Anesth Analg 1999;89:1236
© 1999 International Anesthesia Research Society
REGIONAL ANESTHESIA AND PAIN MANAGEMENT
Transcutaneous Electrical Nerve Stimulation as an Alternative Therapy for Microlaryngeal Endoscopic Surgery
Shigeyoshi Toyota, MD*,
Tsukasa Satake, MD*, and
Yoshikiyo Amaki, MD
Departments of Anesthesiology,
*Jikei University, Kashiwa Hospital, Kashiwa, Chiba and
Jikei University School of Medicine, Minato-ku, Tokyo, Japan
Address correspondence and reprint requests to S. Toyota, MD, Department of Anesthesiology, Tsudanuma Chuoh General Hospital, 1-9-17 Yatsu, Narashino, Chiba 275-0026, Japan.
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Introduction
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Microlaryngeal endoscopic surgery provides considerable hemodynamic stress, and its surgery operative time is usually short. We have used narcotics sparingly because of their undesirable side effects, such as respiratory depression, sedation, nausea, and vomiting. Transcutaneous electrical nerve stimulation (TENS) is commonly used to control pain. It was introduced into clinical practice in 1972 as an adjunct to other pain therapies. The mechanism of action of TENS is still not completely understood. Analgesia may be produced by the modulation of nociceptive input in the dorsal horn of the spinal cord by peripheral electrical stimulation of large sensory afferent nerves. This is the "gate control theory" of pain. Alternatively, electrical stimulation of certain receptor sites in the dorsal horn of the spinal cord may release endorphins, in turn, producing analgesia that can be reversed by naloxone (1,2). The aim of this study was to evaluate the effect of TENS as analgesia for microlaryngeal endoscopic surgery.
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Methods
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After obtaining approval from the Protection of Human Subjects Committee of Jikei University Hospital and informed consent from each patient, we studied 45 adult patients (ASA physical status I or II), undergoing microlaryngeal endoscopic surgery. We excluded patients who had cardiovascular diseases and those who were receiving drugs (antihypertensive, antidepressants, etc.) that influence minimum alveolar anesthetic concentration. Each patient was randomly assigned to one of three groups: general anesthesia (Control group, n = 15), general anesthesia with fentanyl (Fentanyl group, n = 15), or general anesthesia with TENS (TENS group, n = 15). Anesthesia was induced with thiamylal (4 mg/kg) IV and vecuronium (0.1 mg/kg) IV, after which the trachea was intubated, and ventilation was controlled to maintain the end-tidal CO2 in the range of 30–40 mm Hg. Lactated Ringer’s solution was infused at 3–5 mL · kg-1 · h-1.
The Control group received isoflurane (1%–1.5%), nitrous oxide (66%), and oxygen (33%). The Fentanyl group received the same as the Control group but with the addition of fentanyl (2 µg/kg) IV during the induction of anesthesia. The TENS group recieved the same as the Control group but with the addition of TENS, via Silver Spike Point (SSP) electrodes (Nihon Medix, Chiba, Japan) for continuous stimulation (5 Hz) with Trimix 1 (Nihon Medix). Pore sites were bilateral Gokoku (Hoku LI4, on the back of the hand between the bases of the first and second metacarpals) and Ashisanli (Tsusanli ST36, 3-cm lateral to the inferior ridge of the tibial tuberosity) acupoints. Before the induction of anesthesia, the voltage was set to a level that was immediately before each patient felt subjective pain. Electrical stimulation was performed until the end of surgery.
We measured systolic (SAP), diastolic (DAP), and mean (MAP) arterial pressures and heart rate (HR) with an automated, noninvasive measurement device (BP-203i, Nippon Colin, Tokyo, Japan), before and 90 s after the insertion of the laryngeal scope. We administered nicardipine, 1 mg IV, when SAP was more than 25% of the baseline value and counted the number of administrations of nicardipine in each group during anesthesia. Results were analyzed using analysis of variance followed by a Bonferroni t-test and Kruskal-Wallis test. P < 0.05 was considered significant.
