A 45-year-old construction worker is brought to the emergency department after a trench co… — USMLE Step 3

A 45-year-old construction worker is brought to the emergency department after a trench collapsed, trapping his right lower extremity under heavy debris for 4 hours. On arrival, he is in significant distress due to excruciating pain in his right calf, which he describes as "10 out of 10." The pain is markedly exacerbated by passive dorsiflexion of his toes. Vital signs show a blood pressure of 135/85 mm Hg, heart rate of 110/min, and respiratory rate of 18/min. Physical examination reveals a tense, swollen right calf with tight, shiny overlying skin. Both dorsalis pedis and posterior tibial pulses are palpable and symmetric to the contralateral side. Capillary refill is 4 seconds in the right foot. A urinary catheter is placed, yielding dark reddish-brown urine. Direct manometry of the right anterior compartment demonstrates a pressure of 45 mm Hg. Based on these findings, which of the following interventions are indicated in the immediate management of this patient? (Select all that apply.)

Urgent four-compartment fasciotomy of the right lower legAnswer
Aggressive intravenous isotonic crystalloid resuscitationAnswer
C
Elevation of the right lower extremity above the level of the heart
D
Initiation of a continuous intravenous heparin infusion
E
Delayed surgical decompression pending lower extremity arterial duplex ultrasonography

Answer

The indicated immediate interventions are urgent four-compartment fasciotomy of the right lower leg and aggressive intravenous isotonic crystalloid resuscitation.

This patient has acute compartment syndrome (ACS), evidenced by severe pain out of proportion to the injury, pain on passive stretch, a tense compartment, and a measured compartment pressure of

45 \text{ mm Hg}

(an absolute pressure

> 30 \text{ mm Hg}

is diagnostic). The definitive and limb-saving treatment is an emergent four-compartment fasciotomy. Additionally, his prolonged entrapment and dark urine strongly suggest rhabdomyolysis (crush syndrome), which requires aggressive intravenous crystalloid resuscitation to maintain high urine output and prevent pigment-induced acute tubular necrosis.

Step-by-Step Solution

Diagnose acute compartment syndrome based on clinical signs and direct measurement.

Patient has pain out of proportion, pain on passive stretch, and a compartment pressure of 45 mm Hg.

Absolute compartment pressures

> 30 \text{ mm Hg}

or a

\Delta P

(Diastolic BP - Compartment Pressure)

< 30 \text{ mm Hg}

confirm the diagnosis, mandating emergent four-compartment fasciotomy.

Identify concurrent systemic complications of the prolonged crush injury.

Patient was trapped for 4 hours and has dark reddish-brown urine, indicating rhabdomyolysis and myoglobinuria.

Crush syndrome requires aggressive intravenous isotonic crystalloid fluid resuscitation to maintain high urine output and flush myoglobin, preventing acute kidney injury.

Avoid contraindicated maneuvers that worsen ischemia or delay definitive care.

Do not elevate the limb above the heart, and do not delay surgery for vascular imaging.

Elevation decreases arterial perfusion pressure. The presence of palpable pulses and a diagnostic pressure reading means imaging is unnecessary and delays limb-saving surgery.

Key Concept

Diagnosis and management of acute compartment syndrome and concomitant crush syndrome

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