INTRAARTICULAR MORPHINE ANALGESIA AFTER A RTHROSCOPIC KNEE SURGERY - A DOUBLE-BLIND, RANDOMIZED STUDY OF PATIENT-CONTROLLED ANALGESIA

Previous studies investigating the peripheral action of locally instil led morphine after arthroscopic knee surgery found evidence for an ana lgesic effect. Follow-up studies have lead to conflicting results. We used patient-controlled analgesia (PCA) to test the analgesic potency of intraarticular morphine. Methods. arthroscopic general anaesthesia received, after written informed consent and in double-blind and rando mised manner, I mg morphine diluted in 10 mi saline either intraarticu larly or intravenously at the end of the surgical procedure. A control injection of 10 mi saline was given at the other site. The pain inten sity on a visual analogue scale (VAS) and the cumulative morphine cons umption were recorded at 1, 2, 3, 4, 6, 8 and 24 h after the end of ge neral anaesthesia. Statistics: Wilcoxon rank sum test with P<0.05. Res ults. A total of 59 patients were included in the study; 29 received m orphine intraarticularly (verum group), 30 intravenously (control grou p). There was no difference in gender, age, duration of arthroscopy or anaesthesia. There were more than 60% diagnostic arthroscopies in bot h groups; other types of surgery were comparable, with the exception o f cruciate band repair procedures only in the control group. We found no difference in morphine consumption or pain intensity between the tw o groups throughout the study period, Median overall consumption of mo rphine after 24 h was 14 mg in the verum in the control 15 mg wide int erindividual variation. Pain intensities were remarkably low. The peak pain intensity of both groups was found at 1 h postoperatively, with median 16/100 on the VAS in both groups. Blinding was robust. Conclusi on. We found no reduction in postoperative morphine supplementation af ter 1 mg morphine intraarticularly compared to 1 mg intravenously give n at the end of knee arthroscopies. There were also no differences in pain intensities on a VAS. We conclude that titration of postoperative pain with a morphine-filled PCA pump was unable to show a difference in analgesic potency between intraarticular and intravenous morphine.