A 61-year-old man is brought to the emergency department due to a three-day history of pro… — USMLE Step 2 CK

A 61-year-old man is brought to the emergency department due to a three-day history of progressively worsening breathlessness, orthopnea, and a cough productive of clear sputum. His past medical history is significant for severe chronic obstructive pulmonary disease (COPD), ischemic cardiomyopathy with a left ventricular ejection fraction of $35\%$ , and diet-controlled type 2 diabetes mellitus. Vital signs show a temperature of $37.1^\circ$ C ( $98.8^\circ$ F), pulse of 112/min, blood pressure of 155/92 mm Hg, and respiratory rate of 26/min. Pulse oximetry demonstrates an oxygen saturation of $86\%$ on room air. Physical examination reveals neck veins distended to 11 cm $H_2O$ while the patient is seated at a 45-degree angle. Auscultation of the lungs demonstrates prominent bibasilar crackles without any wheezing. Cardiac examination reveals a regular tachycardia and an $S_3$ gallop. The lower extremities exhibit $2+$ pitting edema bilaterally.

Laboratory results are as follows:

Test	Result
Leukocyte count	$8,200/\text{mm}^3$
Serum sodium	136 mEq/L
Serum potassium	4.1 mEq/L
Serum chloride	99 mEq/L
Serum bicarbonate	29 mEq/L
Blood urea nitrogen	32 mg/dL
Serum creatinine	1.4 mg/dL
TSH	0.2 mU/L (Normal: 0.5-5.0)
Free $T_4$	0.7 ng/dL (Normal: 0.9-1.7)

An arterial blood gas on room air shows a pH of 7.26, a $PaCO_2$ of 65 mm Hg, and a $PaO_2$ of 52 mm Hg.

Which of the following is the most appropriate initial pharmacological step in the management of this patient?

A
Prescribe systemic methylprednisolone and nebulized albuterol
Administer intravenous furosemideAnswer
C
Initiate empiric therapy with cefepime and azithromycin
D
Begin levothyroxine replacement therapy
E
Infuse acetazolamide to accelerate renal bicarbonate excretion

Answer

The most appropriate initial pharmacological step is to administer intravenous furosemide to aggressively manage the acute decompensated heart failure.

This patient presents with classic signs of acute decompensated heart failure (ADHF), including orthopnea, elevated jugular venous pressure (11 cm

H_2O

), an

S_3

gallop, bibasilar crackles without wheezing, and peripheral edema. Despite his history of COPD, the specific clinical signs (particularly the

S_3

gallop and lack of wheezing) indicate that cardiogenic pulmonary edema is the primary cause of his acute respiratory failure. The cornerstone of initial pharmacological management for volume overload in ADHF is intravenous loop diuretics, such as furosemide, which rapidly reduce preload, decrease pulmonary capillary wedge pressure, and relieve pulmonary congestion.

Step-by-Step Solution

Analyze the physical examination findings.

The patient has an elevated jugular venous pressure, bibasilar crackles without wheezing, an

S_3

gallop, and pitting edema.

These findings strongly differentiate acute decompensated heart failure (cardiogenic pulmonary edema) from a COPD exacerbation.

Evaluate the arterial blood gas and basic metabolic panel.

The ABG reveals a primary respiratory acidosis (pH 7.26,

PaCO_2

65 mm Hg) with a partially elevated bicarbonate (29 mEq/L).

This indicates an acute-on-chronic respiratory acidosis typical for a patient with baseline COPD who is acutely hypoventilating due to severe pulmonary edema.

Assess the thyroid function tests.

TSH and Free

T_4

are both low in the setting of severe acute illness.

This pattern is characteristic of euthyroid sick syndrome (non-thyroidal illness syndrome), which requires observation rather than hormone replacement.

Determine the optimal therapeutic intervention.

Administer intravenous loop diuretics (e.g., furosemide).

Rapid preload reduction is required to alleviate pulmonary congestion and improve oxygenation in acute decompensated heart failure.

Key Concept

Differentiating acute decompensated heart failure from COPD exacerbations clinically, while recognizing euthyroid sick syndrome and appropriate acid-base compensation patterns in acutely ill patients.

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