A 62-year-old man is evaluated in the emergency department for worsening shortness of brea… — USMLE Step 2 CK

A $62$ -year-old man is evaluated in the emergency department for worsening shortness of breath, lightheadedness, and profound fatigue over the past $3$ days. He has a history of advanced non-small cell lung cancer. His temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $88/70 \text{ mm Hg}$ , pulse is $120/\text{min}$ , and respirations are $24/\text{min}$ . Pulse oximetry shows $94\%$ on room air. The patient appears dyspneic and anxious. Physical examination reveals jugular venous distention up to the angle of the mandible while sitting upright. Lungs are clear to auscultation bilaterally. Cardiac auscultation reveals distant heart sounds and tachycardia without murmurs. His systolic blood pressure drops by $15 \text{ mm Hg}$ during inspiration. Extremities are cool to the touch with faint peripheral pulses. An electrocardiogram displays sinus tachycardia with low voltage QRS complexes and beat-to-beat variation in the QRS axis. Which of the following is the most appropriate next step in the management of this patient?

Echocardiography-guided pericardiocentesisAnswer
B
Intravenous furosemide administration
C
Immediate computed tomography angiography of the chest
D
Intravenous fluid resuscitation and broad-spectrum antibiotics
E
Administration of intravenous sodium bicarbonate

Answer

Echocardiography-guided pericardiocentesis

The correct answer is echocardiography-guided pericardiocentesis. This patient has a history of lung cancer and presents with obstructive shock due to cardiac tamponade (likely secondary to a malignant pericardial effusion). The diagnosis is strongly supported by Beck's triad (hypotension, jugular venous distention, and distant heart sounds), pulsus paradoxus (a decrease in systolic blood pressure of

>10 \text{ mm Hg}

during inspiration), and electrical alternans on the electrocardiogram (caused by the heart swinging within a large fluid-filled sac). Cardiac tamponade restricts venous return and diastolic ventricular filling, leading to drastically reduced stroke volume and cardiac output. The immediate, life-saving intervention is to relieve the pressure within the pericardial sac via pericardiocentesis.

Step-by-Step Solution

Analyze the patient's vital signs and physical examination findings.

The patient has hypotension (

88/70 \text{ mm Hg}

), jugular venous distention, and distant heart sounds (Beck's triad). He also has pulsus paradoxus (systolic drop

>10 \text{ mm Hg}

during inspiration).

Identifying these classic signs points toward a specific etiology for his obstructive shock.

Evaluate the electrocardiogram findings.

The ECG shows sinus tachycardia, low voltage QRS complexes, and electrical alternans (beat-to-beat variation in QRS axis).

These findings are highly specific for a large pericardial effusion, confirming the clinical suspicion of cardiac tamponade.

Determine the most appropriate initial management for the confirmed diagnosis.

Urgent echocardiography-guided pericardiocentesis is required.

Cardiac tamponade is a life-threatening emergency caused by fluid accumulation in the pericardial space restricting ventricular filling. Immediate fluid drainage is necessary to restore stroke volume and cardiac output.

Key Concept

Cardiac tamponade presents with Beck's triad (hypotension, jugular venous distention, muffled heart sounds), pulsus paradoxus, and electrical alternans on ECG. The definitive and immediate management is urgent pericardiocentesis.

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