Nebulized Nitroglycerin Improves Carotid Blood Flow During Cardiopulmonary Resuscitation in a Swine Model of Cardiac Arrest.

Abstract

Objectives: Pulmonary vasodilators have shown promise in reducing pulmonary vascular resistance during CPR. Most are not currently available outside of an intensive care unit (ICU) setting. Nitroglycerin is widely used by emergency medical services to treat chest pain. If beneficial, the inhalation route of nitroglycerin administration could be implemented by basic life support personnel at the scene of a cardiac arrest. The aim of this investigation was to assess the hemodynamic effects of nebulized nitroglycerin (NIN) in a swine model of ventricular fibrillation (VF)-induced cardiac arrest.

Methods: Seventeen Mixed breed Yorkshire swine (54 + 5 kg) were anesthetized. Ventricular fibrillation was then induced by connecting a 9-volt battery to a pacing catheter in the right ventricle. After 7 minutes of untreated VF, mechanical chest compressions were initiated. Three minutes later, mechanical ventilation was resumed at pre-arrest settings with 100% FiO2. Two minutes later, 5 mL of normal saline (NIS controls, n = 9) or with 10 mg of nitroglycerin (NIN treatment, n = 8) were randomly nebulized through a nebulizer in line with the respiratory circuit. After 4 minutes of nebulization, an intravenous dose of epinephrine (0.015 mg/kg) was administered, followed 2 minutes later by defibrillation. Standard advanced cardiac life support resuscitation was continued along with NIN or NIS until full delivery, and continued until return of spontaneous circulation or 40 minutes had elapsed since arrest. Data were analyzed using mixed effects models.

Results: Prearrest arterial and right atrial pressures, chemistries and arterial blood gas values were similar between groups. There were no differences in systolic, diastolic, or coronary perfusion pressures. There was a statistically significant increase in carotid blood flow (CBF) following NIN. Before administering epinephrine, CBF in NIN-treated animals were approximately double those of NIS controls: 92.2 (95%CI 70.69-113.74) versus 41.96 (95% CI 22.28-61.63) mL/min, respectively, a mean difference of 50.26 mL/min (95% CI 24.91-75.61, p < 0.0001).

Conclusions: Early nebulized nitroglycerin treatment resulted in superior CBF without decreasing systemic arterial pressures or coronary perfusion pressures in this model of cardiac arrest.