Safety and Feasibility of Prehospital Treatment of Acute Pulmonary Edema with Intravenous Bolus Nitroglycerin

Objective Prompt afterload reduction with high dose nitrates remains the cornerstone of treatment for decompensated heart failure with acute pulmonary edema (APE). Nitrate therapy in the prehospital setting is often limited to relatively low doses of sublingual nitroglycerin (NTG), which has poor bioavailability and is challenging to administer with concurrent use of non-invasive ventilation. Conversely, treatment in the Emergency Department typically consists of high doses of nitroglycerin, either by continuous intravenous (IV) infusion or by IV bolus (IVB NTG). A growing body of evidence suggests the safety and efficacy of large doses of IVB NTG in the hospital and prehospital settings. In this study, we assessed the safety and effectiveness of a prehospital bundle of care, which included IVB NTG followed by maintenance IV infusion of NTG for the treatment of decompensated heart failure with acute pulmonary edema. Methods This is a retrospective chart review of patients who received IVB NTG for decompensated heart failure with APE between May 1, 2019 and January 31, 2020 in a large, geographically diverse EMS system in Minnesota and Wisconsin. Inclusion criteria for treatment under this protocol included a working diagnosis of APE, a systolic blood pressure ≥120 mmHg and SpO2 ≤93% following 0.8 mg of SL NTG. Treatment consisted of a 400-mcg IV bolus of NTG, repeated every 2 minutes as needed during transport if SBP ≥120 mmHg. For transport times ≥10 minutes, an intravenous infusion of NTG was initiated at 80 mcg/min and titrated as needed to improve symptoms. Hypotension was defined as a systolic blood pressure ≤ 90 mmHg or a MAP ≤ 65 mmHg. Results During the study period, 45 patients were treated with IVB NTG. 25 patients were treated with IVB NTG alone. The median (IQR) total bolus dose was 400 mcg (400-1200 mcg). 20 patients were treated with a NTG infusion following IVB NTG. The median (IQR) infusion dose was 80 mcg/min (80-100 mcg/min). For all patients, the initial median (systolic IQR) blood pressure was 191/113 mmHg (169-217), 5 minutes following IVB NTG was 158/94 mmHg (141-178), and on arrival to the ED was 152/89 mmHg (129-172). 5 minutes after the initial dose of IVB NTG, there was an increase in median (IQR) oxygen saturation (SpO2) to 92% (88-96) from an initial reading of 88% (78-93). Median (IQR) SpO2 at hospital arrival was 94% (90-98). Median (IQR) transport time was 14 minutes (8.5-19). One episode of transient hypotension occurred during EMS transport and resolved without intervention. There were no cases requiring prehospital advanced airway management in this series. Conclusion Patients treated with IVB NTG by paramedics for APE had reduction in blood pressure and improvement in SpO2compared to their original presentation. There was one instance of transient hypotension that resolved without intervention en route. There were no cases requiring advanced airway management.