Cardiovascular effects of epinephrine during neonatal cardiopulmonary resuscitation in a piglet model
Merlin Pinto1,2, Elliott Li2,3, Min Lu1,2,4, Tze-Fun Lee1,2, Megan O’Reilly1,2, Po-Yin Cheung1,2, Georg M. Schmölzer1,2
1Centre for the Studies of Asphyxia and Resuscitation, Neonatal Research Unit, Royal Alexandra Hospital, Edmonton, Canada
2Department of Pediatrics, University of Alberta, Edmonton, Canada
3Faculty of Science, McGill University, Montreal, Quebec, Canada
4Faculty of Science, University of Alberta, Edmonton, Alberta, Canada

Background
Neonatal resuscitation guidelines recommend epinephrine during cardiopulmonary resuscitation (CPR) to elevate the coronary perfusion pressure (CPP) to allow more oxygenated blood enter the coronary arteries to improve myocardial blood flow. However, no study has assessed the effects of epinephrine on cardiac function.

Objective: To determine cardiovascular effects of epinephrine administration during resuscitation of newborn piglets with asphyxia.

Materials and Methods:
Newborn piglets (n=8) were exposed to hypoxia and once bradycardia was achieved chest compression (CC) using 3:1 compression: ventilation ratio was started. Epinephrine was administered if heart rate remained < 60/min with a max of 4 doses until either return of spontaneous circulation (heart rate >150/min for 15s) or death. A Millar™ catheter (AD Instruments, Dunedin, New Zealand) was place and ejection fraction (EF). Measurements were taken at baseline (BL), during positive pressure ventilation, during CC, and after each epinephrine (Epi1-4) administration.

Results: Mean (SD) age of piglets was 2 (1) days and weight was 2037 (250)g. EF, mean arterial blood pressure (MAP) and dP/dt, but not CO or SV, significantly increased during CC and Epi1-4 (vs. BL). There were significant increases in MAP after Epi2 and dv/dt after Epi4, compared to BL values, while all other parameters were similar.

BL CC Epi 1-4
EF (%) 11 24 (p=0.048) 26-42 (p<0.02)
MAP (mmHg) 19 49 (p<0.001) 56-67 (p<0.001)
dP/dt (mmHg/s) 1144 3444 (p=0.002) 4066-9540 (p<0.002)


Conclusion: Epinephrine during neonatal CPR is in part is related to a vasoconstrictive action leading to increased MAP and thus CPP, which is important for the myocardial recovery following asphyxia in the newborn heart.