVE) involves the injection of fluid into the epidural space compressing the dural sac, causing cephalad shift of the cerebral spinal fluid. Our hypothesis was that EVE with 10 mL normal saline during CSE would increase the sensory block height at 15 minutes after intrathecal injection. We expected EVE to decrease pain scores, decrease analgesia onset time, and decrease motor block compared with performing CSE without EVE (NEVE).

Methods: We randomly assigned 60 healthy term laboring nulliparous parturients with cervical dilation <5 cm to receive CSE either with EVE of 10 mL normal saline through the Tuohy needle before catheter insertion or CSE NEVE. Intrathecal analgesia consisted of 2 mg plain bupivacaine and 10 μg fentanyl (1 mL total). A blinded researcher assessed sensory dermatome level, analgesia, and motor blockade at regular intervals for 30 minutes. The primary outcome measure was the median peak sensory dermatome level at 15 minutes.

Results: Fifty-four parturients were analyzed. There was no significant difference in peak sensory dermatome levels at 15 minutes (median difference, 1 dermatome level; 95% confidence interval of median difference, 0 to 2; P = 0.22) and 30 minutes (median difference, 0 dermatome level; 95% confidence interval, -2 to 2; P = 0.76). There was no difference in the time to peak dermatome, minimum pain score, or the time to minimum pain score between groups.

Conclusions: We found no significant difference between groups with regard to sensory dermatome level or pain scores when using EVE compared with NEVE. Our study demonstrates that addition of EVE does not offer superior analgesia when using a CSE technique for parturients requesting labor analgesia.