The Effect of Location of Transcutaneous Electrical Nerve Stimulation on Postoperative Opioid Analgesic Requirement

Abstract

Transcutaneous electrical nerve stimulation (TENS) has been used as a complementary (supplemental) therapy to opioid analgesics for pain relief after surgery.Simultaneous stimulation at a classical Chinese acupoint site and periincisional dermatomes significantly decreases the postoperative analgesic requirement. This sham-controlled study was designed to assess the relative effectiveness of acupoint versus nonacupoint stimulation on the postoperative hydromorphone (HM) requirement, the incidence of opioid-related side effects, and the overall recovery profile. One hundred women undergoing total abdominal hysterectomy or myomectomy procedures with a standardized general anesthesia were randomly assigned to one of four postoperative analgesic treatment regimens (n = 25 each): Group I = sham-TENS (no electrical current) at the Zusanli (ST36) acupoints, Group II = nonacupoint-TENS at the shoulders, Group III = dermatomal-TENS at the level of the surgical incision, and Group IV = acupoint-TENS at the Zusanli acupoints. The frequency of TENS was set in the standard dense-and-disperse mode of 2/100 Hz. The intensity of stimulation was set at 0 mA for patients in Group I and at 9-12 mA for patients in Groups II, III, and IV. A patient-controlled analgesia (PCA) device programmed to deliver bolus doses of HM 0.2-0.4 mg IV on demand with a minimal lockout interval of 10 min was used to quantify the postoperative opioid analgesic requirement. Standard 100-mm visual analog scales were used to assess pain, as well as sedation, fatigue, and nausea, at specific intervals after surgery. The numbers of PCA demands and delivered bolus doses, requirements for supplemental medication, and any opioid-related side effects were recorded. In the first 24 h postoperatively, the opioid requirements in Groups III and IV were decreased by 37% and 39%, respectively, compared with the control (sham) group and 35% and 38%, respectively, compared with Group II. The duration of PCA usage and the incidences of nausea and dizziness were also significantly decreased in Groups III and IV compared with Groups I and II. We conclude that periincisional dermatomal and Zusanli acupoint stimulation were equally effective in decreasing the postoperative opioid analgesic requirement and in reducing opioid-related side effects. Both of these positions were more effective than the nonacupoint (shoulder) location. Implications: The location of the stimulating electrodes seems to be an important determinant of the efficacy of transcutaneous electrical nerve stimulation in decreasing the need for opioid analgesics in the postoperative period. This study demonstrates that transcutaneous electrical nerve stimulation applied at the dermatomal level of the skin incision is as effective as Zusanli acupoint stimulation, and both were more effective than stimulation at a nonacupoint (shoulder) location. (Anesth Analg 1998;87:1129-34)