There is a well established association between acute inflammation and pain sensation but the exact correlation between the two is poorly understood. The role of prostaglandin E2 (PGE2) as an inflammatory mediator is also well established and this trial sought to determine any direct link between the specific concentration of PGE2 at the sight of local inflammation and the pain experienced by a patient.

21 patients undergoing knee arthroscopy were investigated as part of the study and in each case an inter-articular catheter was placed into the knee joint at the end of the operation. The catheter allowed clinicians to drain synovial fluid from the inflamed post-operative knee, in which they could measure levels of PGE2 and compare those results to the pain described by each patient on a five point, verbal rating scale (none, mild, moderate, severe or intolerable).

Where patients experienced only mild pain or none at all, synovial fluid was drained one hour after surgery. Where patients described moderate pain or worse, fluid was drained immediately and intra-articular analgesia administered to control the pain.

The trial results indicated a statistically significant correlation between raised PGE2 and increased pain sensation. The 10 patients who reported at least moderate pain had a median PGE2 concentration of 2949pg/ml (range: 1091-8322pg/ml) as compared to the 11 patients with just mild pain or none at all, whose median PGE2 concentration was just 950pg/ml (range: 118-1560pg/ml). The association would suggest that novel agents designed to specifically reduce PGE2 levels may be useful in controlling pain associated with post-operative acute inflammation.

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