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

Comparison of Different Doses of Remifentanil on Postoperative Pain in Patients Undergoing Thyroidectomy: a Prospective, Double-blinded Randomized Control Trial

Extensive clinical studies have shown that intraoperative infusion high dose of remifentanil (0.2ug/kg/min) induced postoperative hyperalgesia. Recent experimental study however suggests that higher dose of remifentanil may attenuate postoperative hyperalgesia. Thus, the present study is designed as a "proof of principle" study and hypothesizes that higher dose of remifentanil may reduce postoperative pain in patients.

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.

remifentanil(Low):dose of 0.2ug/kg/min. The dose of remifentanil is widely used intraoperatively clinically;

The present study examine two different dose of remifentanil: low dose (0.2ug/kg/min) and high dose (1.2ug/kg/min)

Quantitative sensory threshold in the remote uninjured site (here, the inner forearm) is commonly used to examine the occurrence of postoperative hyperalgesia. The present study will examine the mechanical threshold in two different doses of remifentanil to determine whether high dose of remifentanil induces hyperalgesia

VAS is widely used to assess postoperative pain. It will be divided as 10 points. Zero refers to no pain and ten refers to extremely pain. Based on this way, we can know the difference of postoperative pain in these two different groups.

Inclusion Criteria: ASA Grade I or II Age 18-60 years old BMI<35, Exclusion Criteria: do not consent, Chronic pain, used pain killer, undergoing operation previously diabetes or the other diseases affecting the sensory. difficult intubation; unexpected surgical complication such as bleeding; psychiatric disorders; drug or alchohol abuse

Zhang YL, Ou P, Lu XH, Chen YP, Xu JM, Dai RP. Effect of intraoperative high-dose remifentanil on postoperative pain: a prospective, double blind, randomized clinical trial. PLoS One. 2014 Mar 25;9(3):e91454. doi: 10.1371/journal.pone.0091454. eCollection 2014.