[Intra-operative ketamine administration reduced the level of post-thoracotomy pain]

Two different types of post-operative pain (such as acute pain and chronic pain) occur in patients undergoing thoracotomy. It has been suggested that the acute post-thoracotomy pain consists of inflammatory pain and chronic post-thoracotomy pain caused by intercostal neuralgia. In the present study, we examined the effect of intra-operative administration of ketamine, an NMDA receptor antagonist, on the acute and chronic post-thoracotomy pain.

Sixteen patients were assigned to one of two groups (ketamine or control). The ketamine group received a ketamine bolus (1 mg x kg(-1)) just before the skin incision, followed by continuous infusion of ketamine (1 mg x kg(-1) x hr(-1)) during surgery.

Verbal rating scores (VRSs) at rest and on cough were significantly lower in the ketamine group on day 1 and VRS of chronic pain was also significantly lower in the ketamine group 4 weeks after the surgery.

These data suggest that post-thoracotomy pain might be mediated by NMDA receptor dependent central sensitization and that the intra-operative administration of ketamine might block the development of the NMDA receptor dependent central sensitization.