Prearrest administration of low-molecular-weight heparin in porcine cardiac arrest: hemodynamic effects and resuscitability.

Abstract

Both animal and human studies demonstrate activation of coagulation during cardiac arrest. Prearrest anticoagulation is used routinely in many experimental studies. We studied the hemodynamic effects of prearrest anticoagulation with a low-molecular-weight heparin suitable for clinical use during cardiopulmonary resuscitation in pigs. Randomized and blinded experimental animal study. University hospital-affiliated research laboratory. Sixteen female domestic pigs. Three minutes before electrically induced ventricular fibrillation, enoxaparin 1 mg/kg or physiologic saline was blinded and administered intravenously. After 10 mins of untreated ventricular fibrillation, advanced cardiac life support was initiated with continuous mechanical chest compressions and interposed manual ventilation with 100% oxygen. Epinephrine was administered after 2 mins of advanced cardiac life support followed by attempted defibrillation 1 min thereafter. Advanced cardiac life support was continued for 10 mins following international guidelines. Electrocardiogram was recorded continuously and ventricular fibrillation waveform was analyzed (median slope). Animals with return of spontaneous circulation were observed for ten more minutes. Blood specimens were drawn for analysis of coagulation activation (thrombin-antithrombin complex) and drug effect (anti-factor Xa activity). Six of eight (75%) pigs in each group achieved return of spontaneous circulation. Thrombin-antithrombin complex levels were significantly lower in pigs that received enoxaparin. There was no significant difference either in measured hemodynamics between the groups during advanced cardiac life support and after return of spontaneous circulation or in median slope values during ventricular fibrillation. Epinephrine caused a significant decrease in femoral and increase in cerebral cortical blood flow with no difference between the groups. Prearrest anticoagulation with enoxaparin did not influence either hemodynamics during advanced cardiac life support and after return of spontaneous circulation or the frequency of return of spontaneous circulation in porcine cardiac arrest.