Kim D, et al. - In a total of 198 patients undergoing gastrectomy, researchers investigated if intraoperative infusion of remifentanil induces acute tolerance to opioids. They compared the postoperative pain and opioid consumption by the effect site concentrations of remifentanil. Intraoperatively, patients 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). Assessments for postoperative pain intensities and fentanyl requirement were carried out at postoperative 2, 6, 24, and 48 h. They noted an increased early postoperative fentanyl requirement related to intraoperative infusion of remifentanil with 12 ng/ml of effect site concentration. Compared with dosage of common anesthetic practice, acute opioid tolerance would be developed by higher concentration of remifentanil.