Adjuvant analgesics for spine surgery.

Increasing evidence indicate that pain is insufficiently treated following surgical procedures. It is essential that pain treatment is effective with a minimum of side effects in order to promote postoperative rehabilitation. Multimodal analgesia is most likely an important strategy in reducing postoperative pain. Combinations of different analgesics with different mechanisms of action may have an additive analgesic effect with fewer side effects compared to using a single drug. However, there is still a pronounced lack of documentation for the effect and side effects of these multimodal analgesic regimes. More than 6,000 spine surgeries are performed annually in Denmark and spine surgery has been associated with high levels of pain compared to other surgical procedures. Therefore, we considered spine surgery to pose a group of well-defined surgical procedures and we used this model to investigate the efficacy of 3 adjuvant analgesics aiming to improve the multimodal approach in pain management.
 
In study I and II we hypothesized that preoperative IV dexamethasone 16 mg would reduce acute postoperative pain, opioid consumption and persistent pain after lumbar disk surgery. We found that dexamethasone significantly reduced acute pain during mobilization. The clinical relevance is however debatable and we could not demonstrate an opioid sparing effect. Further, we discovered significantly higher pain levels in the dexamethasone group compared to placebo 1 year postoperatively.
 
In study III we explored the effect of 500 mg of oral chlorzoxazone on acute postoperative pain and opioid consumption in patients with moderate to severe pain after spine surgery and found no effect of chlorzoxazone compared to placebo.
 
In study IV we hypothesized that intraoperative ketamine would reduce postoperative opioid consumption and persistent pain after spinal fusion surgery in chronic pain patients with opioid dependency. We found a significantly reduced opioid consumption in the ketamine group and a reduced level of persistent pain 6 months postoperatively.
 
In conclusion, dexamethasone and ketamine are potential adjuvant analgesics for postoperative pain. Possibly ketamine also inhibits the development of persistent pain. Chlorzoxazone has no immediate effect as an adjuvant in acute pain management.