A 32-year-old male construction worker sustained a crush injury to his right leg when a concrete slab fell on him 6 hours ago. On examination, the leg is swollen, tense, and painful. Passive dorsiflexion of the foot elicits severe pain. Compartment pressure measured at the anterior compartment is 68 mmHg (diastolic BP 85 mmHg). Urine is dark brown. What is the most appropriate immediate management?

Explanation

## Acute Compartment Syndrome (ACS) — Recognition and Management ### Clinical Presentation This patient presents with the classic pentad of compartment syndrome: - Pain out of proportion to clinical findings - Pain with passive stretch (dorsiflexion causes anterior compartment pain) - Paresthesia (implied by crush mechanism) - Pallor and pulselessness (late findings) - Paralysis (late finding) ### Compartment Pressure Assessment **Key Point:** The critical threshold for fasciotomy is when the pressure differential (systolic BP − compartment pressure) drops below 30 mmHg, or absolute pressure >30 mmHg in normotensive patients. In this case: - Compartment pressure = 68 mmHg - Diastolic BP = 85 mmHg - Pressure differential = 85 − 68 = 17 mmHg (<<30 mmHg) → **Fasciotomy indicated** ### Rhabdomyolysis Risk The dark brown urine suggests myoglobinuria from crush injury, indicating rhabdomyolysis with risk of acute kidney injury. ### Management Algorithm ```mermaid flowchart TD A[Crush injury + swelling + pain with passive stretch]:::outcome --> B{Measure compartment pressure}:::decision B -->|Pressure - DBP < 30 mmHg| C[Urgent fasciotomy]:::action B -->|Pressure - DBP > 30 mmHg| D[Conservative management + repeat measurements]:::action C --> E[Prevent tissue necrosis & rhabdo complications]:::outcome D --> F{Symptoms worsen?}:::decision F -->|Yes| C F -->|No| G[Continue monitoring]:::action ``` **High-Yield:** Fasciotomy must be performed within 6–8 hours of symptom onset to prevent irreversible tissue damage. Delay beyond this window results in permanent disability or amputation. **Clinical Pearl:** In crush injuries with rhabdomyolysis, aggressive IV hydration (target urine output 200–300 mL/hr) and alkalinization of urine (sodium bicarbonate to maintain urine pH >6.5) prevent myoglobin precipitation in renal tubules. ### Why Elevation & Ice Are Inadequate Elevation and ice may reduce swelling in soft tissue injury, but they do NOT relieve the pathophysiology of compartment syndrome — the increased intracompartmental pressure that compromises microvascular perfusion. Only fasciotomy decompresses the compartment.