Evaluation of the effects of different infusion doses of remifentanil on postoperative shivering

Introduction: Postoperative shivering is a common anesthetic complication occurring mainly after general anesthesia just like pain and PONV. Postoperative shivering usually occurs as a type of thermoregulatory response toward hypothermia, but postoperative shivering may occur even when the body temperature is within normal temperature limits due to pain, uninhibited spinal reflexes, decreased sympathetic activity, respiratory alkalosis, age, sex, drug choice and duration of surgery. Exact mechanism for postoperative shivering is not understood yet. Remifentanil is a µ receptor agonist which is an ultra-short acting opioid that contributes to rapid recovery after anesthesia. Remifentanil is used mainly as an analgesic adjuvant to inhalation anesthetics. In literature postoperative shivering of remifentanil has been reported to increase according to increase in infusion dose. Our aim in this study is to compare the effects of different doses of remifentanil infusion on postoperative shivering. Material/Methods: After obtaining ethics committee approval and written informed consent from the patients, 80 ASA 1-2 patients scheduled for mastectomy and thyroidectomy between October-December 2019 were enrolled in the study. Hemodynamic variables, intraoperative temperature values and anesthetic management of the patients during the surgery and PACU stay were recorded. BSAS, VAS, MAS scores of the patients were also recorded. 37 patients were found to receive low dose (0.05-0.1 mcg/kg/min) remifentanil infusion and 43 patients were found to receive high dose (0.15-0.2 mcg/kg/min) remifentanil infusion. Results: Demographic variables, medical history of the patients and intraoperative body temperatures and their changes, visual analog scores at different time points were similar. Extubation time and MAS at PACU were different between groups. BSAS scores at 0 and 10.minutes were also statistically different. There was no statistically significant difference between patients with different genders, ages and BMIs. Conclusion: Thyroid and breast surgery patients anesthetized by inhalational anesthetics in combination with remifentanil infusion postoperative shivering was found to be higher in high dose group when compared to low dose. It should be kept in mind that a frequently used adjuvant remifentanil can result in shivering especially in high doses and this shivering should be treated with non/pharmacologic methods. Keywords: postoperative shivering, remifentanil, BSAS