• Anders Stålman, Jon A Tsai, Märta Segerdahl, Elisabeth Dungner, Peter Arner, and Li Felländer-Tsai.
• Divisions of Orthopedic, Department of Clinical Science Intervention and Technology, Karolinska Institutet at Karolinska University Hospital, Huddinge, Sweden. anders.stalman@ki.se
• Reg Anesth Pain Med. 2009 Nov 1; 34 (6): 557-64.

ObjectiveOur aim was to study local synovial metabolism, inflammation, and subjective pain scoring after intra-articular injection of morphine, ketorolac, or placebo in knee arthroscopy.MethodsSixty patients undergoing knee arthroscopy were randomized into 3 groups receiving morphine, ketorolac, or placebo before surgery. Microdialysis of the synovial membrane was performed in 10 patients in each group 4 hrs postoperatively. Lactate, glucose, glycerol, glutamate, and prostaglandin E2 (PGE2) were monitored regarding biochemical compounds and visual analog scale regarding perceived postoperative pain.ResultsKetorolac effectively attenuated postoperative PGE2 levels. Glycerol increased over time in the ketorolac group. Glutamate showed a decrease over time in both the morphine and ketorolac groups. Differences in PGE2 in the reference tissue indicated a systemic effect of ketorolac. There were no effects on subjective pain scoring (visual analog scale).ConclusionsTo our knowledge, this is the first study on the local metabolic and inflammatory effect of intra-articularly administered morphine or ketorolac. For the first time, glutamate was studied in synovial tissue, and our results suggest that local release of glutamate may be important for nociception and inflammation. The effects of ketorolac on PGE2 implicates a local effect on inflammation and possibly, also nociception, but it should be remembered that 60 mg of ketorolac given intra-articularly also has a systemic effect. Release of glycerol after administration of ketorolac may indicate a toxicity of nonsteroidal anti-inflammatory drugs that must be further evaluated.

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