Effect of transcutaneous electrical nerve stimulation on intraoperative fentanyl and propofol consumption in patients undergoing lumbar discectomy

Introduction: Transcutaneous electrical nerve stimulation (TENS) is a non-invasive electrotherapy technique used to treat acute and chronic pain with a special device that delivers electrical impulses to the skin. Numerous studies have been published for the use of TENS in acute postoperative pain with varying duration of pain relief after TENS, but, it is not clear if TENS is applied preoperatively, how long its effect lasts. This randomised, placebo controlled trial was carried out with the objectives of finding out effect of TENS on intraoperative fentanyl and propofol consumption and postoperative analgesic requirement in patients undergoing lumbar discectomy. Methods: Sixty patients were randomised to two groups i.e. TENS group (Group T) and Sham TENS group (Group S). A conventional TENS current in the form of biphasic square pulse was used at a frequency of 100 Hz and pulse width of 250 micro seconds. The intensity of electrical stimulation was at 20 mili Ampere (mA) for the T group and 0 mA for the S group by the blinded anaesthesiologist. Standard protocols were followed for induction and maintenance of anaesthesia. Heart rate, blood pressure, and BIS were noted regularly after induction. Primary outcome was to compare of the effect of TENS on intraoperative fentanyl requirement and secondary outcomes were its effects on intraoperative propofol consumption and postoperative analgesic requirement. Results: Thirty one patients were studied in group T and 29 patients in group S. Demographic data, duration of surgery, total dose of fentanyl and propofol requirement, blood loss, and the recovery times were comparable between the 2 groups. The mean VAS scores on rest and movementbefore application of TENS preoperatively were 4.71 and 5.9 in group T which significantly reduced after application of TENS to 3.06 and 3.42 respectively. However in the Sham TENS group the mean VAS score did not change significantly. The mean fentanyl consumption in group T was 2.05 ± 0.47 mcg/kg (microgram per kilogram body weight) in group T and 2.20 ± 0.61 mcg/kg in group S (p = 0.27). The mean propofol consumption was 120.39 ± 28.91 mcg/kg/min (microgram per kilogram body weight per minute) in group T, and 117.10 ± 17.91 mcg/kg/min in group S (p = 0.6). Conclusion: Application of TENS significantly reduced the pain in term of decrease in VAS score at rest and movement preoperatively, but the same did not translate into any decrease in intraoperative analgesic or anaesthetic requirement, and neither there was any decrease in postoperative analgesic requirement in patients undergoing lumbar discectomy.