Does Changes in the Electrical Resistance of an Acupuncture Meridian Predict Pain Intensity Following Orthopedic Surgery?

BACKGROUND Several methods for assessment of severity of pain have been proposed but all of them are subjective. OBJECTIVES This study evaluated the association concerning changes in electrical resistance (ER) between two acupuncture points and severity of postoperative pain in order to define an objective measurement of pain. PATIENTS AND METHODS In a cross-sectional study, 50 patients undergoing lower extremity orthopedic surgery with postoperative moderate to severe pain (VAS > 4,) were consecutively enrolled. In the recovery room, the patients' pain scores were assessed and in patients with VAS > 4, the electrical resistance between Li4 and Li11 acupuncture points as well as pain scores was measured prior and following analgesic administration. RESULTS Following meperidine use, the mean VAS significantly decreased and the ER between the two acupoints was significantly increased. However, Pearson correlation analysis did not reveal any association between the trends of pain intensity and ER (P > 0.05). The ER change in patients operated under epidural anesthesia was significantly less than those who experienced general or spinal anesthesia. CONCLUSIONS There is a coincidence of pain relief and change in the ER of acupuncture meridians without significant association. The diagnostic value of ER for pain, stress response or any other physiologic outcome needs to be investigated in clinical trials with a well-defined control group, with more accurate instruments and probably in different acupuncture meridians.