Paramedics transport a 74-year-old female to the emergency department because she awoke su… — USMLE Step 2 CK

Paramedics transport a 74-year-old female to the emergency department because she awoke suddenly with a sensation of suffocating. Her medical history is notable for hypertension, diet-controlled type 2 diabetes mellitus, and a 40-pack-year smoking history. Current medications include daily amlodipine and metoprolol succinate. Upon arrival, she appears in acute distress, sitting upright and using accessory muscles of respiration. Vital signs are temperature $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure $182/105\text{ mm Hg}$ , pulse $114/\text{min}$ , and respirations $28/\text{min}$ . Pulse oximetry is $88\%$ on room air.

Physical examination reveals marked jugular venous distention to $11\text{ cm H}_2\text{O}$ . Lung auscultation demonstrates diffuse expiratory wheezing and coarse crackles extending halfway up both posterior lung fields. Cardiac auscultation is limited by breath sounds but reveals a regular tachycardia and a low-frequency diastolic sound heard best at the cardiac apex.

Arterial blood gas analysis on room air reveals the following:

Parameter	Value	Reference Range
pH	$7.28$	$7.35 - 7.45$
PaCO $_2$	$56\text{ mm Hg}$	$35 - 45\text{ mm Hg}$
PaO $_2$	$58\text{ mm Hg}$	$75 - 105\text{ mm Hg}$
HCO $_3^-$	$25\text{ mEq/L}$	$22 - 28\text{ mEq/L}$

Chest radiography displays an enlarged cardiac silhouette, prominent interstitial markings, and bilateral pleural effusions.

What is the most appropriate initial pharmacologic therapy for this patient?

Intravenous bumetanideAnswer
B
Systemic methylprednisolone and inhaled ipratropium
C
Intravenous piperacillin-tazobactam
D
Intravenous sodium bicarbonate
E
Continuous nebulized albuterol

Answer

Intravenous bumetanide

Intravenous loop diuretics, such as bumetanide, are the first-line pharmacologic therapy for acute decompensated heart failure (ADHF). They rapidly reduce intravascular volume and venous return (preload), which decreases pulmonary capillary hydrostatic pressure and relieves pulmonary edema. This patient's presentation of sudden-onset paroxysmal nocturnal dyspnea, elevated jugular venous pressure, an S3 gallop, and radiographic evidence of cardiomegaly strongly points to left ventricular failure. The prominent wheezing is a classic presentation of 'cardiac asthma,' caused by peribronchial fluid accumulation, which must be treated with diuresis.

Step-by-Step Solution

Analyze the patient's history and vital signs.

The patient is a 74-year-old with cardiovascular risk factors presenting with acute respiratory distress, severe hypertension, tachycardia, and hypoxia.

Establishing baseline stability and risk factors helps narrow the differential diagnosis for acute dyspnea.

Interpret the physical examination findings.

Elevated jugular venous pressure, an S3 gallop (low-frequency diastolic sound), and bilateral crackles are present.

These findings are highly specific for left ventricular volume overload and elevated filling pressures, pointing toward a cardiac etiology despite the wheezing.

Evaluate the objective diagnostic data.

The chest radiograph confirms cardiogenic pulmonary edema. The arterial blood gas demonstrates acute respiratory acidosis (low pH, high PaCO2) with normal bicarbonate, indicating acute hypoventilation due to alveolar fluid.

Objective data differentiates cardiogenic pulmonary edema from primary pulmonary pathologies like COPD exacerbation or severe pneumonia.

Determine the most appropriate initial intervention.

Intravenous loop diuretics (such as bumetanide or furosemide) are indicated.

Rapid reduction of preload is required to relieve the pulmonary congestion driving the patient's acute respiratory failure.

Key Concept

Patients with acute decompensated heart failure can present with wheezing ('cardiac asthma') due to peribronchial edema; management centers on preload reduction with intravenous loop diuretics rather than bronchodilators.

Estimated Time:1m 30s

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