What is the next step in managing a young adult with severe pain, numbness, and signs of ecchymosis, edema, and tenderness in the left lower extremity after being trapped under a car for several hours, with a negative X-ray and no evidence of fracture?

Immediate Surgical Consultation for Suspected Compartment Syndrome

This patient requires immediate surgical consultation (Option A) to evaluate for compartment syndrome, which is a limb-threatening emergency that can develop after prolonged crush injury and must be diagnosed and treated within hours to prevent permanent disability or limb loss.

Clinical Reasoning

This presentation is classic for evolving compartment syndrome following crush injury:

• Prolonged compression for several hours is a major risk factor for compartment syndrome 1
• Severe pain and numbness are early warning signs—pain (especially with passive stretch) and paresthesia are among the critical "four P's" of compartment syndrome 1
• Ecchymosis, edema, and tenderness indicate significant soft tissue injury with potential for increased compartment pressure 1
• Negative X-ray does not rule out compartment syndrome, which is a clinical diagnosis based on soft tissue injury, not fracture 1

Why Immediate Surgical Evaluation is Critical

Compartment syndrome requires fasciotomy within 4-6 hours of onset to prevent irreversible muscle and nerve damage 1. The skeletal muscle can only tolerate ischemia for approximately 4-6 hours before permanent damage occurs 1.

Key Clinical Signs to Monitor

In patients with crush injury and compartment syndrome risk factors, the following signs should be investigated repetitively (every 30 minutes to 1 hour) during the first 24 hours 1:

• Pain (spontaneous or with passive flexion/extension)
• Tension in the compartment
• Paresthesia
• Paresis
• Compartment pressure >30 mmHg or differential pressure (diastolic BP - compartment pressure) <30 mmHg 1

Critical pitfall: Pulselessness and pallor are late signs that indicate irreversible compartment syndrome—their absence does NOT reassure the clinician 1.

Why Other Options Are Inappropriate

Option B (Pressure Dressing and Ice): Contraindicated

• Applying external pressure to a limb at risk for compartment syndrome can worsen compartment pressures and accelerate tissue ischemia 1
• This intervention could precipitate irreversible damage

Option C (Leg Elevation): Potentially Harmful

• While elevation is sometimes used for simple edema 2, 3, elevating a limb with suspected compartment syndrome can decrease arterial perfusion pressure to an already compromised compartment
• The differential pressure (arterial pressure minus compartment pressure) would be further reduced 1

Option D (Increasing Opioid Dosage): Dangerous Delay

• Escalating pain despite adequate analgesia is a hallmark of compartment syndrome 1
• Simply increasing pain medication masks the critical diagnostic sign and delays definitive treatment
• This represents a dangerous pitfall that can lead to missed diagnosis and permanent disability

Additional Considerations

Rhabdomyolysis Risk

Given the prolonged crush injury, this patient is also at risk for rhabdomyolysis 1:

• CPK levels should be monitored (levels >1000 IU/L indicate rhabdomyolysis) 1
• Aggressive fluid resuscitation may be needed if rhabdomyolysis develops 1

Vascular Injury Assessment

While compartment syndrome is the immediate concern, vascular injury should also be evaluated given the mechanism 1:

• Check ankle-brachial index (ABI <0.9 suggests vascular injury) 1
• Consider CT angiography if vascular injury is suspected 1

The surgical team must evaluate this patient immediately to determine if emergent fasciotomy is indicated, as any delay beyond 4-6 hours significantly increases the risk of permanent muscle necrosis, nerve damage, and potential limb loss 1.