A Comparison of Two Constant-Dose Continuous Infusions of Remifentanil for Severe Postoperative Pain

We evaluated the analgesic efficacy and safety of two continuous constant-dose infusions of IV remifentanil, without infusion rate increments or the addition of boluses, in patients with severe postoperative pain during the first 4 h after general anesthesia with IV propofol-remifentanil. Thirty patients were randomly assigned to two groups of 15 subjects each according to the remifentanil dose administered: 0.1 μg · kg−1 · min−1 IV (Group A) or 0.05 μg · kg−1 · min−1 IV (Group B). Rescue analgesia was provided with meperidine (0.5 mg/kg IV) when pain intensity on the simple verbal scale (SVS) ≥2. The criteria for adequate analgesia (SVS 0–1, respiratory frequency >8/min. and Spo2 >90%) after 4 h were met by 78% and 75% of the patients in Groups A and B, respectively (P = ns). “Meperidine rescue” analgesia was significantly more in Group B (26%) than in Group A (6%) (P < 0.05). There were no cases of respiratory depression, and nausea and emesis occurred in one patient in each group (6.5%). We conclude that IV remifentanil is an effective and safe opioid for the treatment of postoperative pain at a constant dose of 0.1 μg · kg−1 · min−1 with a need for rescue analgesia 4 times less than a constant dose of 0.05 μg · kg−1 · min−1.