The effects of repeated doses of vasopressin or epinephrine on ventricularfibrillation in a porcine model of prolonged cardiopulmonary resuscitation

This study evaluated ventricular fibrillation mean frequency and amplitude to predict defibrillation success in a porcine cardiopulmonary resuscitatio n (CPR) model using repeated administration of vasopressin or epinephrine. After 4 min of cardiac arrest and 3 min of CPR, 10 pigs were randomly assig ned to receive either vasopressin (early vasopressin: 0.4, 0.4, and 0.8 uni ts/kg, respectively, n = 5) or epinephrine (early epinephrine: 45, 45, and 200 mu g/kg, respectively, n = 5). Another 11 animals were randomly allocat ed after 4 min of cardiac arrest and 8 min of CPR to receive every 5 min ei ther vasopressin (late vasopressin: 0.4 and 0.8 units/kg, respectively, n = 5) or epinephrine Gate epinephrine: 45 and 200 mu g/kg, n = 6). Ventricula r fibrillation mean frequency and amplitude on defibrillation were signific antly higher in the vasopressin groups than in the epinephrine groups, resp ectively. In vasopressin versus epinephrine animals, mean frequency immedia tely before defibrillation was 9.6 +/- 1.5 Hz vs 7.0 +/- 0.7 Hz (P < 0.001) , mean amplitude was 0.65 +/- 0.26 mV vs 0.21 +/- 0.14 mV (P < 0.001, and c oronary perfusion pressure was 27 +/- 9 mm Hg vs 8 +/- 4 mm Hg (P < 0.00001 ), respectively, in contrast to no epinephrine animals, all vasopressin ani mals were successfully defibrillated and survived 1 h (P < 0.05). Mean fibr illation frequency and amplitude predicted successful defibrillation and ma y serve as noninvasive markers to monitor continuing CPR efforts. Furthermo re, vasopressin was superior to epinephrine in maintaining these variables above a threshold necessary for successful defibrillation.