A 35-year-old male construction worker sustains a crush injury to his right leg after a heavy beam falls on it. He is brought to the emergency department 6 hours post-injury with severe swelling of the leg, pain out of proportion to clinical findings, and tense compartments on palpation. Pulses are intact. Urine is dark brown. What is the most likely immediate life-threatening complication that requires urgent intervention?

Explanation

## Clinical Presentation & Pathophysiology **Key Point:** Crush injuries with compartment syndrome present with the classic **5 P's**: Pain (out of proportion), Pressure (tense compartments), Paresthesia, Pallor, and Pulselessness (late sign). The dark urine indicates myoglobinuria from rhabdomyolysis. **High-Yield:** Compartment syndrome is a surgical emergency requiring fasciotomy within 6–8 hours to prevent irreversible muscle necrosis and subsequent acute kidney injury (AKI) from myoglobin precipitation in renal tubules. ## Why This Is the Answer The constellation of: - Crush mechanism (high-energy trauma) - Pain out of proportion to clinical exam (hallmark of compartment syndrome) - Tense compartments on palpation (elevated intracompartmental pressure) - Dark urine (myoglobinuria from muscle breakdown) ...indicates **acute compartment syndrome with rhabdomyolysis**. This is the most immediately life-threatening complication because: 1. **Tissue necrosis** progresses rapidly (irreversible after 6–8 hours) 2. **Myoglobin precipitation** in renal tubules causes acute tubular necrosis and hyperkalemia-induced cardiac arrhythmias 3. **Requires emergent fasciotomy** to prevent death from AKI or hyperkalemic cardiac arrest ## Management Priorities | Intervention | Timing | Rationale | | --- | --- | --- | | **Compartment pressure measurement** | Immediate | Confirm diagnosis (>30 mmHg or within 30 mmHg of diastolic BP = fasciotomy) | | **Fasciotomy** | <6–8 hours | Prevent irreversible muscle necrosis | | **Aggressive IV hydration** | Concurrent | Maintain urine output >200 mL/h to prevent myoglobin precipitation | | **Urinary alkalinization** | Concurrent | Sodium bicarbonate to increase myoglobin solubility | | **Monitor K^+^, ECG** | Continuous | Detect hyperkalemia-induced arrhythmias | **Clinical Pearl:** Pain out of proportion is the **earliest and most sensitive sign** of compartment syndrome. Do not wait for pulselessness (a late sign indicating irreversible damage). [cite:Rockwood & Green's Fractures in Adults Ch 1]