A 70-year-old woman is brought to the emergency department by ambulance due to the abrupt … — USMLE Step 2 CK

A 70-year-old woman is brought to the emergency department by ambulance due to the abrupt onset of severe shortness of breath that began 45 minutes ago while she was watching television. She has a history of severe chronic obstructive pulmonary disease (COPD), hypertension, and a myocardial infarction 3 years ago. She appears extremely anxious, diaphoretic, and is speaking in one-word sentences. Vital signs are temperature $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure $225/115\text{ mmHg}$ , pulse $118\text{/min}$ , and respirations $32\text{/min}$ . Oxygen saturation is $85\%$ on room air.

Physical examination shows prominent use of accessory muscles of respiration. Lung auscultation reveals diffuse high-pitched expiratory wheezing bilaterally and bibasilar crackles. Cardiac auscultation reveals an $S_4$ gallop. There is no jugular venous distension or peripheral edema.

Arterial blood gas on room air reveals:
- pH: $7.25$
- $\text{pCO}_2$ : $65\text{ mmHg}$
- $\text{pO}_2$ : $50\text{ mmHg}$
- $\text{HCO}_3^-$ : $28\text{ mEq/L}$

Which of the following is the most appropriate initial management for this patient?

Noninvasive positive-pressure ventilation and intravenous nitroglycerinAnswer
B
Nebulized ipratropium-albuterol and intravenous methylprednisolone
C
Intravenous furosemide and supplemental oxygen via nasal cannula
D
Intravenous levofloxacin and intravenous methylprednisolone
E
Intravenous sodium bicarbonate and endotracheal intubation

Answer

Noninvasive positive-pressure ventilation and intravenous nitroglycerin

This patient is presenting with Sympathetic Crashing Acute Pulmonary Edema (SCAPE), a severe phenotype of acute decompensated heart failure. SCAPE is characterized by the abrupt onset (minutes to hours) of extreme dyspnea, flash pulmonary edema, and severe hypertension resulting from a sympathetic surge and massive afterload increase. Unlike classic heart failure exacerbations, these patients are often euvolemic (no peripheral edema or JVD) but suffer from rapid fluid redistribution from the systemic circulation into the pulmonary vasculature. The prominent wheezing ('cardiac asthma') and history of COPD can mislead clinicians into diagnosing a COPD exacerbation. However, the extreme hypertension, acute onset, and

S_4

gallop strongly point to a cardiac etiology. The most appropriate initial management is rapid afterload reduction with high-dose intravenous nitroglycerin and noninvasive positive-pressure ventilation (NIPPV). NIPPV decreases left ventricular transmural pressure (reducing afterload), decreases venous return (reducing preload), and directly treats hypoxemia and the work of breathing.

Step-by-Step Solution

Analyze the clinical presentation and temporal onset.

The patient has abrupt onset (45 minutes) of severe dyspnea, extreme hypertension (225/115 mmHg), and flash pulmonary edema without peripheral edema.

Differentiates Sympathetic Crashing Acute Pulmonary Edema (SCAPE) from a typical gradual COPD exacerbation or volume-overload heart failure.

Interpret the physical exam findings.

Wheezing with bibasilar crackles and an S4 gallop indicates 'cardiac asthma' secondary to acute elevated left ventricular end-diastolic pressure, not isolated bronchospasm.

Identifies the cardiac etiology of the respiratory distress despite the history of COPD.

Evaluate the arterial blood gas results.

pH 7.25 and pCO2 65 mmHg indicate acute respiratory acidosis with severe hypoxemia.

Confirms the need for immediate ventilatory support.

Determine the most appropriate initial interventions.

Select interventions that rapidly decrease afterload and support ventilation without intubation if possible.

Intravenous nitroglycerin causes rapid vasodilation (reducing afterload and preload), while NIPPV improves oxygenation and decreases work of breathing.

Key Concept

Management of Sympathetic Crashing Acute Pulmonary Edema (SCAPE)

Estimated Time:1m 30s

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