A 72-year-old woman is brought to the emergency department via ambulance due to a two-day … — USMLE Step 2 CK

A $72$ -year-old woman is brought to the emergency department via ambulance due to a two-day history of worsening shortness of breath and orthopnea. She reports waking up gasping for air last night. She has a medical history of chronic obstructive pulmonary disease (COPD), diet-controlled type 2 diabetes mellitus, and a known pituitary microadenoma. Her home medications include a long-acting muscarinic antagonist and levothyroxine.

On triage, her temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $162/92$ mm Hg, pulse is $115$ /min, and respiratory rate is $28$ /min. Pulse oximetry shows an oxygen saturation of $85\%$ on room air. Physical examination reveals prominent jugular venous distention. Lung auscultation demonstrates diffuse fine crackles bilaterally with scattered expiratory wheezes. Cardiac examination reveals a regular tachycardia with a distinct $S_3$ gallop. The lower extremities have $2+$ pitting edema to the knees.

Laboratory results are as follows:

Test	Result
Sodium	$139$ mEq/L
Potassium	$4.2$ mEq/L
Chloride	$96$ mEq/L
Bicarbonate	$34$ mEq/L
Blood urea nitrogen	$32$ mg/dL
Creatinine	$1.4$ mg/dL
Thyroid-stimulating hormone (TSH)	$0.15$ $\mu$ U/mL (Normal: $0.5$ - $5.0$ $\mu$ U/mL)
Free thyroxine (T4)	$0.6$ ng/dL (Normal: $0.9$ - $1.7$ ng/dL)

Arterial blood gas on room air:

Test	Result
pH	$7.24$
PaCO2	$74$ mm Hg
PaO2	$52$ mm Hg

A portable chest radiograph displays an enlarged cardiac silhouette, prominent perihilar opacities, and bilateral blunting of the costophrenic angles. There is no lobar consolidation. The patient is placed on noninvasive positive pressure ventilation.

Which of the following is the most appropriate pharmacological intervention for this patient's acute presentation?

Intravenous loop diuretic administrationAnswer
B
Administration of systemic methylprednisolone
C
Broad-spectrum coverage with vancomycin and cefepime
D
Intravenous infusion of sodium bicarbonate
E
Upward titration of current levothyroxine dosage

Answer

Intravenous loop diuretic administration

The patient's clinical presentation is classic for acute decompensated heart failure (ADHF), characterized by volume overload (jugular venous distention, peripheral edema) and pulmonary edema (orthopnea, paroxysmal nocturnal dyspnea, crackles, and an S3 gallop). The chest radiograph confirms cardiomegaly and perihilar opacities. The expiratory wheezes represent 'cardiac asthma' due to peribronchial edema rather than a primary obstructive airway exacerbation. For patients presenting with ADHF and pulmonary edema, rapid preload reduction is essential. The most appropriate initial pharmacological therapy, in conjunction with noninvasive positive pressure ventilation, is an intravenous loop diuretic. This effectively promotes diuresis, decreases intravascular volume, and relieves pulmonary congestion.

Step-by-Step Solution

Synthesize the clinical and radiographic findings to identify the primary cause of acute respiratory failure.

The presence of orthopnea, an S3 gallop, jugular venous distention, and perihilar opacities confirms acute decompensated heart failure (ADHF) with pulmonary edema, despite the history of COPD and the presence of wheezing (cardiac asthma).

Accurate differentiation between ADHF and a COPD exacerbation dictates the immediate life-saving treatment pathway.

Interpret the arterial blood gas values in the context of the patient's underlying conditions.

The low pH, significantly elevated PaCO2, and elevated baseline bicarbonate indicate an acute-on-chronic respiratory acidosis secondary to pulmonary edema superimposed on chronic COPD.

Correct acid-base interpretation prevents the inappropriate administration of buffering agents like sodium bicarbonate, which can worsen respiratory acidosis.

Analyze the thyroid panel to determine its relevance to the acute presentation.

The low free T4 and low-normal TSH suggest central hypothyroidism related to the patient's pituitary microadenoma.

Recognizing this pattern prevents the misdiagnosis of primary hypothyroidism and avoids inappropriate dose adjustments during an acute cardiopulmonary crisis.

Select the most appropriate acute pharmacological management.

Administration of an intravenous loop diuretic is the correct next step to provide rapid diuresis and preload reduction.

Preload reduction is the cornerstone of therapy to relieve pulmonary congestion in patients presenting with ADHF.

Key Concept

Management of acute decompensated heart failure presenting with mixed cardiopulmonary symptoms.

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