A 70-year-old man comes to the emergency department at 2:00 AM due to acute-onset, severe … — USMLE Step 2 CK

A $70$ -year-old man comes to the emergency department at $2:00$ AM due to acute-onset, severe shortness of breath that awoke him from sleep. He has a history of severe chronic obstructive pulmonary disease (COPD) and coronary artery disease. He reports a dry cough but denies fever, chills, or increased sputum production. His current medications include an umeclidinium-vilanterol inhaler, aspirin, and atorvastatin. His temperature is $37.1^\circ$ C ( $98.8^\circ$ F), blood pressure is $165/95$ mm Hg, pulse is $115$ /min, and respirations are $28$ /min. Pulse oximetry shows $85\%$ on room air. The patient is diaphoretic, speaks in short sentences, and is using accessory muscles of respiration. Jugular venous pressure is $10$ cm $H_2O$ . Pulmonary examination reveals a prolonged expiratory phase with diffuse bilateral wheezing. Cardiac examination shows tachycardia with a regular rhythm and an $S_3$ gallop.

Arterial blood gas analysis on room air reveals:

pH: $7.25$
$PaCO_2$ : $60$ mm Hg
$PaO_2$ : $52$ mm Hg
$HCO_3^-$ : $26$ mEq/L

Chest radiography reveals prominent pulmonary vasculature, Kerley B lines, and a slightly enlarged cardiac silhouette.

Which of the following is the most appropriate next step in management?

A
Inhaled albuterol-ipratropium, systemic corticosteroids, and oral azithromycin
B
Intravenous piperacillin-tazobactam and vancomycin
C
Intravenous sodium bicarbonate infusion
Intravenous furosemide and noninvasive positive-pressure ventilationAnswer
E
Endotracheal intubation and mechanical ventilation

Answer

Intravenous furosemide and noninvasive positive-pressure ventilation

The correct answer is intravenous furosemide and noninvasive positive-pressure ventilation (NPPV). This patient presents with acute decompensated heart failure (ADHF) presenting as 'cardiac asthma.' While his history of COPD and presentation with wheezing may initially suggest a COPD exacerbation, several key findings point definitively to ADHF: the acute onset of paroxysmal nocturnal dyspnea, elevated jugular venous pressure, an

S_3

gallop, and chest radiography showing Kerley B lines and cardiomegaly. The wheezing is caused by peribronchial edema leading to bronchospasm. Initial management of ADHF with acute pulmonary edema and respiratory failure includes loop diuretics (e.g., intravenous furosemide) to reduce fluid overload. Additionally, because the patient has severe respiratory distress and acute respiratory acidosis (

pH

7.25

PaCO_2

60

mm Hg), NPPV is indicated. NPPV improves oxygenation, decreases the work of breathing, and provides positive intrathoracic pressure, which favorably reduces both left ventricular preload and afterload.

Step-by-Step Solution

Analyze the patient's presentation and history.

The patient has a history of COPD but presents with paroxysmal nocturnal dyspnea, elevated JVP, an S3 gallop, and Kerley B lines on chest radiography.

To differentiate between COPD exacerbation and acute decompensated heart failure as the primary cause of acute respiratory failure.

Interpret the arterial blood gas values.

The ABG shows a pH of 7.25, PaCO2 of 60 mm Hg, and HCO3- of 26 mEq/L, indicating a pure acute respiratory acidosis.

To determine the severity of respiratory failure and rule out a mixed acid-base disorder that might change management.

Select the most appropriate initial management based on the diagnosis.

Intravenous loop diuretics and noninvasive positive-pressure ventilation (NPPV).

Diuresis treats the underlying volume overload of ADHF, while NPPV provides immediate respiratory support, decreasing work of breathing and improving cardiac hemodynamics.

Key Concept

Patients with acute decompensated heart failure can present with wheezing ('cardiac asthma') mimicking a COPD exacerbation. Key distinguishing features include an S3 gallop, elevated JVP, and radiographic evidence of pulmonary edema. First-line management includes loop diuretics and noninvasive positive-pressure ventilation.

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