Narcan Effectiveness in ED Treatment of Heroin Overdoses

Recently published in the Acad. Emerg. Med. December 28, 2018

Most patients who overdose on opioids can be safely discharged from the emergency department (ED) as early as an hour after prehospital administration of the opioid antagonist naloxone, the study has found.

Opioid-related ED visits nearly doubled in the United States from 2005 to 2014. 

The researchers conducted a prospective study to validate the early discharge rule practiced at St. Paul's Hospital, Vancouver, Canada, which allows for discharge after 1 hour for those in whom the following six criteria are within normal limits: ambulation, oxygen saturation (> 95%), respiratory rate (>10 and <20 breaths/min), temperature (>35.0° C and <37.5° C), heart rate (>50 and <100 beats/min), and Glasgow Coma Scale score (15).

The study included 538 adult patients who presented by ambulance to the ED from 2016 to 2017, who had been administered at least one dose of naloxone before entering the hospital, and who underwent evaluation by an emergency medicine provider 1 hour after naloxone administration. (The typical observation period at the hospital is 4 hours.) The mean age of the patients was 33.4 years, and 69.5% were male.

The researchers examined whether clinical judgment, the St. Paul's Early Discharge Rule, or both, when utilized 1 hour after prehospital administration of naloxone, could predict who would have an adverse event (AE) within 24 hours.

AEs occurred in 82 patients (15.4%), but none died within 48 hours. The most common AEs were need for supplemental oxygen (11.3%), repeat naloxone for hypoventilation (3%), and assisted ventilation (2.6%).

Overall, the rule had a sensitivity of 84.1% (95% confidence interval [CI], 76.2 - 92.1), a specificity of 62.1% (95% CI, 57.6 - 66.5), and a negative predictive value of 95.6% (95% CI, 93.3 - 97.9). The inability to mobilize normally had the greatest sensitivity (58.0%) for predicting AEs; an abnormal temperature had the greatest specificity (99.1%). The rule failed to predict AEs in just 13 of 538 cases (2.4%).

These results are in line with the derivation study by the rule's originators, which found that the AE rate was 16% and the negative predictive value was 99%.

Only one patient in the study whose 1-hour evaluation results were normal subsequently needed additional naloxone following another presumed heroin overdose.

When used in tandem with healthcare provider judgment, the rule had a sensitivity of 87.8% (95% CI, 80.7% - 94.9%), a specificity of 53.0% (95% CI, 48.4% - 57.7%), and a negative predictive value of 96.0% (95% CI, 93.5 - 98.4%). Used together, provider judgment and the St. Paul's Early Discharge Rule predicted AEs in all but 10 of 529 patients (1.9%) .

 "Applying the prediction rule for patients for whom providers have a low clinical suspicion for AEs is a reasonable approach for risk stratifying patients for early discharge following naloxone administration for suspected opioid overdose," the authors write. They add, however, that the rule should be used with caution in cases of known oral or mixed overdose. They also call for further study to determine the rule's effectiveness in the context of overdoses of different drugs, drug combinations, and routes of administration.

Acad Emerg Med. Published online December 28, 2018. Full text

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