Hydromorphone versus morphine: a historical cohort study to evaluate the quality of postoperative analgesia

Opioids are the most widely used therapy for pain during the postoperative period. It has been suggested by some that hydromorphone is clinically superior. Our primary objective was to determine if there is a difference in postoperative pain score ratings between adult patients receiving intravenous hydromorphone vs intravenous morphine on discharge from the post-anesthesia care unit (PACU).

For this historical cohort study, convenience sampling was used to identify the first 605 patients ≥ 18 yr undergoing elective, non-cardiac surgery. Patients were categorized based on treatment in the PACU with hydromorphone (n = 326) or morphine (n = 279). Pain scores (scale of 0-10), nausea/vomiting (scale of 0-3), pruritis (scale of 0-3), and sedation (scale of 0-4), as well as total opioid dose administered from arrival in the PACU until readiness to discharge were evaluated.

For the primary outcome of pain reported at discharge from the PACU, there was no significant difference between the mean (standard deviation) hydromorphone numeric rating scale (NRS) [2.8 (1.6)] and the morphine NRS [2.5 (1.5)] after adjusting for potential confounders (adjusted mean difference, 0.10; 95% confidence interval, -0.21 to 0.42; P = 0.53). Similarly, there were no significant between-group differences in length of stay in the PACU, satisfactory analgesia, nausea/vomiting, and sedation.

This study serves to help guide the decision-making process for selecting either morphine or hydromorphone for acute postoperative analgesia. Overall, we found no significant difference for analgesia or for common opioid-related adverse effects between these two opioids in the postoperative period at the time of discharge from the PACU. Furthermore, according to this data, the equipotency ratio of hydromorphone to morphine is closer to 1:6.5 rather than the commonly employed 1:5 ratio.