| Summary: | Remifentanil, an ultra-short-acting opioid, is widely used for pain control during surgery. However, regular dose (RD) remifentanil exacerbates postoperative pain in a dose-dependent manner. Recent studies suggest that high-dose (HD) remifentanil offers sustained analgesia in experimental studies. We thus hypothesized that intraoperative administration of high-dose remifentanil may attenuate postoperative pain.In this prospective, randomized, double blind, controlled clinical study, sixty patients undergoing thyroidectomy (18-60 years-of-age) received an intraoperative infusion of 0.2 (RD group) or 1.2 μg kg(-1) min(-1) (HD group) remifentanil during thyroidectomy. A visual analogue scale (VAS) was used to measure pain intensity. Mechanical pain threshold on the forearm was assessed using von Frey filaments before surgery (baseline), 2 h postoperatively and 18-24 h postoperatively. The primary outcome was to compare the difference of VAS score at different time points after operation and morphine consumption 24 h postoperatively between RD and HD groups. The second outcome was to compare the difference of mechanical pain thresholds in the forearm postoperatively between RD and the HD groups.VAS scores were lower 30 min postoperatively in the HD group (1.29 ± 1.67, 95% CI 0.64-1.94) compared with the RD group (2.21 ± 1.67, 95% CI 1.57-2.84) (t = 3.427, p = 0.0043, RD group vs. HD group). Postoperative morphine consumption was much lower in the HD group compared with the RD group (1.27 ± 1.88 mg vs. 0.35 ± 1.25 mg, p = 0.033). In both groups, mechanical pain threshold was decreased 18-24 h postoperatively (2.93 ± 0.209 Ln(g) vs. 3.454 ± 2.072 Ln(g), p = 0.032 in RD group; 2.910 ± 0.196 Ln(g) vs. 3.621 ± 0.198 Ln(g), p = 0.006 in HD group, 18-24 h postoperatively vs baseline).Intraoperative administration of high-dose remifentanil decreased VAS scores and morphine consumption postoperatively. Thus, modulation of intraoperative opiates may be a simple and effective method of postoperative pain management.This trial is registered in ClinicalTrials.gov, with the Name: Effect of Higher Doses of Remifentanil on Postoperative Pain in Patients Undergoing Thyroidectomy, and ID number: NCT01761149.
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