Abstract 71: A Novel Animal Model of Pulseless Electrical Activity Cardiac Arrest: Adrenergic Blockade and Coronary Occlusion

Introduction: The incidence of VF as the first documented rhythm in out-of-hospital cardiac arrest (OOHCA) has been declining, while the incidence of pulseless electrical activity (PEA) has been increasing. The increasing proportion of PEA as the initial rhythm for OOHCA has paralleled the increasing use of adrenergic antagonist therapy in the population most at risk for cardiac arrest. We hypothesized that PEA cardiac arrest can result from acute coronary occlusion in the setting of pre-arrest adrenergic blockade. Methods: Twenty-six anesthetized and instrumented immature male swine (mean weight 36 kg) were pre-treated with an infusion of labetalol, a β-1 and α-1 adrenergic blocker (mean dose 6 ± 3 mg/kg). Adequacy of adrenergic blockade was determined using an intravenous challenge of epinephrine 0.1 mg IV. After challenge and return to baseline, balloon occlusion of the left anterior descending (LAD) or proximal right coronary artery (RCA) was performed and the rhythm and hemodynamic response observed during sustained occlusion. Results: Occlusion of the RCA was followed by PEA or pseudo-PEA (defined as an organized rhythm with systolic arterial pressure <50 mm Hg) in 10/13 animals (77%). During RCA occlusion, cooling of the vagus nerve (reversible thermal vagotomy) did not prevent the hypotensive hemodynamic response. LAD occlusion was followed by PEA in 6/13 animals (46%). Brief occlusion of the RCA followed by occlusion of the LAD was followed by PEA in 5/7 animals (71%). Conclusions: Adrenergic blockade followed by coronary occlusion may be followed by PEA. This combination may play a role in the declining incidence of VF as the initial cardiac arrest rhythm in out-of-hospital cardiac arrest.