High-dose intraoperative remifentanil infusion increases early postoperative analgesic consumption: a prospective, randomized, double-blind controlled study

Purpose: The purpose of this study was to determine whether intraoperative infusion of remifentanil induces acute tolerance to opioids, and compare the postoperative pain and opioid consumption by the effect site concentrations of remifentanil. Methods: One hundred and ninety-eight patients undergoing gastrectomy were randomly assigned to maintain target effect site concentrations of remifentanil at 0 (Group 1, n = 39), 2 (Group 2, n = 40), 4 (Group 3, n = 39), 8 (Group 4, n = 40), or 12 ng/ml (Group 5, n = 40) during operation. Postoperative pain intensities and fentanyl requirement were recorded at postoperative 2, 6, 24, and 48 h. Results: Fentanyl requirement for postoperative 2 h was significantly greater in Group 5 compared to Group 1 (376 ± 116 vs. 283 ± 129 µg, P = 0.03). However, there were no differences in fentanyl requirements among the groups after postoperative 2 h. Also, total fentanyl consumption for 48 h was similar in all groups (Group 1; 3106 ± 629, Group 2; 2970 ± 705, Group 3; 3017 ± 555, Group 4; 3151 ± 606, and Group 5; 2984 ± 443 µg, P = 0.717). Pain scores at rest and during deep breathing were comparable in all groups at the time of each examination. Conclusion: Intraoperative infusion of remifentanil with 12 ng/ml of effect site concentration in patients undergoing gastrectomy increases early postoperative fentanyl requirement. Acute opioid tolerance would be developed by higher concentration of remifentanil than dosage of common anesthetic practice.