Predictors of pain relief and adverse events in patients receiving opioids in a prehospital setting

Am J Emerg Med. 2011 Jun;29(5):512-7. doi: 10.1016/j.ajem.2009.12.005. Epub 2010 Mar 26.


Objective: The aim of the study was to analyze factors predicting pain relief and adverse events in patients receiving opioids for acute pain in a prehospital setting.

Methods: In this prospective, observational clinical study, adult patients with a numerical rating scale (NRS) score of 5 of 10 or higher who required treatment with intravenous opioids for pain control were included. The primary outcome variable was final analgesia defined by an NRS score of 3 of 10 or lower upon arrival to the emergency department. Univariable and multivariable analyses were performed to identify predictive factors of pain relief and adverse effects.

Results: In total, 277 patients (age, 49 ± 22 years), 205 (74%) of whom were male and 154 (56%) with a traumatic pain were included in the analysis. Median (interquartile range) NRS scores at baseline and at discharge were 8 of 10 (7-10) and 3 of 10 (2-5), respectively. The final model had 3 independent variables reaching significance. Physician-staffed ambulance transportation (odds ratio [OR], 2.42; 95% confidence interval [CI], 1.07-5.49) was the only independent predictor of patients' final pain relief. High initial pain scores and acetaminophen use were predictive factors for failure of analgesia (OR, 0.79; 95% CI, 0.68-0.93 for one unit/10; P < .01; and OR, 0.40; 95% CI, 0.21-0.77; P < .01, respectively). In the entire sample, 25 (9.0%) presented one adverse effect, all mild to moderate in severity, with no significant predictive factors.

Conclusion: Despite advancement in prehospital pain management, pain relief at discharge is still inadequate in some patients. Finally, one important message of our study is that patients in pain have to be transported by well-equipped and staffed ambulances to reevaluate and alleviate pain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetaminophen / therapeutic use
  • Adult
  • Aged
  • Ambulances
  • Analgesics, Non-Narcotic / therapeutic use
  • Analgesics, Opioid / administration & dosage
  • Analgesics, Opioid / adverse effects*
  • Analgesics, Opioid / therapeutic use
  • Confidence Intervals
  • Emergency Medical Services* / statistics & numerical data
  • Female
  • Humans
  • Logistic Models
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Odds Ratio
  • Pain / drug therapy*
  • Pain Measurement
  • Prospective Studies
  • Treatment Failure


  • Analgesics, Non-Narcotic
  • Analgesics, Opioid
  • Acetaminophen