A 73-year-old woman is brought to the emergency department at 3:00 AM due to the sudden on… — USMLE Step 2 CK

A $73$ -year-old woman is brought to the emergency department at 3:00 AM due to the sudden onset of severe shortness of breath. She reports waking up from sleep feeling as though she were suffocating. Her medical history is significant for hypertension, coronary artery disease, and a $40$ -pack-year smoking history for which she takes a daily fluticasone-salmeterol inhaler. She has not had any recent fever, chills, or changes in sputum production.

On arrival, the patient is diaphoretic, anxious, and speaking in short, two-word phrases. She is sitting upright on the edge of the stretcher.

Vital signs are:
- Temperature: $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ )
- Blood pressure: $175/100\text{ mmHg}$
- Pulse: $118/\text{min}$ and regular
- Respirations: $28/\text{min}$
- SpO $_2$ : $84\%$ on room air

Physical examination reveals jugular venous distention up to $9\text{ cm H}_2\text{O}$ . Cardiac auscultation reveals a regular tachycardia with a prominent S3 gallop, and the point of maximal impulse is displaced lateral to the midclavicular line. Pulmonary auscultation demonstrates diffuse, bilateral expiratory wheezing and fine inspiratory crackles at the lung bases. There is bilateral trace pitting edema of the lower extremities.

Arterial blood gas analysis on room air reveals:
- $\text{pH}$ : $7.26$
- $\text{PaCO}_2$ : $58\text{ mmHg}$
- $\text{PaO}_2$ : $52\text{ mmHg}$
- $\text{HCO}_3^-$ : $25\text{ mEq/L}$

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

Intravenous furosemideAnswer
B
Intravenous methylprednisolone
C
Continuous nebulized albuterol
D
Intravenous sodium bicarbonate
E
Intravenous levofloxacin

Answer

Intravenous furosemide

The correct answer is intravenous furosemide. This patient is experiencing acute decompensated heart failure (ADHF) presenting with acute pulmonary edema. Although she has a history of smoking and uses inhalers, her paroxysmal nocturnal dyspnea, jugular venous distention, S3 gallop, laterally displaced point of maximal impulse, and bibasilar crackles are hallmark signs of left-sided heart failure and volume overload. The wheezing is a result of peribronchial edema compressing the small airways, a phenomenon often referred to as 'cardiac asthma.' The primary initial pharmacologic therapy for ADHF is rapid preload reduction, typically achieved with intravenous loop diuretics (e.g., furosemide) and vasodilators (e.g., nitroglycerin). This reduces pulmonary capillary hydrostatic pressure, allowing fluid to mobilize out of the alveolar spaces and improving oxygenation and ventilation.

Step-by-Step Solution

Analyze the clinical presentation to identify the primary syndrome.

The patient has paroxysmal nocturnal dyspnea, severe hypoxemia, JVD, an S3 gallop, and a laterally displaced PMI.

These findings are classic signs of volume overload and acute decompensated heart failure (ADHF) causing cardiogenic pulmonary edema.

Differentiate the cause of the wheezing from primary pulmonary etiologies.

Despite the smoking history and inhaler use, the wheezing is accompanied by signs of left-sided heart failure (S3, crackles) and right-sided pressures (JVD).

This presentation is consistent with 'cardiac asthma', where peribronchial edema narrows the airways, rather than a primary COPD or asthma exacerbation.

Evaluate the arterial blood gas results.

The ABG shows a low pH (7.26), high PaCO2 (58 mmHg), and normal HCO3 (25 mEq/L), indicating acute respiratory acidosis.

The acidosis is caused by impaired ventilation due to fluid-filled alveoli, not a primary metabolic derangement.

Select the most appropriate initial pharmacologic intervention.

Administer an intravenous loop diuretic such as furosemide.

Immediate preload reduction is required to shift fluid out of the pulmonary interstitium and improve gas exchange.

Key Concept

Differentiating acute decompensated heart failure ('cardiac asthma') from a COPD exacerbation and selecting immediate preload-reducing therapy.

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