A 65-year-old man is evaluated in the intensive care unit for sudden-onset dyspnea and lig… — USMLE Step 2 CK

A $65$ -year-old man is evaluated in the intensive care unit for sudden-onset dyspnea and lightheadedness. The patient is currently on postoperative day $3$ following a three-vessel coronary artery bypass grafting. His recovery had been uncomplicated until $30$ minutes ago. Temperature is $37.1^\circ \text{C}$ ( $98.8^\circ \text{F}$ ), blood pressure is $82/65\text{ mm Hg}$ , pulse is $122/\text{min}$ , and respirations are $24/\text{min}$ . Physical examination reveals elevated jugular venous pressure and muffled heart sounds. The lungs are clear to auscultation bilaterally. Review of the patient's drains shows that the mediastinal chest tubes, which had been draining approximately $100\text{ mL/hr}$ of serosanguinous fluid, have drained less than $10\text{ mL}$ over the past $3$ hours. Electrocardiogram demonstrates sinus tachycardia with low-voltage QRS complexes. Which of the following is the most appropriate next step in management?

Bedside echocardiographyAnswer
B
Portable chest radiography
C
Intravenous fluid bolus and serial observation
D
Administration of intravenous furosemide
E
Empiric administration of broad-spectrum antibiotics

Answer

The correct answer is bedside echocardiography.

The correct answer is bedside echocardiography. This patient is experiencing postoperative cardiac tamponade, a critical complication of cardiothoracic surgery. The classic presentation includes Beck's triad: hypotension with a narrowed pulse pressure, jugular venous distention, and muffled heart sounds. In the postoperative cardiac setting, this is frequently precipitated by the occlusion of mediastinal chest tubes by a thrombus. The abrupt cessation of drainage causes ongoing bleeding to accumulate rapidly within the confined pericardial space. This increases intrapericardial pressure, restricts ventricular filling (diastole), and results in obstructive shock. Bedside echocardiography is the most appropriate next step because it rapidly and non-invasively confirms the diagnosis by visualizing the pericardial effusion and right ventricular diastolic collapse, paving the way for definitive emergency surgical re-exploration (resternotomy).

Step-by-Step Solution

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

The patient exhibits hypotension with a narrow pulse pressure (

82/65\text{ mm Hg}

), tachycardia, elevated jugular venous pressure, and muffled heart sounds.

These findings represent Beck's triad, which is highly indicative of cardiac tamponade resulting in obstructive shock.

Correlate the physical findings with the postoperative context and surgical drain output.

The patient is on postoperative day

3

from a CABG and had an abrupt cessation of mediastinal chest tube drainage (from

100\text{ mL/hr}

<10\text{ mL}

over

3

hours).

Sudden cessation of drainage often indicates chest tube occlusion by a blood clot, leading to rapid accumulation of blood in the pericardial space.

Identify the most appropriate next step in management based on the suspected diagnosis.

Bedside echocardiography is required to confirm the diagnosis.

Echocardiography is a rapid, non-invasive tool that definitively identifies pericardial fluid and right ventricular diastolic collapse before proceeding to emergency resternotomy.

Key Concept

Cardiac tamponade is a life-threatening complication of cardiothoracic surgery that classically presents with Beck's triad and sudden cessation of chest tube drainage; it requires immediate bedside echocardiography for confirmation followed by surgical re-exploration.

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