Intraarticular fentanyl compared with morphine for pain relief following arthroscopic knee surgery

To compare the analgesia produced by comparable doses of intra-articular (IA) morphine and fentanyl.

Sixty-nine healthy patients undergoing arthroscopic surgery received a standardized general anesthetic of 4 mg x kg(-1) thiopental and 2 microg x kg(-1) fentanyl followed by 2 mg x kg(-1) succinylcholine prior to tracheal intubation and controlled ventilation. Maintenance of anesthesia was achieved with N2O/O2 and isoflurane. At the conclusion of surgery intra-articular injection was: Group I (n=23) 50 microg fentanyl in 20 ml saline; Group II (n=24) 3 mg morphine in 20 ml saline; Group III (n=22) 20 ml saline. Pain scores at rest using a visual analogue scale were recorded by a separate blinded observer at one, two, four, and eight hours postoperatively.

Pain scores at one, two, four, and eight hours were 36, 26.3, 20.9, and 12.8 vs 35.8, 33.8, 28.8, and 21.9 vs 70.5, 57.7, 58.4, and 53.6 for the IA-fentanyl, IA-morphine, and control groups respectively. Pain scores were greater at all times for Group III. Pain scores for Groups I and II were similar at one hour, but thereafter were less (P < 0.001) for the IA-fentanyl group.

Better postoperative analgesia was achieved with 50 microg intraarticular fentanyl than with 3 mg intraarticular morphine.