A 68-year-old man is brought to the emergency department due to sudden-onset severe dyspne… — USMLE Step 2 CK

A 68-year-old man is brought to the emergency department due to sudden-onset severe dyspnea that awoke him from sleep. He has a history of coronary artery disease, hypertension, type 2 diabetes mellitus, and a 40-pack-year smoking history. Temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $172/96\text{ mmHg}$ , heart rate is $115/\text{min}$ , and respiratory rate is $28/\text{min}$ . Oxygen saturation is $85\%$ on room air. Physical examination reveals the use of accessory muscles of respiration. Jugular venous distention is present while sitting upright. Lung auscultation reveals bilateral expiratory wheezes and coarse crackles at the bases. Cardiac auscultation reveals a regular tachycardia with a prominent third heart sound (S3). Arterial blood gas analysis on room air shows:

pH: $7.28$
PaCO2: $58\text{ mmHg}$
PaO2: $52\text{ mmHg}$
HCO3-: $26\text{ mEq/L}$

Which of the following are the most appropriate initial management steps for this patient? (Select all that apply)

Intravenous furosemideAnswer
Initiation of noninvasive positive pressure ventilationAnswer
C
Intravenous methylprednisolone
D
Intravenous piperacillin-tazobactam
E
Intravenous sodium bicarbonate

Answer

The correct interventions are intravenous furosemide and the initiation of noninvasive positive pressure ventilation (NPPV).

The correct interventions directly address the acute volume overload and hypoxemic respiratory failure caused by acute decompensated heart failure (ADHF). Intravenous furosemide provides rapid venodilation and subsequent diuresis, reducing left ventricular preload. Noninvasive positive pressure ventilation (NPPV) provides both oxygenation support and positive intrathoracic pressure, which beneficially decreases both left ventricular preload and afterload, rapidly improving respiratory mechanics.

Step-by-Step Solution

Identify the primary clinical syndrome based on the presentation.

The patient's paroxysmal nocturnal dyspnea, jugular venous distention, S3 gallop, and bilateral crackles point strongly to acute decompensated heart failure (ADHF) with cardiogenic pulmonary edema.

Recognizing ADHF early prevents misdiagnosis as a COPD exacerbation, despite the patient's smoking history and presence of wheezing ('cardiac asthma').

Interpret the arterial blood gas values.

The ABG shows an uncompensated acute respiratory acidosis (pH

7.28

, PaCO2

58\text{ mmHg}

) and severe hypoxemia.

The expected rise in HCO3- for an acute respiratory acidosis is

1\text{ mEq/L}

for every

10\text{ mmHg}

increase in PaCO2. Since PaCO2 increased by

18\text{ mmHg}

, the HCO3- appropriately rose by approximately

1.8

26\text{ mEq/L}

, confirming no concomitant metabolic acidosis.

Select the appropriate immediate therapies for severe ADHF.

Intravenous loop diuretics (furosemide) and noninvasive positive pressure ventilation (NPPV) are selected.

These interventions rapidly decrease cardiac preload and afterload while directly addressing the severe hypoxemic and hypercapnic respiratory failure.

Key Concept

The initial management of acute decompensated heart failure with pulmonary edema involves reducing preload and afterload using intravenous diuretics, vasodilators (if normotensive or hypertensive), and noninvasive positive pressure ventilation.

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