Does prearrest adrenergic integrity affect pressor response? A comparison of epinephrine and vasopressin in a spontaneous ventricular fibrillation swine model

ObjectivesCoronary perfusion pressure (CPP) during resuscitation from cardiac arrest has been shown to correlate with return of spontaneous circulation. Adrenergic blockade of beta-1 and alpha-1 receptors is common in the long-term management of ischemic heart disease and congestive heart failure. We sought to compare the CPP response to vasopressin vs. epinephrine in a swine model of cardiac arrest following pre-arrest adrenergic blockade.MethodsEight anesthetized and instrumented swine were administered 0.1 mg epinephrine and arterial pressure and heart rate response were measured. An infusion of labetalol was then initiated and animals periodically challenged with epinephrine until adrenergic blockade was confirmed. The left anterior descending coronary artery was occluded to produce ventricular fibrillation (VF). After 7 min of untreated VF, mechanical chest compressions were initiated. After 1 min of compressions, 1 mg epinephrine was given while CPP was recorded. When CPP values had returned to pre-epinephrine levels, 40 U of bolus vasopressin was given. Differences in CPP (post-vasopressor–pre-vasopressor) were compared within animals for the epinephrine and vasopressin response and with eight, non-adrenergically blocked, historical controls using Bayesian statistics with a non-informative prior.ResultsThe CPP response following epinephrine was 15.1 mmHg lower in adrenergically blocked animals compared to non-adrenergically blocked animals (95% Highest Posterior Density [HPD] 2.9–27.2 mmHg lower). CPP went up 18.4 mmHg more following vasopressin when compared to epinephrine (95% HPD 8.2–29.1 mmHg). The posterior probability of a higher CPP response from vasopressin (vs. epinephrine) in these animals was 0.999.ConclusionsPre-arrest adrenergic blockade blunts the CPP response to epinephrine. Superior augmentation of CPP is attained with vasopressin under these conditions.