title: Association of delay to first intervention with return of spontaneous circulation in a swine model of cardiac arrest.
abstract: OBJECTIVE
  No single drug improves survival after cardiac arrest, despite success in animal studies. We sought to determine the duration of circulatory arrest after which maximal drug treatment and a rescue shock would fail to achieve return of spontaneous circulation (ROSC).
  
  
  METHODS
  Retrospective analysis of 271 swine (20-30 kg) resuscitation attempts during ventricular fibrillation. Protocols were divided into five categories: immediate countershock, cardiopulmonary resuscitation (CPR) with standard-dose drugs, CPR alone, CPR and high-dose epinephrine (CPR+HDE) (0.1 mg/kg), and CPR with a drug cocktail (CPR+DC) of propanolol (1 mg), epinephrine (adrenaline) (0.1 mg/kg) and vasopressin (40IU). Time to first CPR, time to first drug administration, time to first shock, and protocol were examined as predictors of ROSC using logistic regression with Hosmer-Lemeshow test of fit. Probability of ROSC was calculated from logistic curves.
  
  
  RESULTS
  ROSC occurred in 119 of the 271 swine (44%). Time to first drug and the CPR+DC group were predictors of ROSC. Time to first CPR, the CPR+DC group, and the CPR+HDE group were also predictors of ROSC. Time to first rescue shock, the CPR+DC group, and the CPR+HDE groups were predictors of ROSC. In the CPR+DC group, 50% ROSC occurred at a first CPR time of 13.4 min, first drug time of 14.1 min and first rescue shock time of 17.5 min.
  
  
  CONCLUSIONS
  Pre-shock delivery of CPR+DC increases the likelihood of ROSC, and reaches 50% with a time of drug delivery of 14.1 min. ROSC rates of 50% may be achievable using an optimized resuscitation in experimental CPR.
authors.affiliation: University of Pittsburgh, Department of Emergency Medicine, Pittsburgh, PA 15213, USA. rittenbergerjc@upmc.edu
authors.forename: Jon C
authors.initials: JC
authors.lastname: Rittenberger
authors.forename: James J
authors.initials: JJ
authors.lastname: Menegazzi
authors.forename: Clifton W
authors.initials: CW
authors.lastname: Callaway
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation; D003326:Coronary Circulation; D004338:Drug Combinations; D004554:Electric Countershock; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006324:Heart Arrest, Induced; D008297:Male; D023421:Models, Animal; D011433:Propranolol / Q000494:pharmacology; D020127:Recovery of Function; D012189:Retrospective Studies; D013552:Swine; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology; D014693:Ventricular Fibrillation / Q000628:therapy
chemical_list: D004338:Drug Combinations; D014662:Vasoconstrictor Agents; D014667:Vasopressins; D011433:Propranolol; D004837:Epinephrine