What are the clinical signs, diagnostic criteria, and emergent management for acute compartment syndrome?

Acute Compartment Syndrome: Clinical Recognition and Emergent Management

Clinical Signs and Diagnosis

Pain out of proportion to the injury is the earliest and most reliable warning sign of acute compartment syndrome and should trigger immediate action. 1, 2

The "6 Ps" of Clinical Presentation

• Pain out of proportion is the cardinal early sign, though it only provides approximately 25% positive predictive value in isolation 1
• Pain with passive stretch of the affected muscle compartment is considered the most sensitive early clinical finding 3, 1
• Paresthesias (sensory changes) develop from nerve ischemia 3, 1
• Pressure/tenseness of the compartment increases as intracompartmental pressure rises 3, 1
• Paresis (motor deficits) is a late sign indicating significant tissue damage 3, 1
• Pulselessness and pallor are late signs indicating arterial occlusion and represent a missed diagnosis with likely irreversible damage 3, 1

Diagnostic Performance and Pitfalls

The combination of clinical signs improves diagnostic accuracy progressively: severe pain plus pain on passive stretch increases positive predictive value to 68%, and when pain, passive stretch pain, and paralysis are all present, positive predictive value reaches 93%—but by this point irreversible muscle ischemia has likely occurred 1. Do not wait for late signs such as pulselessness, pallor, or paralysis, as these indicate irreversible tissue damage has already occurred. 3, 1, 4

Palpation alone is unreliable (sensitivity 54%, specificity 76% in children) and should never be used as the sole diagnostic criterion 1. Clinical examination has low sensitivity but high specificity, meaning a negative exam does not rule out compartment syndrome 1.

Diagnostic Criteria and Pressure Measurement

Fasciotomy is indicated when compartment pressure ≥30 mmHg or when differential pressure (diastolic blood pressure minus compartment pressure) is ≤30 mmHg. 1

When to Measure Compartment Pressures

Measure intracompartmental pressures when:

• The diagnosis remains uncertain despite clinical suspicion 1
• The patient is obtunded, confused, sedated, or uncooperative and cannot report pain 3, 1
• The patient is a young child who cannot reliably communicate symptoms 1

Pressure Thresholds for Fasciotomy

• Hypotensive patients: Fasciotomy indicated at pressures ≥20 mmHg 3, 4
• Unconscious/uncooperative patients: Fasciotomy indicated at pressures ≥30 mmHg 3, 4
• Normotensive patients with positive clinical findings: Fasciotomy indicated at pressures ≥30 mmHg when duration of increased pressure is unknown or >8 hours 3, 4

The differential pressure threshold (diastolic BP minus compartment pressure ≤30 mmHg) is the most recognized cut-off for intervention in current practice 1. Normal compartment pressure is <10 mmHg 3.

High-Risk Populations Requiring Heightened Surveillance

• Young men under 35 years with tibial shaft fractures represent the highest risk group (tibial fractures account for 4-5% of all ACS cases) 1, 4
• Crush injuries and high-energy trauma 3, 1
• Vascular injuries (particularly when combined with fractures, creating extremely high-risk scenarios) 1, 4
• Patients on anticoagulation 3, 1
• Burns, penetrating trauma, and tourniquet use 3, 1
• Intramedullary nailing procedures 3, 4

Emergent Management Algorithm

Immediate Actions (Do Not Delay for Consultation)

1. Remove all constricting dressings, casts, splints, or bandages immediately 1, 4
2. Position the limb at heart level—avoid elevation as this reduces arterial inflow and worsens perfusion 3, 1, 4
3. Obtain immediate orthopedic surgery consultation—this is a time-sensitive surgical emergency 4
4. Measure compartment pressures only if diagnosis is uncertain, particularly in obtunded patients; do not delay surgical consultation for testing if clinical suspicion is high 1, 4

Definitive Treatment

Emergent fasciotomy of all involved compartments is the definitive treatment and must be performed as soon as the diagnosis is made. 3, 4 The benefits of fasciotomy decrease dramatically and complications increase considerably the later it is performed 3. Irreversible ischemic damage occurs within 6-8 hours of symptom onset 4, 5.

Post-Fasciotomy Management

• Monitor for myoglobinuria and maintain urine output >2 mL/kg/h to prevent acute kidney injury from rhabdomyolysis 1
• Administer sodium bicarbonate to alkalinize urine, as myoglobin is less likely to precipitate in alkaline urine 1
• Consider nephrology consultation for patients developing rhabdomyolysis, particularly with crush injuries, as they may require urgent dialysis for hyperkalemia 4
• Provide diligent wound care and consider negative pressure wound therapy to facilitate closure 1

Critical Pitfalls to Avoid

• Never wait for pulselessness, pallor, or paralysis—these are late signs indicating arterial occlusion and irreversible damage 3, 1, 4
• Never rely solely on palpation for diagnosis (sensitivity only 54%) 1
• Never elevate the limb excessively—this further decreases perfusion pressure and worsens ischemia 1, 4
• Never order imaging studies that delay surgical intervention—diagnosis is clinical, and imaging has no role in acute management 1
• Never delay fasciotomy beyond 6-8 hours from symptom onset, as irreversible muscle and nerve damage occurs rapidly 4, 5
• Do not miss compartment syndrome in patients without fractures—soft tissue injuries alone can cause ACS 1