BET 2: Usefulness of epinephrine in out-of-hospital cardiac arrest

Administration of epinephrine by advanced emergency medical technicians for out-of-hospital cardiac arrest in a rural emergency medical services system

OBJECTIVE

Epinephrine in out-of-hospital cardiac arrest (OHCA) remains controversial and understudied in rural emergency medical services (EMS) systems. We evaluated the effects of allowing advanced emergency medical technicians (AEMTs) to administer epinephrine during OHCA in a rural EMS system.

METHODS

An interrupted time series study was conducted using statewide EMS electronic records. Patients with OHCA before (phase I) and after (phase II) a protocol change expanding the AEMT scope of practice to include epinephrine for OHCA were identified. Number and timing of initial epinephrine administration, return of spontaneous circulation, and 30-day survival rates were compared using descriptive statistics, logistic regression, regression discontinuity, and propensity score matching.

RESULTS

A total of 1037 OHCAs met the inclusion criteria. In phase 1 compared with phase 2, 275 (56.12%) patients received epinephrine versus 624 (83.53%; P < 0.001). The mean time to first administration of epinephrine for unwitnessed and bystander-witnessed OHCA were 11.73 minutes versus 8.17 minutes (P < 0.001) and 11.59 minutes versus 8.85 minutes (P < 0.01), respectively. Unadjusted analysis showed a decrease in 30-day survival rates among patients receiving epinephrine from 18.01% to 12.66% (P < 0.05). Adjusted analysis showed an increase in 30-day survival with decreased time to first epinephrine dose(OR 0.960, 1.005; 95% confidence interval, 0.929, 0.992).

CONCLUSION

Adding epinephrine for OHCA to the AEMT scope of practice was associated with an increased percentage of patients receiving epinephrine and decreased time to first administration of epinephrine for patients with unwitnessed OHCA. Unadjusted analysis showed a decrease in 30-day survival rates among patients receiving epinephrine. Adjusted analysis found that earlier administrationof epinephrine was associated with increased ROSC and 30-day survival.

Can epinephrine therapy be detrimental to patients with hypertrophic cardiomyopathy with hypotension or cardiac arrest? A systematic review

Approximately 10% of sudden cardiac deaths among patients under 35 years of age is owing to hypertrophic cardiomyopathy (HCM)-related cardiac arrest (CA). CA is often associated with pre-arrest or peri-arrest hypotension and is treated by a set of interventions, including the administration of epinephrine. It is debated whether epinephrine increases or decreases survival to discharge following CA. HCM is associated with septal hypertrophy with a dynamic left ventricular outflow tract obstruction and impaired peripheral vasoconstriction in response to α1-adrenergic stimulation, both of which could cause epinephrine to have a different effect than in the general population. This systematic review of the literature aimed to investigate if patients with HCM in CA have a detrimental hemodynamic response to epinephrine. A literature search was performed in October 2016 using Medline (OVID), Embase (Elsevier), and Cochrane Library (Wiley). The initial search generated 2429 articles, of which 22 articles were found to meet inclusion criteria: four physiology studies, 13 case reports of hypotensive HCM patients, and five case reports of HCM patients in CA. The reviewed studies demonstrate that epinephrine effect varies in patients with HCM: in some cases, the expected hypertensive effect was obtained, but in others, a paradoxical hypotensive effect, or no effect, was observed. The probable mechanism of this effect is an increased left ventricular outflow tract obstruction. Other drugs were considered in several of these cases. In summary, the retrieved studies jointly suggest that patients with HCM may respond differently to epinephrine than patients without HCM. The suitability of epinephrine in HCM-associated CA is questionable.