Resus: Diagnosis and Management of Sympathetic Crashing Acute Pulmonary Edema (SCAPE)
Sympathetic Crashing Acute Pulmonary Edema (SCAPE) formerly called “flash pulmonary edema” and sometimes called “hypertensive acute heart failure” is a subset of acute heart failure that results in rapid onset tachypnea and dyspnea. SCAPE occurs due to uncontrolled sympathetic function and severe vasoconstriction resulting in increased afterload and hypertension1. This article will review the clinical presentation and diagnostic criteria, differential diagnoses, and management of SCAPE.
Clinical Presentation & Diagnosis:
Patients with SCAPE will experience tachypnea and dyspnea that onset rapidly within a few hours and are accompanied by severe hypoxemia1. Patients will also have vital sign abnormalities including hypertension, often SBP > 160 and / or DBP > 120, and tachycardia due to the sympathetic drive1. They often have diffuse rales on pulmonary exam and may have frothy sputum2.
POCUS is an incredible diagnostic tool for making the diagnosis of SCAPE. Lung POCUS will demonstrate B-lines throughout the chest in SCAPE1,2. If there are no diffuse B-lines, SCAPE can be confidently excluded as the cause of dyspnea2. Cardiac POCUS may demonstrate findings consistent with heart failure such as decreased EF or ventricular hypertrophy2. Finally, patients with SCAPE can have variable volume status— they can be hypovolemic, euvolemic, or hypervolemic 1,2. Therefore, the patient may not have signs of gross volume overload that might otherwise be associated with a heart failure exacerbation such as a distended IVC or peripheral edema. Chest x-rays may be useful, demonstrating interstitial edema and sometimes pleural effusions. However, some patients with SCAPE can have a normal x-ray1, making POCUS the best diagnostic tool in this case.
Patients with SCAPE may have troponinemia and ECG should be obtained to ensure that there is no underlying acute coronary syndrome1. However, troponinemia is most likely to be related to a Type 2 MI from demand ischemia1.
Image from emcrit.org, “Sympathetic Crashing Acute Pulmonary Edema (SCAPE)” by Josh Farkas, accessed 1/29/2025.
Differential Diagnosis
The differential diagnoses for patients presenting with hypertension, tachypnea, and dyspnea is broad and the management strategies for each vary considerably. Listed below are a few notable mimics.
Asthma exacerbation:
Patients with an asthma exacerbation may present with dyspnea and vital sign abnormalities such as hypoxemia, hypertension, and tachycardia— just like in SCAPE.
However, the physical exam is critical as patients with an asthma exacerbation will not have diffuse rales or B-lines on ultrasound.
Utilize POCUS quickly to assess for pulmonary edema.
Importantly, while patients with an acute asthma exacerbation should be administered epinephrine, patients with SCAPE will get worse with epinephrine due to the increased sympathetic drive.
ARDS
ARDS is respiratory failure characterized by non-cardiogenic pulmonary edema and hypoxemia3. ARDS is driven by an inflammatory process rather than by sympathetic activation as is the case with SCAPE.
ARDS is not associated with hypertension, but patients with ARDS can still be hypertensive.
Patients with SCAPE should respond very rapidly to interventions, which will be discussed below. If patients do not respond to interventions, reconsider ARDS2.
Fluid Overload with Subacute Pulmonary Edema
Patients with subacute pulmonary edema may present with dyspnea and vital sign abnormalities, but their symptoms onset more gradually and the patient is not often critically ill1.
Patients with subacute pulmonary edema can still develop SCAPE2.
Patients usually do not need positive airway pressure with subacute pulmonary edema but are typically hypervolemic and the key intervention for therapy is diuresis2.
Management of SCAPE
Patients with SCAPE should immediately be provided respiratory support with CPAP or BiPAP starting at a low pressure and escalating rapidly as tolerated if the patient remains distressed, to a maximum of 20 cm H2O1,2. If the patient resists ventilation, consider haloperidol, ketamine, or fentanyl for comfort1,2. If the patient continues to decompensate, progress to intubation.
