SCAPE is a medical emergency that occurs when patients with acute congestive heart failure complicated with pulmonary edema present to the emergency department with markedly hypertension, severe dyspnea, and desaturation.
In this lecture, we will discuss the pathophysiology, clinical features, and management of SCAPE.
SCAPE is a result of a sympathetic surge mediated by activation of the renin-angiotensin-aldosterone system (RAAS).
The sympathetic surge results in high peripheral vascular resistance and increased sodium and water reabsorption, which worsen cardiac function and lead to pulmonary congestion, pulmonary edema, hypoxia, and further sympathetic surge.
SCAPE patients usually present to the emergency department with extreme respiratory distress associated with diaphoresis, restlessness, and high blood pressure (usually SBP above 180 mm Hg).
Life-threatening acute pulmonary edema may not be caused by fluid accumulation but rather fluid redistribution because of heart failure and increased systemic vascular resistance from sympathetic neurohormonal activation.
High doses of nitrates, combined with noninvasive positive pressure ventilation (NIPPV), such as BiPAP, are the mainstay of treatment of SCAPE, and should be started within minutes of the patient's arrival to the ED.
Diuretics are less helpful due to their later onset. High doses of nitroglycerin (NTG) are well tolerated. Recent studies demonstrated that high doses of NTG are more likely to induce nitrate tolerance than low doses of NTG.
When treated promptly, patients with SCAPE will recover rapidly.
Typically, 0.6 mg of sublingual NTG is given up to 3 times followed by 1-2 mg NTG intravenous boluses every 2 minutes as needed, up to 10-20 mg maximum.
Non-rebreather mask and BiPAP can be used to provide supplemental oxygen and positive pressure ventilation to patients receiving high-dose NTG.
This can help to improve oxygenation and ventilation, and buy time for the NTG to take effect.
Contraindications to NTG use include severe aortic stenosis, recent use of phosphodiesterase type 5 inhibitors, hypertrophic obstructive cardiomyopathy, or hypotension at any time.
Examples of phosphodiesterase type 5 inhibitors include sildenafil, tadalafil, and vardenafil.
In conclusion, SCAPE is a medical emergency that requires prompt recognition and management.
Clinicians must know how to manage SCAPE with high-dose nitrates and noninvasive positive pressure ventilation.
When treated promptly, one will not only save a life but also obviate the need for endotracheal intubation and ICU admission.