A 38-year-old woman is brought to the hospital 4 hours after a road traffic accident with a comminuted fracture of the right tibia and fibula. Immediate reduction and temporary splinting are performed. On day 3 post-injury, she complains of severe pain in the right leg that is out of proportion to the clinical findings and is not relieved by analgesics. The leg is swollen, skin is tense and shiny, and passive dorsiflexion of the toes causes severe pain. Compartment pressure measured at the anterior compartment is 68 mmHg (diastolic BP 60 mmHg). What is the most appropriate next step?

Explanation

## Acute Compartment Syndrome (ACS) Recognition **Key Point:** Acute compartment syndrome is a surgical emergency characterized by increased pressure within a closed fascial compartment, leading to tissue ischemia and necrosis if not relieved urgently. ## Clinical Presentation — The "5 P's" | Sign | Pathophysiology | |---|---| | **Pain** (disproportionate, not relieved by analgesia) | Ischemic muscle irritation; earliest and most sensitive sign | | **Pressure** (tense, swollen compartment) | Increased interstitial fluid from edema and hemorrhage | | **Paresthesia** (tingling, numbness) | Nerve ischemia | | **Pallor** (pale skin) | Vascular compromise | | **Pulselessness** (late finding) | Complete vascular occlusion; indicates irreversible damage | **High-Yield:** Pain out of proportion to clinical findings + pain with passive stretch of muscles in the compartment = ACS until proven otherwise. This is the most sensitive clinical indicator. ## Compartment Pressure Assessment **Critical Pressure Threshold:** $$\text{Delta P} = \text{Compartment Pressure} - \text{Diastolic BP}$$ In this case: $$\text{Delta P} = 68 - 60 = 8 \text{ mmHg}$$ **Key Point:** When Delta P < 30 mmHg (or compartment pressure > diastolic BP – 30), fasciotomy is indicated. This patient's Delta P of 8 mmHg is critically low and indicates severe ischemic risk. **Mnemonic — Pressure Indications:** **"30 is the key"** — fasciotomy when compartment pressure is within 30 mmHg of diastolic BP. ## Pathophysiology of ACS 1. **Increased compartment pressure** → reduces capillary perfusion pressure 2. **Tissue ischemia** → anaerobic metabolism, lactate accumulation 3. **Increased vascular permeability** → more edema, further pressure rise (vicious cycle) 4. **Muscle necrosis** → rhabdomyolysis, myoglobinuria, acute kidney injury 5. **Irreversible damage** occurs after 6–8 hours of ischemia ## Management Algorithm ```mermaid flowchart TD A[Suspected ACS: pain out of proportion + pain on passive stretch]:::outcome --> B{Compartment pressure measured?}:::decision B -->|No| C[Measure compartment pressure urgently]:::action B -->|Yes| D{Delta P < 30 mmHg?}:::decision D -->|Yes| E[Urgent fasciotomy]:::urgent D -->|No| F[Continue monitoring, repeat pressure if symptoms worsen]:::action C --> D E --> G[Prevent rhabdomyolysis: IV fluids, monitor urine output]:::action G --> H[Delayed closure or skin graft after edema resolves]:::action ``` ## Why Fasciotomy Is Urgent - **Irreversible muscle necrosis** begins at 6–8 hours of ischemia - **Rhabdomyolysis** → myoglobinuria → acute tubular necrosis → renal failure - **Sepsis risk** from necrotic tissue - **Amputation** if fasciotomy is delayed **Clinical Pearl:** Fasciotomy should be performed even if pulses are still palpable — waiting for pulselessness means waiting for irreversible damage. ## Post-Fasciotomy Management 1. **Aggressive IV hydration** — target urine output 200–300 mL/h 2. **Alkalinize urine** — sodium bicarbonate to prevent myoglobin precipitation in renal tubules 3. **Monitor for hyperkalemia** — from rhabdomyolysis 4. **Delayed closure** — leave fasciotomy open; close after 48–72 hours when edema resolves, or use skin graft