A 54-year-old woman is brought to the emergency department by her husband due to a severe … — USMLE Step 2 CK

A 54-year-old woman is brought to the emergency department by her husband due to a severe headache, blurry vision, and worsening shortness of breath over the past 48 hours. She was diagnosed with diffuse cutaneous systemic sclerosis 3 years ago. Her current medications include mycophenolate mofetil, low-dose prednisone, and omeprazole. Her temperature is 37.0°C (98.6°F), blood pressure is 226/118 mm Hg, pulse is 112/min, and respirations are 26/min. Oxygen saturation is 91% on room air. Physical examination reveals thickened, tethered skin over her face, chest, and proximal extremities. Cardiopulmonary auscultation reveals a prominent S4 gallop and bilateral basilar crackles.

Laboratory results are as follows:

Parameter	Value	Reference Range
Hemoglobin	$9.1 \text{ g/dL}$	$12.0-16.0 \text{ g/dL}$
Platelet count	$98,000/\text{mm}^3$	$150,000-400,000/\text{mm}^3$
Serum creatinine	$3.6 \text{ mg/dL}$ (Baseline: $0.9 \text{ mg/dL}$ )	$0.6-1.2 \text{ mg/dL}$
Blood urea nitrogen	$52 \text{ mg/dL}$	$7-18 \text{ mg/dL}$
Serum sodium	$136 \text{ mEq/L}$	$136-145 \text{ mEq/L}$
Serum potassium	$4.8 \text{ mEq/L}$	$3.5-5.0 \text{ mEq/L}$
Serum chloride	$104 \text{ mEq/L}$	$98-106 \text{ mEq/L}$
Serum bicarbonate	$14 \text{ mEq/L}$	$22-28 \text{ mEq/L}$
Arterial blood gas (room air)	$\text{pH } 7.31, p\text{CO}_2 \text{ } 29 \text{ mm Hg}, p\text{O}_2 \text{ } 62 \text{ mm Hg}$
Serum TSH	$0.9 \text{ } \mu\text{U/mL}$	$0.5-5.0 \text{ } \mu\text{U/mL}$
Serum free T4	$0.6 \text{ ng/dL}$	$0.9-1.7 \text{ ng/dL}$

A peripheral blood smear demonstrates 4 to 5 schistocytes per high-power field.

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

Initiate therapy with captoprilAnswer
B
Administer intravenous furosemide and noninvasive positive-pressure ventilation
C
Administer empiric broad-spectrum intravenous antibiotics
D
Administer an intravenous sodium bicarbonate infusion
E
Initiate therapy with oral levothyroxine

Answer

The most appropriate next step is to initiate therapy with captopril.

The correct approach is to initiate therapy with captopril. This patient is presenting with scleroderma renal crisis (SRC), a life-threatening complication of diffuse cutaneous systemic sclerosis. SRC is characterized by the sudden onset of malignant hypertension, acute kidney injury (AKI), and microangiopathic hemolytic anemia (evidenced by schistocytes and thrombocytopenia on the peripheral smear). The underlying pathophysiology involves acute renal vascular injury leading to ischemia and massive, unchecked activation of the renin-angiotensin-aldosterone system (RAAS). Therefore, rapid RAAS blockade with a short-acting angiotensin-converting enzyme (ACE) inhibitor, such as captopril, is the definitive treatment. Paradoxically, while ACE inhibitors are generally withheld in patients with AKI due to the risk of worsening renal perfusion, they are the standard of care for SRC and are the only medications proven to improve mortality and preserve long-term renal function in this condition.

Step-by-Step Solution

Identify the primary acute syndrome based on the clinical presentation and laboratory findings.

The patient exhibits malignant hypertension, acute kidney injury (AKI), and microangiopathic hemolytic anemia (schistocytes, thrombocytopenia) in the context of diffuse cutaneous systemic sclerosis.

These findings form the classic clinical triad for scleroderma renal crisis (SRC).

Determine the underlying pathophysiology driving the syndrome.

SRC is caused by acute renal vascular intimal proliferation and ischemia, leading to massive, unchecked activation of the renin-angiotensin-aldosterone system (RAAS).

Understanding the RAAS-driven mechanism is essential for selecting the targeted pharmacotherapy to halt the process.

Select the optimal pharmacological intervention to interrupt the disease progression.

A short-acting angiotensin-converting enzyme (ACE) inhibitor, such as captopril, must be administered immediately.

Although ACE inhibitors are typically contraindicated in the setting of acute kidney injury, they are uniquely life-saving in SRC and are the only class of medication proven to restore renal function and prevent mortality in this specific crisis.

Key Concept

Scleroderma renal crisis presents with acute malignant hypertension, acute kidney injury, and microangiopathic hemolytic anemia; it must be treated immediately with an ACE inhibitor (e.g., captopril), even in the setting of acute kidney injury.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic