Transcutaneous Electrical Acupoint Stimulation Can Alleviate Remifentanil-induced Hyperalgesia

【Object】Remifentanil is commonly used in general anesthesia due to its unique pharmacokinetic characteristics — a predictable and rapid recovery that is independent of the dose and duration of infusion. However, considerable evidence have demonstrated that exposure to high-dose remifentanil leading to opioid-induced hyperalgesia(OIH). OIH is characterized by an increase in pain intensity, distribution or sensitivity elicited by high-dose or prolonged opioids, which will result in greater postoperative analgesic consumption, higher pain scores and poorer patient satisfaction. Transcutaneous electric acupoint stimulation(TEAS), a non-invasive technique, can be applied by personnel with minimal training. Several clinical trials have demonstrated that TEAS has the potential to reduce postoperative pain and perioperative analgesic consumption. However, the effects of TEAS on remifentanil induced hyperalgesia remains unknown. In this prospective, randomized, double-blind study, we investigated whether TEAS can alleviate remifentanil-induced hyperalgesia in patients undergoing thyroidectomy.【Methods】60 American Society of Anesthesiologists physical status(ASA)Ⅰ-Ⅱpatients, aged 18–60 year, scheduled for thyroidectomy were randomly allocated to TEAS or control groups. TEAS consisted of 30 min of stimulation(6–9m A, 2/10Hz) on the Hegu(LI4) and Neiguan(PC6) before anesthesia. The patients in the control group had the electrodes applied, but received no stimulation. Standard monitoring, including electrocardiogram(ECG), noninvasive blood pressure(NIBP), peripheral oxygen saturation(Sp O2), and tympanic membrane temperature, bispectral index(BIS) monitor was applied to all patients. Anesthetic induction was achieved with propofol 2 mg/kg and remifentanil(effect site target concentration of 5.0 ng/ml). Upon patient loss of consciousness, cisatracurium 0.15 mg/kg was administered to facilitate tracheal intubation. Anesthesia was maintained with sevoflurane adjusted to BIS(40–60) and target remifentanil 5.0 ng/ml. Mechanical pain thresholds on the nondominant forearm and peri-incisional areas were assessed using electronic von Frey. The primary outcome was mechanical pain thresholds. Secondary outcomes included postoperative pain scores, the time to first rescue analgesic, cumulative number of rescue analgesia, and side effects, including postoperative nausea and vomiting(PONV), shivering and dizziness in 24 h postoperatively.【Results】Baseline mechanical pain thresholds were similar between the groups. The analysis revealed the decrease in mechanical threshold was greater in the control group than the TEAS group(P < 0.001). Postoperative pain scores and cumulative number of rescue analgesia were lower in the TEAS group(P < 0.05). In addition, TEAS group patients reduced the incidence of PONV and shivering.【Conclusion】Preoperative TEAS can alleviate remifentanil-induced hyperalgesia in patients undergoing thyroidectomy.