Opioid requirement after arthroscopy is associated with decreasing glucose levels and increasing PGE2 levels in the synovial membrane.

BACKGROUND

Increased prostaglandin E2 (PGE2) release has been suggested to contribute to the enhanced nociceptor sensitivity that underlies chronic osteoarthritis pain. We have previously shown increased levels of lactate and glycerol in synovium postoperatively. Thus, we wanted to investigate whether the local trauma response is related to subjective pain.

METHODS

We monitored metabolic and inflammatory changes with microdialysis in the knee joint synovial membrane of 14 patients after arthroscopy, in relation to pain requiring systemic opioids. The adipose tissue of the contralateral thigh served as reference. The concentrations of glucose, lactate, pyruvate, glycerol and PGE2, and also local blood flow were analyzed over 3 hours postoperatively.

RESULTS

In the 6 patients requiring systemic opioid analgesia, the initial concentrations of glucose and PGE2 in the synovial tissue were increased compared to those not requiring opioids, and decreased following opioid administration. In the reference tissue there was no difference between groups regarding glucose, and the PGE2 concentration was below the detection limit. No significant differences in the levels of other compounds, in relation to the need for opioids, were found, either in synovial tissue or in reference tissue. Overall, the synovial tissue blood flow was stable.

INTERPRETATION: Pain after arthroscopy is reflected by increased glucose utilization and PGE2 production by the synovial membrane.