Evaluation of the transcutaneous electrical nerve stimulator for postoperative analgesia following cardiac surgery

The effectiveness of transcutaneous electrical nerve stimulation (TENS) in postoperative pain relief was assessed in this prospective randomised controlled study of 31 patients during the first 72 hours after cardiac surgery. Fourteen patients were given functioning TENS units, and seventeen patients were given non-functioning units. Postoperative pulmonary function tests, analgesic requirements and the incidence of atelectasis were compared in the two groups. Morphine requirement was significantly reduced on the second postoperative day and peak expiratory flow rates (PEFR) were significantly improved for the first two postoperative days in patients with functioning TENS units. The forced vital capacity (FVC) was significantly larger with functioning TENS units on the second postoperative day, but there were no other significant differences in forced expiratory volume in one second (FEV1) or forced vital capacity (FVC) values between the two groups. A questionnaire given to patients assessing their opinions of the effectiveness of the TENS unit for analgesia showed a placebo effect in some patients with non-functioning units. In summary, this study suggests that TENS may be of benefit in postoperative pain relief after cardiac surgery, especially on the second postoperative day.