A 68-year-old man arrives at the emergency department reporting two days of progressively … — USMLE Step 2 CK

A 68-year-old man arrives at the emergency department reporting two days of progressively worsening dyspnea and an inability to lie flat without severe respiratory distress. He has a past medical history of chronic obstructive pulmonary disease (COPD), diet-controlled type 2 diabetes mellitus, and hypertension. Current medications include inhaled tiotropium and oral amlodipine. His temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $174/96\ \text{mm Hg}$ , pulse is $116/\text{min}$ , and respiratory rate is $28/\text{min}$ . Pulse oximetry indicates an oxygen saturation of $87\%$ on room air. Physical examination reveals a patient in moderate respiratory distress using accessory muscles. Jugular venous pressure is elevated to $11\ \text{cm H}_2\text{O}$ above the sternal angle. Pulmonary auscultation reveals a prolonged expiratory phase with diffuse bilateral wheezing and scattered crackles at the lung bases. Cardiac examination shows tachycardia with a regular rhythm and an audible S3 gallop. There is $2+$ pitting edema in the lower extremities bilaterally.

Laboratory results are as follows:
Leukocyte count: $8,200/\text{mm}^3$
Thyroid-stimulating hormone (TSH): $0.2\ \mu\text{IU}/\text{mL}$ (Normal: $0.4\text{-}4.0$ )
Free T4: $1.2\ \text{ng}/\text{dL}$ (Normal: $0.9\text{-}1.7$ )
N-terminal pro-B-type natriuretic peptide (NT-proBNP): $2,800\ \text{pg}/\text{mL}$

Arterial blood gas analysis on room air reveals:
pH: $7.25$
$\text{PaCO}_2$ : $64\ \text{mm Hg}$
$\text{PaO}_2$ : $55\ \text{mm Hg}$
$\text{HCO}_3^-$ : $27\ \text{mEq}/\text{L}$

A portable chest radiograph displays cardiomegaly, bilateral pleural effusions, prominent upper lobe pulmonary vessels, and hyperinflated lung fields. Which of the following is the most appropriate next step in the management of this patient?

Administration of intravenous furosemide and noninvasive positive pressure ventilationAnswer
B
Administration of systemic glucocorticoids and scheduled nebulized ipratropium-albuterol
C
Infusion of intravenous sodium bicarbonate for an uncompensated metabolic acidosis
D
Initiation of empiric intravenous vancomycin and piperacillin-tazobactam
E
Initiation of methimazole to treat high-output cardiac failure

Answer

The most appropriate next step is the administration of intravenous furosemide and noninvasive positive pressure ventilation.

The correct answer addresses the patient's underlying acute decompensated heart failure (ADHF). The patient presents with classic signs of left and right heart failure, including an S3 gallop, elevated jugular venous pressure, peripheral edema, and a markedly elevated NT-proBNP. The diffuse wheezing on auscultation represents 'cardiac asthma,' which is caused by peribronchial edema narrowing the airways. The chest radiograph confirms cardiomegaly and pulmonary venous congestion (cephalization, effusions). In patients with ADHF complicated by severe respiratory distress and respiratory acidosis (as seen on the ABG), the immediate management involves noninvasive positive pressure ventilation (NPPV) to reduce the work of breathing and decrease left ventricular preload and afterload, along with intravenous loop diuretics (furosemide) for rapid volume reduction.

Step-by-Step Solution

Analyze the clinical presentation to differentiate the cause of respiratory distress.

The patient has a history of COPD and presents with wheezing, but also has an elevated jugular venous pressure, an S3 gallop, peripheral edema, and an elevated NT-proBNP.

These findings are highly specific for volume overload and acute decompensated heart failure, identifying the wheezing as 'cardiac asthma' rather than a primary COPD exacerbation.

Interpret the arterial blood gas (ABG) findings.

The ABG shows a low pH (

7.25

) and a highly elevated

\text{PaCO}_2

(

64\ \text{mm Hg}

) with a slightly elevated

\text{HCO}_3^-

(

27\ \text{mEq}/\text{L}

This indicates an acute-on-chronic respiratory acidosis resulting from alveolar hypoventilation secondary to severe pulmonary edema, not a primary metabolic derangement.

Interpret the thyroid function tests.

The patient has a low TSH but a normal free T4.

This pattern in an acutely ill patient points to euthyroid sick syndrome, ruling out primary hyperthyroidism as a cause for a high-output state.

Determine the optimal acute management for acute decompensated heart failure with respiratory acidosis.

Select noninvasive positive pressure ventilation (NPPV) and intravenous loop diuretics (e.g., furosemide).

NPPV rapidly decreases the work of breathing, improves oxygenation, and reduces left ventricular preload and afterload. Furosemide provides necessary diuresis and venodilation to relieve volume overload.

Key Concept

Patients with acute decompensated heart failure can present with prominent wheezing ('cardiac asthma') mimicking a COPD exacerbation; differentiation relies on signs of volume overload (elevated JVP, S3 gallop), biomarkers (BNP), and radiographic evidence of pulmonary venous congestion.

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