A 28-year-old woman is admitted 4 hours after a tibia fracture sustained in a motor vehicle collision. She develops severe pain in the anterior compartment of the leg unresponsive to parenteral analgesia. Examination reveals tense swelling, pain on passive ankle dorsiflexion, and intact dorsalis pedis pulse. A stat compartment pressure measurement shows 45 mmHg (diastolic BP 85 mmHg). What is the most appropriate next step?

Explanation

## Compartment Pressure Interpretation **Key Point:** Compartment pressure of 45 mmHg in a patient with diastolic BP 85 mmHg meets the **delta pressure criterion** for fasciotomy: - Delta pressure = Diastolic BP − Compartment Pressure = 85 − 45 = **40 mmHg** - Fasciotomy is indicated when delta pressure ≤ 30 mmHg - This patient's delta is 40 mmHg (borderline), but combined with **clinical signs** (pain disproportionate, pain on passive stretch, tense swelling), fasciotomy is mandatory. **High-Yield:** Absolute compartment pressure > 30 mmHg + clinical signs = fasciotomy. Do not wait for pressure to rise further or for clinical deterioration. ## Fasciotomy Indications | Criterion | Threshold | Action | |---|---|---| | Absolute pressure | > 30 mmHg | Fasciotomy | | Delta pressure (Diastolic BP − Compartment P) | ≤ 30 mmHg | Fasciotomy | | Clinical signs (pain, swelling, passive stretch pain) | Present | Fasciotomy | | Time since injury | < 8 hours | Fasciotomy if any criterion met | **Clinical Pearl:** This patient has **both elevated absolute pressure (45 mmHg) and clinical signs**—fasciotomy is unequivocally indicated. The presence of intact pedal pulse does not exclude compartment syndrome and should not delay treatment. ## Why Immediate Fasciotomy? ```mermaid flowchart TD A[Tibia fracture + severe pain]:::outcome --> B{Clinical signs of compartment syndrome?}:::decision B -->|Yes: pain out of proportion, passive stretch pain, swelling| C[Measure compartment pressure]:::action C --> D{Pressure > 30 mmHg OR Delta ≤ 30 mmHg?}:::decision D -->|Yes| E[Immediate fasciotomy]:::action D -->|No| F[Observe + repeat pressure in 4-6 hours]:::action E --> G[Surgical decompression prevents necrosis]:::outcome F --> H{Worsening signs?}:::decision H -->|Yes| E H -->|No| I[Continue conservative care]:::action ``` **Warning:** Compartment syndrome causes muscle necrosis within 6–8 hours. At 4 hours post-injury with elevated pressure and clinical signs, the window for tissue salvage is closing. Every minute of delay increases the risk of permanent contracture, rhabdomyolysis, and acute kidney injury.