A 71-year-old man is transported to the emergency department from a local nursing facility… — USMLE Step 2 CK

A 71-year-old man is transported to the emergency department from a local nursing facility due to the sudden onset of severe breathlessness and orthopnea that started 3 hours ago. He has a past medical history of severe chronic obstructive pulmonary disease (COPD) and ischemic cardiomyopathy with a left ventricular ejection fraction of $30\%$ .

Upon arrival, he is visibly agitated and using accessory muscles of respiration. Vital signs are:
- Temperature: $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ )
- Blood pressure: $172/100\text{ mm Hg}$
- Heart rate: $118\text{/min}$ and regular
- Respiratory rate: $29\text{/min}$
- Oxygen saturation: $82\%$ on ambient air

Physical examination reveals jugular venous distention when sitting upright at 45 degrees. Chest auscultation demonstrates widespread expiratory wheezing mixed with fine bibasilar crackles. Cardiac auscultation reveals tachycardia and a prominent third heart sound (S3). There is 2+ bilateral pitting edema up to the knees.

Arterial blood gas analysis on ambient air shows:
- pH: 7.22
- $PaCO_2$ : $75\text{ mm Hg}$
- $PaO_2$ : $48\text{ mm Hg}$
- $HCO_3^-$ : $31\text{ mEq/L}$

Which of the following are the most appropriate initial steps in the management of this patient? (Select exactly two)

Apply noninvasive positive-pressure ventilationAnswer
Administer a rapid-acting intravenous loop diureticAnswer
C
Commence empiric broad-spectrum antibiotics and systemic corticosteroids
D
Infuse intravenous sodium bicarbonate to correct the acidemia
E
Administer high-dose nebulized bronchodilators as the primary therapy

Answer

The most appropriate initial steps are applying noninvasive positive-pressure ventilation (NPPV) and administering a rapid-acting intravenous loop diuretic.

The correct interventions directly address the pathophysiology of acute decompensated heart failure (ADHF). Noninvasive positive-pressure ventilation (NPPV) provides positive intrathoracic pressure, which decreases venous return (preload) and reduces left ventricular transmural pressure (afterload), thereby improving cardiac output. It also recruits fluid-filled alveoli, improving gas exchange and reducing the work of breathing. Intravenous loop diuretics (e.g., furosemide) are indicated to rapidly reduce intravascular volume and alleviate venous congestion.

Step-by-Step Solution

Analyze the clinical presentation and physical examination findings.

The patient presents with severe respiratory distress, hypertension, JVD, an S3 gallop, bibasilar crackles, and peripheral edema.

These are classic signs of acute decompensated heart failure (ADHF) with volume overload. The wheezing represents 'cardiac asthma' secondary to peribronchial edema, not necessarily a primary COPD exacerbation.

Interpret the arterial blood gas (ABG) results.

The ABG shows acidemia (pH 7.22), severe hypercapnia (

PaCO_2

75\text{ mm Hg}

), hypoxemia (

PaO_2

48\text{ mm Hg}

), and an elevated bicarbonate (

HCO_3^-

31\text{ mEq/L}

This indicates an acute-on-chronic respiratory acidosis. The elevated bicarbonate reflects baseline chronic

CO_2

retention from severe COPD, while the acute drop in pH is driven by the sudden rise in

PaCO_2

due to alveolar flooding from cardiogenic pulmonary edema.

Determine the optimal immediate interventions based on the diagnosis.

The patient requires immediate support for oxygenation and ventilation, along with aggressive volume removal.

NPPV effectively supports ventilation, reduces the work of breathing, and provides favorable hemodynamic effects (decreased preload and afterload). Intravenous loop diuretics are required to rapidly treat the volume overload.

Key Concept

The initial management of acute decompensated heart failure (ADHF) complicated by acute hypercapnic respiratory failure prioritizes noninvasive positive-pressure ventilation (NPPV) and intravenous loop diuretics, while differentiating 'cardiac asthma' from a primary COPD exacerbation.

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