A 52-year-old woman is brought to the emergency department for sudden-onset severe shortne… — USMLE Step 3

A $52$ -year-old woman is brought to the emergency department for sudden-onset severe shortness of breath, left-sided chest pain, and lightheadedness. She underwent a right total knee arthroplasty $14$ days ago. On arrival, she is visibly distressed, diaphoretic, and confused.

Vital signs are:
Temperature: $37.1^\circ C$ ( $98.8^\circ F$ )
Blood pressure: $72/45$ mmHg
Heart rate: $138$ /min
Respiratory rate: $34$ /min
$SpO_2$ : $84\%$ on $15$ L/min via non-rebreather mask

Physical examination reveals pronounced jugular venous distention. Lung auscultation is clear bilaterally. Heart sounds are rapid with a loud $P_2$ , but no murmurs are appreciated. The right lower extremity is mildly edematous compared to the left.

Point-of-care echocardiography demonstrates a severely dilated right ventricle with a flattened interventricular septum bowing into the left ventricle, diminished right ventricular free wall motion, and a small, hyperkinetic left ventricle.

Which of the following are the most appropriate initial steps in the stabilization of this patient? (Select 2)

Initiation of a continuous norepinephrine infusionAnswer
Administration of systemic alteplaseAnswer
C
Immediate endotracheal intubation
D
Transport to radiology for computed tomography pulmonary angiography
E
Rapid infusion of $2$ liters of intravenous normal saline

Answer

The most appropriate initial stabilization steps are the initiation of a continuous norepinephrine infusion and the administration of systemic alteplase.

This patient presents with a massive pulmonary embolism (PE), characterized by acute PE causing hemodynamic instability (obstructive shock). The clinical presentation of sudden dyspnea following orthopedic surgery combined with point-of-care echocardiography showing right ventricular (RV) dilation and septal flattening (the 'D-sign') provides sufficient diagnostic certainty to initiate life-saving empiric therapy. The immediate goals of stabilization are to support systemic perfusion and relieve RV pressure overload. Norepinephrine is the vasopressor of choice because it increases systemic vascular resistance (improving RV coronary perfusion) and provides inotropic support to the failing RV without significantly increasing pulmonary vascular resistance. Concurrently, systemic thrombolysis (e.g., alteplase) is indicated in massive PE to rapidly reduce the pulmonary arterial clot burden, decrease RV afterload, and restore cardiac output.

Step-by-Step Solution

Identify the underlying pathology.

The patient's recent surgery, acute severe dyspnea, and profound hypotension indicate massive pulmonary embolism (PE) causing obstructive shock.

Recognizing the exact mechanism of shock dictates the specialized stabilization sequence required.

Evaluate point-of-care ultrasound findings.

Echocardiography shows severe right ventricular (RV) dilation and septal bowing (D-sign), confirming acute right heart strain and impending cardiovascular collapse.

In hemodynamically unstable patients, bedside ultrasound provides sufficient diagnostic confidence to initiate definitive empiric therapy without risking transport.

Determine the appropriate hemodynamic and pharmacological interventions.

Norepinephrine must be started to maintain systemic perfusion and RV coronary blood flow. Concurrently, systemic thrombolysis (alteplase) must be administered to dissolve the clot burden.

Standard resuscitative measures like intubation and aggressive fluid boluses are actively harmful in severe RV failure due to their negative effects on venous return and ventricular interdependence.

Key Concept

In massive pulmonary embolism with obstructive shock, immediate stabilization relies on vasopressor support (norepinephrine) and reperfusion therapy (thrombolysis) based on bedside clinical and echocardiographic findings, while avoiding therapies that worsen right ventricular hemodynamics (fluids, positive pressure ventilation).

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