Methods: ED patients who were prescribed intravenous hydromorphone or morphine as their initial analgesic were enrolled at the time of opioid administration, then re-interviewed 1-2 hours later. Informed consent was obtained by trained ED enrollers, following an IRB-approved protocol. Patients who were taking opioids at home upon presentation and those who received supplemental analgesics between the pre- and post-opioid surveys were excluded from the statistical analysis to allow direct comparison of the opioid dose effects.

Results: A total of 638 patients were enrolled; 323 patients remained after the above exclusions, with 20% receiving hydromorphone. Hydromorphone was administered at much higher doses than morphine (8.5mg or 0.095mg/kg vs. 3.7mg or 0.046mg/kg, p<0.0001, assuming 10mg morphine=1.5mg hydromorphone). There was essentially no difference between the groups' ages (41.0 for hydromorphone vs. 41.5 for morphine, p=0.84), initial pain scores (8.6 vs. 8.1, p=0.05), post-opioid pain scores (4.5 vs. 4.6, p=0.76), improvement in pain scores (4.1 vs. 3.5, p=0.10), proportion achieving 50% pain score reduction (55.9% vs. 49.8%, p=0.41), pain relief (3.3 for both on 1-5 scale), and overall patient satisfaction (4.6 vs. 4.7 on 1-6 scale, p=0.60). Though not significant, nearly 50% more hydromorphone patients experienced minor side effects (29.4% vs. 19.7%, p=0.10).

Conclusions: Non-equianalgesic prescribing of hydromorphone and morphine in emergency patients does not seem to produce disparate analgesic outcomes. In contrast to a recent study(3), our data suggest that 4mg of morphine (or equivalent) is a reasonable starting dose for ED patients with severe pain, provided that prompt reassessment and re-dosing occurs in the half of patients who fail to adequately respond to the initial dose.