title: Resuscitation time limits in experimental pulseless electrical activity cardiac arrest using cardiopulmonary bypass.
abstract: OBJECTIVE
  The objective of this study was to determine the time limits of resuscitation following increasing intervals of untreated pulseless electrical activity using cardiopulmonary bypass as the resuscitation tool.
  
  
  METHODS
  Prospective controlled laboratory investigation using a canine model of pulseless electrical activity.
  
  
  METHODS
  20 mechanically ventilated mongrel dogs of either sex under Halothane anesthesia.
  
  
  METHODS
  Pulseless electrical activity was produced by clamping the endotracheal tube. The ECG and hemodynamics were monitored until loss of pressure fluctuations by aortic catheter. Animals were then randomized to remain in untreated pulseless electrical activity for 10 min (Group I), 15 min (Group II) or 20 min (Group III). Following each interval, resuscitation was begun using fixed-flow closed-chest cardiopulmonary bypass (50 ml/kg/min) and an epinephrine infusion (4 micrograms/kg/min). Cardiopulmonary bypass was continued for 30 min or until return of spontaneous circulation. Following return of spontaneous circulation, animals were weaned from bypass and observed for 1 h.
  
  
  RESULTS
  Return of spontaneous circulation was achieved in 100% (7/7) Group I, 50% (3/6) Group II and 29% (2/7) Group III animals (P < or = 0.02, Group I vs. Group III). One-hour survival was achieved in 71% (5/7) Group I, 33% (1/3) Group II and 0% (0/2) Group III animals (P > 0.05). Coronary perfusion pressure, bypass flow and arterial blood gases during reperfusion were similar between groups.
  
  
  CONCLUSIONS
  Cardiopulmonary bypass is effective at restoring spontaneous circulation when used early in asphyxial pulseless electrical activity cardiac arrest. Cardiopulmonary bypass is less effective when used after 15 min of pulseless electrical activity with no survivors following 20 min of arrest.
authors.affiliation: Department of Emergency Medicine, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: D
authors.initials: D
authors.lastname: DeBehnke
mesh_terms: D000818:Animals; D001237:Asphyxia / Q000150:complications; D002315:Cardiopulmonary Bypass / Q000379:methods; D004285:Dogs; D004562:Electrocardiography; D004837:Epinephrine / Q000627:therapeutic use; D005260:Female; D006323:Heart Arrest / Q000209:etiology / Q000401:mortality / Q000628:therapy*; D008297:Male; D012151:Resuscitation / Q000379:methods*; D013997:Time Factors
chemical_list: D004837:Epinephrine