A 65-year-old man is brought to the emergency department by emergency medical services aft… — USMLE Step 3

A $65$ -year-old man is brought to the emergency department by emergency medical services after collapsing at an airport following a $14$ -hour international flight. He has a history of end-stage renal disease and receives hemodialysis three times a week. On arrival, he is in severe respiratory distress, confused, and diaphoretic.

Vital signs are as follows:
- Temperature: $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ )
- Heart rate: $135\text{/min}$
- Blood pressure: $72/40\text{ mmHg}$
- Respiratory rate: $32\text{/min}$
- Oxygen saturation: $82\%$ on room air

Physical examination reveals marked jugular venous distention and cyanosis of the distal extremities. Pulmonary auscultation is clear bilaterally. The physician suspects a massive pulmonary embolism causing acute obstructive shock.

Arrange the following diagnostic and therapeutic management steps in the most appropriate chronological sequence for this patient.

1Administer high-flow supplemental oxygen and establish large-bore intravenous access.
2Initiate intravenous vasopressor therapy to target a mean arterial pressure $> 65\text{ mmHg}$ .
3Perform bedside point-of-care echocardiography to evaluate for right ventricular dysfunction.
4Initiate systemic anticoagulation with intravenous unfractionated heparin.
5Administer intravenous alteplase for definitive systemic thrombolytic therapy.

Answer

The correct sequence for managing massive pulmonary embolism with hemodynamic instability in this patient begins with ABC stabilization, followed by hemodynamic support with vasopressors, bedside echocardiography for diagnosis, unfractionated heparin for anticoagulation (due to ESRD), and finally systemic thrombolysis.

The sequence for managing a massive pulmonary embolism begins with life-saving ABCs and hemodynamic support. Because the patient is unstable, transporting him for a CT pulmonary angiogram is contraindicated; therefore, bedside echocardiography is the appropriate next step to demonstrate right ventricular strain. Once confirmed, systemic anticoagulation is initiated. Notably, because this patient has end-stage renal disease, unfractionated heparin must be used instead of low-molecular-weight heparin to prevent drug accumulation and bleeding. Finally, definitive reperfusion with systemic thrombolytics (alteplase) is administered to dissolve the clot and relieve the obstructive shock.

Step-by-Step Solution

Administer high-flow supplemental oxygen and establish large-bore intravenous access.

Hypoxemia is addressed and a route for emergency medications is secured.

Securing the airway and providing supplemental oxygen mitigates hypoxic pulmonary vasoconstriction, which would otherwise worsen right ventricular strain.

Initiate intravenous vasopressor therapy to target a mean arterial pressure

> 65\text{ mmHg}

Perfusion to vital organs, including the coronary arteries, is maintained.

Hypotension in massive pulmonary embolism rapidly leads to right ventricular ischemia and cardiovascular collapse; immediate hemodynamic support is essential.

Perform bedside point-of-care echocardiography to evaluate for right ventricular dysfunction.

Right ventricular dilation and hypokinesis are identified.

An unstable patient cannot safely travel to a CT scanner. Point-of-care echocardiography is the diagnostic modality of choice to confirm the suspected diagnosis.

Initiate systemic anticoagulation with intravenous unfractionated heparin.

Further propagation of the thromboembolism is halted.

Systemic anticoagulation must be initiated promptly. Low-molecular-weight heparins (like enoxaparin) are contraindicated in end-stage renal disease, necessitating the use of unfractionated heparin.

Administer intravenous alteplase for definitive systemic thrombolytic therapy.

The pulmonary arterial clot burden is rapidly reduced, restoring forward blood flow.

Once right heart strain is confirmed and baseline anticoagulation is addressed, thrombolytics are administered to break down the existing clot and resolve the obstructive shock.

Key Concept

Management of massive pulmonary embolism involves immediate stabilization, bedside echocardiography, and systemic thrombolysis, with unfractionated heparin preferred over low-molecular-weight heparin in patients with severe renal impairment.

Estimated Time:1m 30s

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