Efficacy and safety of equi-analgesic opioid conversion-based postoperative pain management for patients with chronic opioid use

Background: Few prospective study examined the optimal postoperative opioid dose setting for chronically opioid consuming patients. We prospectively investigated whether postoperative pain control based on the equianalgesic conversion of the preoperative opioid dose is a safe and adequate way of relieving postoperative pain in patients with chronic opioid use. Methods: The patients were allocated into the high dose group (HG) or the low dose group (LG) according to their preoperative doses of opioid. After surgery, the patients received intravenous morphine using a patient-controlled analgesia (PCA) pump which was set based on their preoperative opioid dose. The numerical rating scale (NRS) pain score, 24 hr cumulative morphine consumption, and the incidence of adverse events were compared between the groups. Results: A total of seventeen patients (HG I n=9, LG; n=8) were enrolled. The worst NRS pain score was significantly higher in HG than in LG. No serious adverse events due to overdose occurred in either group. Conclusions: Our PCA regimen appears to be safe overall; however it is still inadequate for relieving postoperative pain in patients taking high preoperative opioid doses.