An 82-year-old woman is brought to the emergency department at 3:00 AM by her daughter due… — USMLE Step 2 CK

An 82-year-old woman is brought to the emergency department at 3:00 AM by her daughter due to sudden, severe difficulty breathing. The patient reports waking up feeling as if she were smothering and has been coughing up pink, frothy sputum. Her medical history includes long-standing hypertension, diet-controlled type 2 diabetes mellitus, and a 45-pack-year smoking history, though she quit 5 years ago. Her temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $185/105\text{ mm Hg}$ , pulse is $112/\text{min}$ , and respiratory rate is $28/\text{min}$ . Pulse oximetry shows an oxygen saturation of $85\%$ on room air. The patient is sitting upright and using accessory muscles of respiration. Examination of the neck reveals jugular venous distention $10\text{ cm}$ above the sternal angle. Pulmonary auscultation reveals widespread, high-pitched expiratory wheezes and scattered fine crackles in the bilateral lower lung zones. Cardiac auscultation reveals a regular rhythm, tachycardia, and a prominent S3 gallop. Bilateral $2+$ pitting edema is noted up to the mid-calves. Arterial blood gas analysis on room air shows:

$\text{pH}: 7.28$
$\text{PaCO}_2: 56\text{ mm Hg}$
$\text{PaO}_2: 52\text{ mm Hg}$
$\text{HCO}_3^-: 25\text{ mEq/L}$

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

Intravenous furosemideAnswer
B
Intravenous methylprednisolone and nebulized ipratropium-albuterol
C
Oral azithromycin and intravenous ceftriaxone
D
Intravenous sodium bicarbonate
E
Intravenous metoprolol tartrate

Answer

Intravenous furosemide

The most appropriate initial pharmacologic therapy for this patient is an intravenous loop diuretic, such as furosemide. This patient's presentation of severe dyspnea, orthopnea, pink frothy sputum, jugular venous distention, an S3 gallop, and bilateral edema is highly characteristic of acute decompensated heart failure (ADHF) with cardiogenic pulmonary edema. In ADHF, increased left ventricular end-diastolic pressure leads to elevated pulmonary capillary hydrostatic pressure and subsequent fluid transudation into the alveoli and peribronchial interstitium. This peribronchial edema causes airway narrowing, frequently manifesting as wheezing (so-called 'cardiac asthma'). Intravenous loop diuretics rapidly reduce intravascular volume and provide immediate venodilation, which decreases venous return (preload) and relieves the pulmonary congestion. Noninvasive positive-pressure ventilation (NIPPV) is also indicated given her respiratory acidosis, but among the pharmacologic choices, furosemide is the necessary first step.

Step-by-Step Solution

Analyze the patient's clinical presentation and vital signs.

The patient has acute-onset dyspnea, orthopnea/paroxysmal nocturnal dyspnea, severe hypertension, hypoxia, and pink frothy sputum.

Identifying the onset and character of the respiratory distress helps differentiate between pulmonary, cardiac, and infectious etiologies.

Evaluate the physical examination findings.

Findings include jugular venous distention, an S3 gallop, bilateral lower extremity edema, and wheezing with fine crackles.

An S3 gallop and elevated right-sided pressures (JVD, edema) in the setting of acute respiratory distress strongly indicate acute left ventricular failure with secondary pulmonary edema, rather than primary lung disease.

Interpret the arterial blood gas (ABG) results.

The ABG shows a low pH (7.28), elevated PaCO2 (56 mm Hg), and normal HCO3- (25 mEq/L), indicating acute, uncompensated respiratory acidosis.

The respiratory acidosis is secondary to alveolar flooding (pulmonary edema) causing a severe ventilation-perfusion mismatch and fatigue of respiratory muscles.

Determine the most appropriate initial intervention.

The correct treatment is preload reduction with an intravenous loop diuretic (furosemide), often combined with vasodilators (like nitroglycerin) and noninvasive positive-pressure ventilation.

Reducing pulmonary capillary hydrostatic pressure directly targets the underlying pathophysiology of acute pulmonary edema.

Key Concept

Acute decompensated heart failure (ADHF) can present with prominent wheezing ('cardiac asthma') due to peribronchial edema, which must be differentiated from COPD exacerbation using clinical signs like an S3 gallop, JVD, and orthopnea.

Estimated Time:1m 30s

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