The effects of endogenous and exogenous vasopressin during experimental cardiopulmonary resuscitation

Exogenous vasopressin is a promising vasopressor when blood pressure is cri tically threatened, but the role of endogenous vasopressin during cardiopul monary resuscitation (CPR) is unknown. We assessed the role of endogenous v ersus exogenous vasopressin in a porcine open chest CPR model. Seven minute s before induction of cardiac arrest, seven pigs received 10 mug/kg of a se lective vasopressin V-1-receptor-antagonist (Blocked Vasopressin group); an other 12 pigs in two groups received saline administration only. After 4 mi n of untreated ventricular fibrillation followed by 3 min of basic life sup port CPR, six animals received 0.8 U/kg vasopressin (Exogenous Vasopressin group), whereas the blocked vasopressin group (n = 7), and the remaining si x animals received saline placebo only (Endogenous Vasopressin group). Defi brillation was attempted after 14 min of CPR. During basic life support CPR , left ventricular myocardial blood flow was significantly (P < 0.05) decre ased in the Blocked Vasopressin group compared with the Exogenous Vasopress in group and Endogenous Vasopressin group (42 +/- 5 compared with 64 +/- 6 and 66 +/- 6 mL . min(-1) 100g(-1)). Left ventricular myocardial blood flow was significantly decreased in the Blocked Vasopressin group versus Exogen ous Vasopressin group versus Endogenous Vasopressin group 90 s and 5 min af ter drug administration, respectively (38 +/- 4 and 27 +/- 3 vs 145 +/- 32 and 110 +/- 12 vs 62 +/- 4 and 56 +/- 6 mL . min(-1) 100g(-1), respectively ). None of seven Blocked Vasopressin animals, six of six Exogenous Vasopres sin pigs, and six of six Endogenous Vasopressin swine had return of spontan eous circulation after 14 min of cardiac arrest including 10 min of CPR (P < 0.05). In conclusion, pigs with blocked endogenous vasopressin had poor c oronary perfusion pressure and left ventricular myocardial blood flow durin g open chest CPR, and could not be successfully resuscitated. All pigs with effective endogenous vasopressin or pigs with effective endogenous vasopre ssin and additional exogenous vasopressin had good left ventricular myocard ial blood flow during experimental CPR, and survived the l-h postresuscitat ion phase. We conclude that endogenous vasopressin is an adjunct vasopresso r to epinephrine and may serve as a back-up regulator to maintain cardiocir culatory homeostasis.