Effect of Higher Doses of Remifentanil on Postoperative Pain in Patients Undergoing Thyroidectomy

Remifentanil, an ultra-short acting opioid, is widely used in the patients undergoing surgery. However, extensive studies report that remifentanil,administered at 0.2ug/kg/min or 0.4ug/kg/min intraoperatively, can result in postoperative hyperalgesia and increase the consumption of analgesics when compared with low dose (0.05ug/kg/min). However, a recent experimental study shows that large dose of remifentanil can inhibit pain hypersensitivity through erasing the spinal sensitization of pain. The present study thus hypothesizes that higher dose of remifentanil (1.2ug/kg/min) may attenuate postoperative pain. The present study will compare the effect of two different dose of remifentanil (0.2ug/kg/min and 1.2ug/kg/min) on postoperative pain. Patients undergoing thyroidectomy will be recruited, and mechanical threshold will be measured in the remote region of surgical site preoperatively. The patients will be randomly divided by two groups, 0.2ug/kg/min (group I) and 1.2ug/kg/min (group II). After operation, mechanical threshold and visual analogue scale (VAS) will be measured as the indicators of postoperative pain. The consumption of morphine will also be compared between these two doses of remifentanil.

The present study may find optimized dose of opioid usage in the patients undergoing surgery to relieve the postoperative pain.