The other mainstay of treatment in patients with SCAPE is high-dose nitroglycerin. The appropriate dosage of nitroglycerin is debated in the literature, though it is generally accepted that high-dose nitroglycerin is safe and superior to low-dose nitroglycerin1,2,4,5. A recent randomized controlled trial in India, performed in 2023, has supported this theory. The trial included 54 patients randomized to either high-dose nitroglycerin (600-1000 microgram boluses followed by a 100 microgram per minute infusion) or low-dose nitroglycerin (20-40 micrograms per minute without bolus) and the high-dose group had significantly improved outcomes including shorter hospital stays, fewer cardiovascular events, and lower intubation rates4. Other studies have found that even larger doses of nitroglycerin can be safe1,4-7.
A comprehensive review by Long et al. published in 2025 recommends:
A bolus of 500-1000 micrograms over 2 minutes followed by an infusion of 100-200 micrograms per minute.
If the patient is not responsive to these doses or SBP does not decrease to less than 160 mmHg, nitroglycerin can be up titrated further to 800 mcg/min, or bolus dosing can be repeated.
If still not responsive to therapy, re-assess possible differential diagnoses and / or consider other medications such as calcium channel blockers.
Volume removal with either loop diuretics or dialysis may be appropriate if the patient appears hypervolemic once SBP is controlled1.
AUTHORED BY: MEGAN CALLAGHAN, MS4
FACULTY EDITING BY: COLIN MCCLOSKEY, MD
References
Long B, Brady WJ, Gottlieb M. Emergency medicine updates: Sympathetic crashing acute pulmonary edema. Am J Emerg Med. Published online January 5, 2025. doi: 10.1016/j.ajem.2024.12.061. Available on PubMed: https://pubmed.ncbi.nlm.nih.gov/39799613/
Farkas, J. Sympathetic crashing acute pulmonary edema (SCAPE). EMCrit. Published August 30, 2021. Accessed January 29, 2025. https://emcrit.org/ibcc/scape/
Matthay MA, Zemans RL, Zimmerman GA, et al. acute respiratory distress syndrome. Nat Rev Dis Primers. 2019;5(1):18. Published 2019 Mar 14. doi:10.1038/s41572-019-0069-0. Available on PubMed: https://pubmed.ncbi.nlm.nih.gov/30872586/
Siddiqua N, Mathew R, Sahu AK, et al. High-dose versus low-dose intravenous nitroglycerine for sympathetic crashing acute pulmonary edema: a randomised controlled trial. Emerg Med J. 2024; 41:96-102. doi:10.1136/emermed-2023-123456. Available on PubMed: https://pubmed.ncbi.nlm.nih.gov/38050078/
Houseman BS, Martinelli AN, Oliver WD, Devabhakthuni S, Mattu A. High-dose nitroglycerin infusion: description of safety and efficacy in sympathetic crashing acute pulmonary edema: The HI-DOSE SCAPE study. Am J Emerg Med.2023; 63:74-78. doi: 10.1016/j.ajem.2022.10.018. Available on PubMed: https://pubmed.ncbi.nlm.nih.gov/36327753/
Wang K, Samai K. Role of high-dose intravenous nitrates in hypertensive acute heart failure. Am J Emerg Med. 2020;38(1):132-137. doi: 10.1016/j.ajem.2019.06.046. Available on PubMed: https://pubmed.ncbi.nlm.nih.gov/31327485/
Stemple K, DeWitt KM, Porter BA, Sheeser M, Blohm E, Bisanzo M. High-dose nitroglycerin infusion for the management of sympathetic crashing acute pulmonary edema (SCAPE): A case series. Am J Emerg Med. 2021; 44:262-266. doi: 10.1016/j.ajem.2020.03.062. Available on PubMed: https://pubmed.ncbi.nlm.nih.gov/32278569/