An urgent bedside evaluation is requested for a 71-year-old man in the intensive care unit… — USMLE Step 2 CK

An urgent bedside evaluation is requested for a $71$ -year-old man in the intensive care unit who developed abrupt, severe shortness of breath and altered mental status. He was admitted $5$ days ago after sustaining a comminuted left femoral shaft fracture in a motor vehicle collision, for which he underwent open reduction and internal fixation. Today, he became suddenly agitated and then poorly responsive.

Vital signs are:

Parameter	Value
Temperature	$37.9^\circ\text{C}$ ( $100.2^\circ\text{F}$ )
Blood pressure	$62/40\text{ mm Hg}$
Heart rate	$134/\text{min}$
Respiratory rate	$36/\text{min}$
SpO $_2$	$81\%$ on $15\text{ L/min}$ nonrebreather mask

Physical examination shows profound diaphoresis and mottling of the lower extremities. The jugular venous pulsation is visible at the angle of the mandible while sitting at $45^\circ$ . Auscultation of the lungs reveals clear breath sounds bilaterally. Cardiac examination shows a tachycardic, regular rhythm with a prominent parasternal heave and a right-sided S3 gallop.

An arterial blood gas analysis reveals:

Parameter	Value
pH	$7.32$
PaCO $_2$	$32\text{ mm Hg}$
PaO $_2$	$56\text{ mm Hg}$
HCO $_3^-$	$16\text{ mEq/L}$

A 12-lead ECG demonstrates sinus tachycardia with new T-wave inversions in leads V1-V4 and a complete right bundle branch block.

Which of the following is the most appropriate next step in management?

A
Computed tomography pulmonary angiography
Bedside transthoracic echocardiographyAnswer
C
Intravenous furosemide
D
Intravenous sodium bicarbonate
E
Intravenous piperacillin-tazobactam

Answer

Bedside transthoracic echocardiography

The correct answer is bedside transthoracic echocardiography. This patient is presenting with classic signs of a massive pulmonary embolism (PE) leading to acute right ventricular failure and obstructive shock. Risk factors include recent major orthopedic surgery and immobilization. In a hemodynamically unstable patient (systolic blood pressure < 90 mm Hg) with suspected massive PE, transporting the patient out of the intensive care unit for definitive imaging (CT pulmonary angiography) is contraindicated due to the high risk of cardiovascular collapse. The standard of care is to perform bedside transthoracic echocardiography to look for signs of right ventricular dysfunction (e.g., RV dilation, McConnell's sign). If RV strain is confirmed, the patient should proceed to reperfusion therapy (e.g., catheter-directed thrombolysis or surgical embolectomy, as systemic thrombolytics are contraindicated so soon after major surgery).

Step-by-Step Solution

Analyze the clinical presentation and hemodynamics.

The patient has severe hypotension, jugular venous distention, clear lungs, and ECG signs of right heart strain (RBBB, anterior T-wave inversions).

This triad strongly suggests obstructive shock due to acute right ventricular failure, highly suspicious for a massive pulmonary embolism (PE) given the recent major orthopedic surgery.

Evaluate the stability of the patient for diagnostic testing.

With a blood pressure of 62/40 mm Hg and profound hypoxia, the patient is hemodynamically unstable.

Unstable patients cannot safely leave the ICU for advanced imaging due to the high risk of decompensation and cardiac arrest during transport.

Determine the algorithmic next step for unstable suspected PE.

Bedside transthoracic echocardiography is required.

Current guidelines dictate that if a patient with suspected massive PE is too unstable for a CT scan, bedside echocardiography should be performed to detect right ventricular overload and guide emergent reperfusion therapy.

Analyze the arterial blood gas using Winter's formula to rule out other primary interventions.

Expected PaCO2 = (1.5 × 16) + 8 = 32 mm Hg. The actual PaCO2 is exactly 32 mm Hg.

This confirms a pure, fully compensated high anion gap metabolic acidosis (lactic acidosis from tissue hypoperfusion). There is no primary respiratory acidosis or indication for sodium bicarbonate; the treatment is restoring perfusion.

Key Concept

Algorithm for massive pulmonary embolism in hemodynamically unstable patients

Estimated Time:1m 30s

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