Journal Watch: Nitroglycerin for Acute Pulmonary Edema

Reviewed This Month

Feasibility, Effectiveness and Safety of Prehospital Intravenous Bolus Dose Nitroglycerin in Patients With Acute Pulmonary Edema

Authors: Patrick C, Ward B, Anderson J, et al.

Published in: Prehosp Emerg Care, 2020 Jan.

This month we review a manuscript that evaluates the use of a bolus dose of intravenous nitroglycerin for patients with decompensated congestive heart failure with acute pulmonary edema. As we know, it is vital that preload and afterload be reduced in these patients.

This is usually performed in the prehospital setting by administering sublingual nitroglycerin. However, sublingual administration of nitroglycerin does not typically provide a large enough dose to produce afterload-reducing effects. The authors of this study also note that noninvasive positive-pressure ventilation, such as CPAP, can complicate sublingual nitroglycerin administration. 

The authors found that previous studies performed in emergency departments showed an intravenous bolus dose of nitroglycerin decreases the need to intubate, ICU admission rates, and hospital lengths of stay in decompensated CHF patients with acute pulmonary edema. However, this had not previously been evaluated in the prehospital setting. 

Objective and Methodology

The objective of this study was to assess “the feasibility, effectiveness, and safety of prehospital IV bolus nitroglycerin use in decompensated congestive heart failure patients with acute pulmonary edema by paramedics within a single, high-volume ground-based EMS agency.”

This was a retrospective chart review. Charts were reviewed from March 15, 2018 to March 15, 2019. The authors reviewed all EMS and ED patient care records for patients that were treated for presumed decompensated congestive heart failure patients with acute pulmonary edema.

One of the more interesting parts of this study design is that it originated as a quality improvement project. There is a myth that QI projects cannot be published in peer-reviewed literature because they are not typical research. Important results should be published whether the project originated as traditional research or for quality improvement. 

One month prior to beginning this project, paramedics were required to complete a two-hour training session that reviewed nitroglycerin pharmacology as well as the pathophysiology and clinical findings among decompensated congestive heart failure patients with acute pulmonary edema. At the conclusion of this training, paramedics were required to pass written and psychomotor exams. 

Following the completion of training, the protocol for treatment of these patients gave the paramedics the option to administer 0.4 mg of sublingual nitroglycerin while IV or IO access was being obtained. Once access was obtained, an initial dose of 1 mg nitroglycerin was administered slowly and repeated in five minutes if the patient’s systolic blood pressure remained above 160 mmHg. The maximum total dose was 2 mg. 

The inclusion criteria for the chart review included a free text search of the electronic prehospital care reports for all patients administered an IV bolus of nitroglycerin and all patients who presented to EMS with dyspnea and a systolic blood pressure greater than 160 mmHg. Following examination of the EMS patient care report, hospital records were reviewed for all patients who were treated under the protocol. Charts were reviewed by two physicians and one paramedic. 

Results

There were 250 charts that met the inclusion criteria and were reviewed. Of those 162 (65%) were determined to not qualify because a diagnosis other than decompensated congestive heart failure with acute pulmonary edema (COPD, pneumonia) was likely.

There were 88 patients who were identified as having decompensated congestive heart failure with acute pulmonary edema. Of those, 18 (20%) had neither an IV placed nor an IO attempted, and 22 (25%) were untreated because of a paramedic’s decision not to administer the IV bolus of nitroglycerin. There were 48 patients identified that were treated under the protocol. 

These patients had a mean age of 70 and were mostly male and white, with a past medical history including hypertension and congestive heart failure. Median scene and transport times for these patients were similar to overall EMS system times. Of the patients treated with bolus dose IV nitroglycerin, 33 (69%) received a single 1-mg dose, and 15 (31%) received a second 1-mg dose.

Prior to treatment with the bolus dose of IV nitroglycerin, 16 patients (33%) received sublingual nitroglycerin, 42 (88%) of the patients were maintained on noninvasive positive-pressure ventilation, and 4 (8%) required prehospital intubation. There were 14 (29%) who received albuterol. 

Patients treated with the IV bolus of nitroglycerin had a median initial SBP of 211 mmHg. This was reduced to 177 mmHg in five minutes post-nitroglycerin administration. Median pulse decreased from 113 to 103 beats per minute, and median oxygen saturation increased from 86% to 98%. In total, 41 (85%) of the 48 patients treated had improvements in SBP, and 45 (94%) had improvements in oxygen saturation.

One patient had hypotension following a 1-mg dose of nitroglycerin. However, the patient was normotensive on arrival at the ED without additional treatment. This patient had no additional adverse events. The review of hospital records revealed that 45 (94%) of the treated patients were diagnosed with decompensated congestive heart failure with acute pulmonary edema. 

Limitations and Lessons

There are limitations as with every study. Along with the retrospective design, this study was limited by a small sample size. A cohort of 48 patients would not be sufficient for a typical research study. However, as we discussed earlier, this project originated as a QI study. QI studies are not meant to wait for perfect data.

This study found that in this EMS system, a bolus of IV nitroglycerin was feasible, safe, and effective. This may not be true for all EMS systems. However, this study can be the impetus for a randomized, large-scale study. 

This study highlights that QI studies can and should be published. I am sure many of you have found some amazing results from QI studies you have performed in your systems. This study shows that if your QI study generates results that can advance our field, publication is not out of the question. So, write that manuscript and submit it for peer review!  

Antonio R. Fernandez, PhD, NRP, FAHA, is a research scientist at ESO and an assistant professor in the department of emergency medicine at the University of North Carolina–Chapel Hill. He is on the board of advisors of the Prehospital Care Research Forum at UCLA.