Should morphine dosing be weight based for analgesia in the emergency department?

Asad E. Patanwala, PharmD; Christopher J. Edwards, PharmD; Lori Stolz, MD; Richard Amini, MD; Amol Desai, MD; Uwe Stolz, PhD, MPH

doi:10.5055/jom.2012.0096

Authors

Asad E. Patanwala, PharmD
Christopher J. Edwards, PharmD
Lori Stolz, MD
Richard Amini, MD
Amol Desai, MD
Uwe Stolz, PhD, MPH

DOI:

https://doi.org/10.5055/jom.2012.0096

Keywords:

pain, morphine, emergency department

Abstract

Objective: To determine if patient weight is predictive of the degree of analgesic response to morphine in opioid naïve patients in the emergency department (ED).
Design: Prospective observational study.
Setting: Academic, tertiary ED, designated as a level 1 trauma center.
Patients: Fifty opioid naïve adult patients who were administered a single fixed intravenous dose of 4 mg morphine on initial presentation to the ED.
Interventions: Pain was assessed at baseline and then repeated at 15- and 30-minute postdose using an 11-point (0-10) verbal numerical rating scale (NRS).
Main outcome measures: The primary outcome was maximum analgesic response, which is defined as the difference between initial pain score and lowest pain score achieved postdose at 15 or 30 minutes. Linear regression was used to analyze the relationship between maximum pain reduction and patient weight.
Results: Mean patient weight was 85.4 kg (standard deviation= ±24.2; range 47.6-170). Median initial pain score was 8 (range 6-10) and median lowest pain score achieved postdose was 4 (range 0-10). In the linear regression analysis, patient weight did not predict the degree of pain reduction on the NRS (coefficient = 0.002 [95% confidence interval (CI)= −0.029-0.032], R2 <0.001, p = 0.91). The only variable predictive of the degree of pain reduction was initial pain score (coefficient = 0.537 [95% CI = 0.013-1.061], R2 = 0.081, p = 0.045).
Conclusions: Patient weight was not significantly associated with the degree of analgesic response to morphine in opioid naïve adults. Morphine dosing based on patient weight alone is not necessary in adults in the ED.

Author Biographies

Asad E. Patanwala, PharmD

Clinical Assistant Professor, Department of Pharmacy Practice and Science, College of Pharmacy, University of Arizona, Tucson, Arizona.

Christopher J. Edwards, PharmD

Clinical Pharmacist, Department of Pharmacy Services, University Medical Center, Tucson, Arizona.

Lori Stolz, MD

Resident, Department of Emergency Medicine, University of Arizona, Tucson, Arizona.

Richard Amini, MD

Resident, Department of Emergency Medicine, University of Arizona, Tucson, Arizona.

Amol Desai, MD

Resident, Department of Emergency Medicine, University of Arizona, Tucson, Arizona.

Uwe Stolz, PhD, MPH

Research Specialist, Department of Emergency Medicine, University of Arizona, Tucson, Arizona.

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