Outcomes by rescue shock number during the metabolic phase of porcine ventricular fibrillation resuscitation.
BACKGROUND
Optimal resuscitation duration before the first rescue shock (RS) to maximize the probability of success after prolonged ventricular fibrillation (VF) cardiac arrest remains unknown. The purpose of this study was to determine the occurrence of return of spontaneous circulation (ROSC) and survival by RS attempt after 12 minutes of untreated VF.


METHODS
This was a secondary analysis of prospectively collected data from an institutional animal care and use committee-approved protocol. Fifty-three swine (30-35 kg) were instrumented under anesthesia. Ventricular fibrillation was electrically induced. After 12 minutes of untreated VF, cardiopulmonary resuscitation (CPR) was initiated (and continued as necessary (prn)) and a standard dose of epinephrine (0.01 mg/kg) was given (and repeated every 3 (q3) minutes prn). The first RS was delivered after 3 minutes of CPR (and q3 minutes thereafter prn). Each failed RS was followed (in series) by vasopressin (0.57 mg/kg), amiodarone (4.3 mg/kg), and sodium bicarbonate (1 mEq/kg) prn. Resuscitation continued until ROSC or 20-minute elapsed time. The primary outcomes were ROSC and 20-minute survival. Data were analyzed using descriptive statistics.


RESULTS
After 3 minutes of resuscitation, 1 animal (1.9% [95% confidence interval {CI, 0.3-10.0]) achieved ROSC on RS1 and survived. After 6 minutes of resuscitation, 17 animals (32.1% [95% CI, 21.1-45.5]) achieved ROSC on RS2 and 15 (28.3% [95% CI, 18.0-41.6]) survived. Twelve additional animals had ROSC and survival with continued resuscitation. In 23 animals, ROSC was never achieved and efforts were terminated per protocol.


CONCLUSIONS
Our data suggest that during the metabolic phase of VF, 3 minutes of CPR and 1 standard dose of epinephrine may be insufficient to achieve ROSC on the first RS attempt. A longer duration of CPR and/or additional vasopressors may increase the likelihood of successful defibrillation.
Kansas City University of Medicine and Biosciences, Kansas City, MO.
Ryan A
RA
Coute
Department of Emergency Medicine, Baystate Medical Center/Tufts University School of Medicine, Springfield, MA. Electronic address: timothy.mader@baystatehealth.org.
Timothy J
TJ
Mader
Departments of Medicine and Bioengineering, University of Washington School of Medicine, Seattle, WA; Department of Emergency Medicine at St Francis Hospital, Federal Way, WA.
Lawrence D
LD
Sherman
D000818:Animals; D001775:Blood Circulation / Q000502:physiology; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D002985:Clinical Protocols; D004195:Disease Models, Animal; D005260:Female; D012770:Shock, Cardiogenic / Q000503:physiopathology / Q000628:therapy; D013552:Swine; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*