The study describes the implementation of a prehospital treatment algorithm that included intravenous (IV) bolus (IVB) nitroglycerin (NTG) followed by maintenance infusion for the treatment of acute pulmonary edema (APE) in a single, high-volume Emergency Medical Services (EMS) system.

This is a retrospective chart review of patients who received IVB NTG for APE in a large EMS system in Minnesota and Wisconsin (USA). Inclusion criteria for treatment included a diagnosis of APE, systolic blood pressure ≥120mmHg, and oxygen saturation (SpO2) ≤93% following 800mcg of sublingual NTG. Patients received a 400mcg IVB of NTG, repeated every two minutes as needed, and subsequent infusion at 80mcg/min for transport times ≥10 minutes.

Forty-four patients were treated with IVB NTG. The median total bolus dose was 400mcg. Twenty patients were treated with NTG infusion following IVB NTG. The median infusion rate was 80mcg/min. For all patients, the initial median blood pressure was 191/113mmHg. Five minutes following IVB NTG, it was 160/94mmHg, and on arrival to the emergency department (ED) it was 152/90mmHg. Five minutes after the initial dose of IVB NTG, median SpO2 increased to 92% from an initial reading of 88% and was 94% at hospital arrival. One episode of transient hypotension occurred during EMS transport.

Patients treated with IVB NTG for APE had reduction in blood pressure and improvement in SpO2 compared to their original presentation. Prehospital treatment of APE with IVB appears to be feasible and safe. A randomized trial is needed to confirm these findings.

High-dose intravenous nitroglycerin is a common in-hospital treatment for respiratory distress due to congestive heart failure (CHF) with hypertension. Intravenous (IV) nitroglycerin administration is impractical in the prehospital setting. In 2011, a new regional Emergency Medical Services (EMS) protocol was introduced allowing advanced providers to treat CHF with high-dose oral nitroglycerin. The protocol calls for patients to be treated with two sublingual tabs (0.8 mg) when systolic blood pressure (SBP) was >160 mm Hg, or three sublingual tabs (1.2 mg) when SBP was >200 mm Hg, every five minutes as needed.

To assess the protocol's safety, the incidence of hypotension following prehospital administration of multiple simultaneous nitroglycerin (MSN) tabs by EMS providers was studied.

This study was a retrospective cohort study of patients from a single commercial EMS agency over a 6-month period. Records from patients with at least one administration of MSN were reviewed. For each administration, the first documented vital signs pre- and post-administration were compared. Administrations were excluded if pre- or post-administration vital signs were missing.

One hundred case-patients had at least one MSN administration by an advanced provider during the study period. Twenty-five case-patients were excluded due to incomplete vital signs. Seventy-five case-patients with 95 individual MSN administrations were included for analysis. There were 65 administrations of two tabs, 29 administrations of three tabs, and one administration of four tabs. The mean change in SBP following MSN was -14.7 mm Hg (SD = 30.7; range, +59 to -132). Three administrations had documented systolic hypotension in the post-administration vital signs (97/71, 78/50 and 66/47). All three patients were over 65 years old, were administered two tabs, had documented improved respiratory status, and had repeat SBP of at least 100. The incidence of hypotension following MSN administration was 3.2%.

High-dose oral nitroglycerin administration is a practical alternative to IV nitroglycerin in the prehospital setting when administered by advanced providers. The prehospital protocol for high dose oral nitroglycerin was demonstrated to be safe in the cohort of patients studied. Limitations of the study include the relatively small sample size and the inability to identify hypotension that may have occurred following the cessation of data collection in the field.

Hypotension was rare and self-limited in prehospital patients receiving MSN.

ClemencyB, ThompsonJ, TundoG, LindstromH. Prehospital High-dose Sublingual Nitroglycerin Rarely Causes Hypotension. Prehosp Disaster Med. 2013;28(5):1-4.

Heart failure poses a significant burden of disease, resulting in 2,658 Australian deaths in 2008, and listed as an associated cause of death in a further 14,466 cases. Common in the hospital setting, continuous positive airway pressure (CPAP) therapy is a non-invasive ventilation technique used to prevent airway collapse and manage acute pulmonary edema (APO). In the hospital setting, CPAP has been known to decrease the need for endotracheal intubation in patients with APO. Therefore the objective of this literature review was to identify the effectiveness of CPAP therapy in the prehospital environment.

A review of selected electronic medical databases (Cochrane, Medline, EMBASE, and CINAHL) was conducted from their commencement date through the end of May 2012. Inclusion criterion was any study type reporting the use of CPAP therapy in the prehospital environment, specifically in the treatment of heart failure and acute pulmonary edema. References of relevant articles were also reviewed.

The literature search located 1,253 articles, 12 of which met the inclusion criteria. The majority of studies found that the use of CPAP therapy in the prehospital environment is associated with reduced short-term mortality as well as reduced rates of endotracheal intubation. Continuous positive airway pressure therapy was also shown to improve patient vital signs during prehospital transport and reduce myocardial damage.

The studies conducted of prehospital use of CPAP to manage APO have all demonstrated improvement in patient outcomes in the short term.

Available evidence suggests that the use of CPAP therapy in the prehospital environment may be beneficial to patients with acute pulmonary edema as it can potentially decrease the need for endotracheal intubation, improve vital signs during transport to hospital, and improve short-term mortality.

WilliamsB, BoyleM, RobertsonN, GiddingsC. When Pressure is Positive: A Literature Review of the Prehospital Use of Continuous Positive Airway Pressure. Prehosp Disaster Med.2013;28(1):1-10.