Recent studies suggest that preemptive analgesia may be effective in reducing postoperative pain. One physiologic explanation may be interference with the endogenous opioid response. We investigated whether long-lasting preoperative preemptive analgesia may have an effect on the hormonal stress response after total hip replacement.
Methods: 42 patients scheduled for elective hip replacement for coxarthrosis were randomized to receive, on the day before the operation, either 5 ml*h(-1) ropivacaine 0.2% (study group, n = 21) or 5 ml*h(-1) saline (control group, n = 21). Postoperative analgesia was achieved in both groups by patient-controlled epidural analgesia (PCEA) with ropivacaine 0.2%. The main outcome measure was the concentration of authentic beta-endorphin [1-31] in plasma up to 4 days after surgery. Additional parameters included concentrations of adrenocorticotrope hormone and cortisol.
Results: Both groups were comparable concerning preoperative parameters and pain scores. Epidural blocks were sufficient in all patients for operative analgesia. Preemptive analgesia was performed for 11-20 hours in both groups and led to significantly decreased pain scores before surgery. Preemptive analgesia with epidural ropivacaine did not lead to decreased concentrations of beta-endorphin [1-31] before the start of surgery or in the postoperative period. Furthermore, no differences could be detected in the time course of beta-endorphin and adrenocorticotrope hormone after surgery. However, cortisol concentrations differed significantly between groups before the operation, but showed a comparable rise after surgery.
Conclusion: Differences in postoperative pain after preemptive analgesia do not seem to be due to an altered endogenous opioid response.