Transcutaneous electrical nerve stimulation does not augment combined spinal epidural labour analgesia

Abstract

Purpose: The spinal portion of the combined spinal epidural technique (CSE) provides dramatic but limited labour analgesia. Transcutaneous Electrical Nerve Stimulation (TENS) has been noted to modulate pain, in part by the frequency of stimulation chosen. Because nerve action potentials are blocked by local anesthestics in a frequency dependent manner, we speculated that a TENS unit could increase the quality and duration of the spinal portion of a CSE. Methods: Forty parturients in active spontaneous labour, with a singleton, vertex, term fetus, requesting analgesia were enrolled in a randomized, double blind fashion to receive a standardized CSE with either an active or inactive TENS unit. Prior to CSE placement, TENS intensity thresholds were determined with electrodes placed on the paraspinus muscles at T10-L1, and S2-4; TENS settings for mode, cycle, and pulse width were standardized. Data were collected at timed intervals on pain (VAS), sensory level (pinprick), motor blockade (Bromage), cervical dilatation, and duration of analgesia, and at delivery on fetal and neonatal outcome. Results: The duration of the spinal portion of the CSE did not differ between groups (TENS off 91.1 ± 33 [mean ± SD] vs TENS on 83.1 ± 28 min, P=.42). Kaplan-Meier survival analysis and Mantel-Cox log rank analysis showed no difference between the two treatments (P=.28). Analgesia was comparable throughout the first hour of spinal analgesia. Conclusion: In healthy labouring parturients, the application of a TENS unit did not alter the quality or duration of labour analgesia provided by the spinal portion of CSE analgesia.