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Results
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There were no significant differences among the groups in age, height, body weight, anesthetic time, and the time to tracheal extubation (Table 1). HR and SAP were significantly lower in anesthetized patients receiving fentanyl compared with the Control and TENS groups before laryngoscopy. DAP and MAP were also lower in anesthetized patients receiving fentanyl compared with the Control group before laryngoscopy. DAP was significantly lower in anesthetized patients receiving TENS compared with the Control group before laryngoscopy. In the TENS group, the increase of HR, DAP, and MAP was significantly inhibited compared with the Control group postlaryngoscopy. In the Fentanyl group, the increase of all hemodynamic variables was inhibited significantly compared with the Control group postlaryngoscopy (Table 2). The TENS and Fentanyl groups showed a decreased use of nicardipine compared with the Control group: TENS group, 0 (0–1); Fentanyl group, 0 (0–1); Control group, 1 (0–4) [values are median (range)].
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Discussion
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The increased HR, DAP, and MAP associated with microlaryngeal endoscopic surgery was attenuated by TENS. The potential advantages of TENS are that it is noninvasive and safe. Its mechanism of action, however, is still not completely understood. Analgesia may be produced by the modulation of nociceptive input in the dorsal horn of the spinal cord by peripheral electrical stimulation of large sensory afferent nerves, the gate control theory of pain. Alternatively, electrical stimulation of certain receptor sites in the dorsal horn of the spinal cord may release endorphins, in turn, producing analgesia that can be reversed by naloxone (1). The Fentanyl group showed a significantly decreased HR, SAP, DAP, and MAP before laryngoscopy compared with the Control group. These effects were caused by opioid-induced bradycardia, and they are side effects of fentanyl; however, fentanyl inhibited an increase of all hemodynamic variables compared with the Control group.
We used the SSP electrodes. Hyodo and Kitade (3) developed SSP therapy, a surface acupuncture-point stimulation therapy in which low frequency electricity is passed to a surface point through SSP electrodes. (This therapy is also called "transcutaneous electrical acupuncture point stimulation therapy.") The SSP electrode is a silver-plated, spike-like, triangular-cone electrode that is placed on an acupoint and fixed by a band or tape. The effect is similar to the stimulation effect of an inserted needle, in which SSP therapy is called "needleless acupuncture" (4).
Acupuncture can activate the body’s pain modulation system and increase the release of endogenous opioids within the central nervous system (5). We used the Gokoku point on the hand because it is alleged to be one of the most effective pain-relieving acupoints.
The limitations of our study were that the sample size was small and our study was neither double-blinded nor designed to use sham stimulation in a controlled group. The patients were anesthetized, and the anesthesiologists were aware of the group in which each patient was allocated and could, therefore, have introduced bias. We are convinced that the bias was minimal, however, because the anesthesiologists were not aware of the study design.
In conclusion, the effects of TENS were nearly equal to fentanyl in microlaryngeal endoscopic surgery. TENS may be considered an alternative pain management for microlaryngeal endoscopic surgery.
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References
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Brodsky JB, Mark JBD. Postthoracoscopy pain: TENS the answer? Ann Thorac Surg 1997;63:608–10.[Free Full Text]
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Benedetti F, Amanzio M, Casadio C, et al. Control of postoperative pain by transcutaneous electrical nerve stimulation after thoracic operations. Ann Thorac Surg 1997;63:768–72.[Abstract/Free Full Text]
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Hyodo M, Kitade T. A guide to silver spike point (SSP) therapy. 2nd ed. Tokyo:The Silver Spike Point Therapy Study Group, 1979.
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Sugimoto K, Konda T, Shimahara M. A clinical study on SSP (Silver Spike Point) electro-therapy combined with splint therapy for temporo-mandibular joint dysfunction. Electrother Res 1995;20:7–13.
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Wang B, Tang J, White PF, et al. Effect of the intensity of transcutaneous acupoint electrical stimulation on the postoperative analgesic requirement. Anesth Analg 1997;85:406–13.[Abstract]
Accepted for publication June 22, 1999.
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Introduction
Methods
