Emergency medical services bring an 81-year-old woman to the hospital after she awoke gasp… — USMLE Step 2 CK

Emergency medical services bring an $81$ -year-old woman to the hospital after she awoke gasping for air. Her daughter reports that the patient has been sleeping in a recliner for the past week due to a persistent nighttime cough and an inability to lie flat. Past medical history includes long-standing hypertension, diet-controlled type 2 diabetes mellitus, and a $40$ -pack-year smoking history, though she quit a decade ago. A recent outpatient laboratory report from two days ago shows a thyroid-stimulating hormone (TSH) level of $1.2\ \mu\text{U/mL}$ (normal: $0.4\text{-}4.0\ \mu\text{U/mL}$ ) and a free thyroxine (T4) level of $0.5\ \text{ng/dL}$ (normal: $0.9\text{-}1.7\ \text{ng/dL}$ ). Upon arrival, the patient is visibly anxious, using accessory muscles of respiration, and unable to speak in full sentences. Vital signs show a temperature of $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure of $182/105\ \text{mm Hg}$ , pulse of $115\ \text{beats/min}$ , and respirations of $28\ \text{breaths/min}$ . Pulse oximetry reveals an oxygen saturation of $86\%$ on ambient air. Physical examination demonstrates distended jugular veins when sitting upright. Auscultation of the chest reveals diffuse bilateral crackles extending to the apices, accompanied by scattered expiratory wheezes. Cardiac auscultation reveals a regular tachycardia with a prominent extra heart sound occurring just after $S_2$ . The lower extremities show $2+$ bilateral pitting edema to the knees. Arterial blood gas analysis on room air demonstrates a pH of $7.48$ , a $p\text{CO}_2$ of $31\ \text{mm Hg}$ , and a $p\text{O}_2$ of $54\ \text{mm Hg}$ . Which of the following is the most appropriate initial step in the management of this patient?

A
Administration of inhaled bronchodilators and systemic glucocorticoids
B
Application of Winter's formula to determine expected carbon dioxide levels
Noninvasive positive-pressure ventilation and intravenous furosemideAnswer
D
Administration of levothyroxine for primary hypothyroidism
E
Titration of supplemental oxygen to a target saturation of $88\%$ to $92\%$

Answer

The most appropriate initial management is noninvasive positive-pressure ventilation (NIPPV) and intravenous furosemide.

The correct intervention addresses both the critical hypoxia and the underlying volume overload of acute decompensated heart failure (ADHF). Noninvasive positive-pressure ventilation (NIPPV) provides immediate alveolar recruitment, decreases the work of breathing, and reduces left ventricular preload and afterload. Concurrently, intravenous loop diuretics (e.g., furosemide) promote rapid diuresis and venodilation, resolving the pulmonary edema.

Step-by-Step Solution

Identify the primary clinical syndrome based on history and physical exam findings.

The patient has acute decompensated heart failure (ADHF) with severe pulmonary edema and 'cardiac asthma'.

Orthopnea, paroxysmal nocturnal dyspnea, extreme hypertension, jugular venous distention, crackles, and an

S_3

gallop strongly point to left-sided heart failure rather than primary pulmonary disease.

Determine the most urgent therapeutic priority.

Immediate respiratory and hemodynamic support via oxygenation and volume reduction.

The patient is severely hypoxic (

86\%

on room air) and in respiratory distress. NIPPV rapidly improves oxygenation and decreases the work of breathing, while intravenous loop diuretics (like furosemide) clear pulmonary congestion.

Evaluate the diagnostic distractors provided in the vignette.

Exclude COPD exacerbation and acute interventions for endocrine or acid-base anomalies.

The low free T4 with a normal TSH indicates secondary (not primary) hypothyroidism, which is non-contributory here. The ABG reveals respiratory alkalosis, making Winter's formula (used for metabolic acidosis) irrelevant. The wheezing is due to peribronchial edema, not primary bronchospasm.

Key Concept

The classic presentation of acute decompensated heart failure (ADHF) includes orthopnea, JVD, an S3 gallop, and pulmonary edema, which requires urgent treatment with noninvasive positive-pressure ventilation and intravenous loop diuretics. It must be carefully distinguished from COPD exacerbation, which may present similarly with wheezing.

Alternative Method

In the setting of severe hypertensive acute decompensated heart failure (as seen with this patient's BP of 182/105 mm Hg), intravenous vasodilators such as nitroglycerin or nitroprusside are also highly effective adjuncts to rapidly reduce afterload, provided the patient has adequate blood pressure.

Estimated Time:1m 30s

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