Remifentanil infusion in association with fentanyl-propofol anaesthesia in patients undergoing cardiac surgery: Effects on morphine requirement and postoperative analgesia

Background: We have prospectively assessed the effects of remifentanil on morphine requirement in the first hour after emerging from general anaesthesia after elective coronary artery bypass surgery and in the first 12 h postoperatively, and pain and agitation scores in the first hour after emerging from general anaesthesia. Methods: Twenty patients undergoing off-pump coronary artery bypass surgery, receiving standardized propofol-fentanyl-based anaesthesia, randomly received infusions of either remifentanil 0.1 μg kg ^-1 min ^-1 (Group R, n=10) or saline (Group S, n=10), each infused at 0.12 ml kg ^-1 h ^-1. Propofol and trial drug infusion were continued into the postoperative period until the patients were ready to be woken up. Postoperative analgesia was provided with morphine infusion commenced immediately after operation, and was additionally nurse controlled on the basis of a visual analogue scale (VAS) score (0-10). Agitation score was recorded using a VAS of 0-3. Results: In the first hour after discontinuing propofol and trial infusion, morphine requirements were significantly higher in the remifentanil group (8.15 (SD 3.59) mg) compared with the saline group (3.29 (2.36) mg) (p<0.01). There was no difference in the total morphine given during the period after stopping propofol or in the total requirement in the first 12 h postoperatively. There was no significant difference in either pain scores or agitation scores between the two groups. Conclusion: Use of remifentanil is associated with increased opioid requirement in the first hour after it has been discontinued.