A 48-year-old man is evaluated in the surgical ward on postoperative day 2 following an op… — USMLE Step 2 CK

A 48-year-old man is evaluated in the surgical ward on postoperative day 2 following an open reduction and internal fixation of a closed, highly comminuted midshaft tibial fracture. Over the past 4 hours, he has complained of rapidly escalating pain in his right leg that is entirely unresponsive to intravenous morphine. His temperature is $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ), heart rate is $128$ /min, blood pressure is $90/55$ mmHg, and respiratory rate is $24$ /min. Physical examination reveals a markedly swollen right lower extremity. The skin surrounding the surgical incision is tense, erythematous, and notably discolored with scattered bullae containing dark fluid. Exquisite tenderness is present well beyond the margins of the erythema. Subcutaneous crepitus is palpable along the medial aspect of the tibia. Dorsalis pedis and posterior tibial pulses are faint but palpable. Laboratory studies show:

Leukocyte count: $28,000$ /mm $^3$
Serum sodium: $129$ mEq/L
Blood urea nitrogen: $34$ mg/dL
Serum creatinine: $1.8$ mg/dL

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

Immediate surgical exploration and radical debridement of the right lower extremityAnswer
B
Direct measurement of intracompartmental pressures in the right lower leg
C
Intravenous administration of broad-spectrum antibiotics and close clinical observation
D
Transport to the radiology suite for magnetic resonance imaging of the lower extremity
E
Lower extremity venous duplex ultrasonography to evaluate for deep vein thrombosis

Answer

Immediate surgical exploration and radical debridement of the right lower extremity

The correct answer identifies that this patient has developed a necrotizing soft tissue infection (NSTI), likely gas gangrene caused by Clostridium perfringens or a polymicrobial synergistic infection, following his orthopedic surgery. The hallmark signs include pain out of proportion to physical findings, rapid progression, hemodynamic instability (septic shock), hemorrhagic bullae, and subcutaneous crepitus (gas production). Laboratory findings of severe leukocytosis, hyponatremia, and acute kidney injury (components of the LRINEC score) strongly support this diagnosis. The definitive and life-saving treatment for NSTI is immediate, aggressive surgical exploration and radical debridement of all necrotic tissue. Broad-spectrum antibiotics are given adjunctively, but surgery must not be delayed.

Step-by-Step Solution

Analyze the clinical presentation and vital signs.

The patient has severe pain, high fever (

39.2^\circ\text{C}

), and hemodynamic instability (BP

90/55

mmHg, HR

128

/min) occurring 2 days after orthopedic surgery.

Identifying systemic toxicity and shock is critical to recognizing a life-threatening postoperative emergency.

Evaluate the local wound findings and laboratory results.

The leg exhibits erythema, dark fluid-filled bullae, tenderness beyond erythematous margins, and crepitus. Labs show severe leukocytosis (

28,000

/mm

^3

), hyponatremia (

129

mEq/L), and acute kidney injury.

Crepitus (gas in tissues), bullae, and hyponatremia are pathognomonic hallmarks of necrotizing soft tissue infection (NSTI), differentiating it from simple cellulitis or compartment syndrome.

Determine the definitive management.

The patient requires immediate transfer to the operating room for radical surgical debridement.

NSTI is a rapidly progressive surgical emergency. Antibiotics alone cannot penetrate necrotic tissue, and any delay for advanced imaging or alternative diagnostic testing drastically increases mortality.

Key Concept

Necrotizing soft tissue infection (NSTI) is a life-threatening surgical emergency characterized by pain out of proportion, systemic toxicity, crepitus, and bullae; it must be differentiated from compartment syndrome in the postoperative orthopedic patient and requires immediate radical surgical debridement.

Estimated Time:1m 30s

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