What are the key diagnostic criteria for compartment syndrome in a trauma patient?

Diagnosing Compartment Syndrome

Diagnose compartment syndrome primarily through clinical examination focusing on pain out of proportion to injury and pain with passive muscle stretch; measure compartment pressure only when clinical diagnosis remains uncertain, particularly in obtunded or uncooperative patients. 1

Clinical Diagnosis: The Primary Approach

The diagnosis is fundamentally clinical, not based on pressure measurements or imaging. 1 The key is maintaining a high index of suspicion in at-risk patients and performing serial examinations. 2

The "6 Ps" Clinical Signs

Evaluate for these findings in order of appearance:

• Pain out of proportion to injury - This is the earliest and most reliable warning sign 1, 3
• Pain with passive stretch of the affected muscle compartment - Considered by some as the most sensitive early sign 1
• Pressure/tension - Increasing firmness of the compartment as intracompartmental pressure rises 1
• Paresthesia (numbness/tingling) - Results from nerve ischemia 1, 3
• Paresis (weakness/paralysis) - A late sign indicating significant tissue damage 1, 3
• Pulselessness and pallor - These are late signs indicating arterial occlusion and irreversible damage; waiting for these signs is a critical error 3, 1

Diagnostic Accuracy of Clinical Signs

Understanding the limitations of clinical examination is crucial:

• Severe pain alone gives only approximately 25% chance of correct diagnosis 3, 1
• Pain plus pain on passive stretch increases positive predictive value to 68% 3, 1
• Pain plus pain on passive stretch plus paralysis reaches 93% positive predictive value, but by this point irreversible muscle ischemia has likely occurred 3, 1
• Palpation of the suspected compartment is unreliable in isolation (sensitivity 54%, specificity 76% in children) 3, 1
• The absence of clinical signs is more accurate in excluding compartment syndrome than their presence is in making the diagnosis 3

When to Measure Compartment Pressure

Direct measurement is indicated in specific situations where clinical diagnosis is impossible or uncertain:

• Obtunded, confused, or uncooperative patients who cannot report pain 3, 1
• Sedated patients in whom clinical signs cannot be elicited 1
• When clinical diagnosis remains in doubt despite examination 3, 1

Measurement Techniques

Use any of these methods for pressure measurement:

• Traditional needle manometry 3, 1
• Multiparameter monitors (typically used for arterial blood pressure) 3, 1
• Dedicated transducer-tipped intracompartmental pressure monitors 3, 1

Technical pitfall: Using an 18-gauge needle may overestimate compartment pressure by up to 18 mmHg compared to a slit catheter or side-ported needle 3

Pressure Thresholds for Fasciotomy

Apply these criteria when pressure measurement is performed:

• Absolute pressure ≥30 mmHg in the presence of clinical signs 3, 1
• Differential pressure (diastolic BP minus compartment pressure) ≤30 mmHg - This is the most recognized cut-off in current practice 3, 1
• In hypotensive patients: compartment pressure ≥20 mmHg 3
• In unconscious/uncooperative patients: compartment pressure ≥30 mmHg 3

The differential pressure threshold accounts for the fact that tissue perfusion depends on both diastolic blood pressure and intracompartmental pressure. 3 Patients with higher diastolic pressure can tolerate greater compartment pressure increases without tissue ischemia. 3

Continuous vs. Single Pressure Monitoring

• Continuous monitoring may be considered in high-risk, obtunded patients 1
• When combined with differential pressure threshold, continuous monitoring has shown sensitivity up to 94% and specificity of 98% in tibial shaft fractures 3
• There is little evidence that continuous monitoring reduces missed cases compared to serial examination in alert, cooperative patients 3

High-Risk Populations Requiring Heightened Surveillance

Monitor these patients intensively:

• Young men under 35 years with tibial fractures (10-13 times higher incidence) 1, 4
• Tibial shaft fractures (associated with up to 40% of all compartment syndrome cases) 1, 4
• Crush injuries or high-energy trauma 1, 4
• Vascular injuries 1, 4
• Hemorrhagic injuries with significant bleeding into compartments 5, 4
• Patients on anticoagulation 1, 4
• Burns 2

Timing and Monitoring Strategy

Most cases develop within the first 24 hours after trauma, but can occur up to 65 hours post-injury. 5

Recommended Monitoring Protocol

• Every 30 minutes to 1 hour during the first 24 hours in high-risk patients 5
• Extended surveillance beyond 24 hours for crush injuries, hemorrhagic injuries, reperfusion of ischemic lesions, and hypotensive patients 5
• Use scoring charts (such as the UK Royal College of Nursing chart) to maintain heightened awareness among healthcare workers 3

Critical Pitfalls to Avoid

• Never wait for pulselessness and pallor - these indicate irreversible damage and are too late for meaningful intervention 3, 5, 1
• Never rely solely on palpation for diagnosis 3, 1
• Never elevate the limb excessively when compartment syndrome is suspected - this can further decrease perfusion pressure 1
• Never order imaging studies that delay surgical intervention 1
• Never miss compartment syndrome in patients without fractures - it can occur with soft tissue injuries alone 1
• Never delay diagnosis in obtunded patients - measure compartment pressure earlier in these cases 1

Immediate Management When Compartment Syndrome is Suspected

Take these actions without delay:

1. Remove all constricting dressings, casts, or splints immediately 1
2. Position the limb at heart level (not elevated, not dependent) 3, 1
3. Arrange urgent surgical consultation for fasciotomy 1
4. Measure compartment pressures only if diagnosis remains in doubt, particularly in obtunded patients 1

Role of Imaging (Limited)

Imaging has minimal utility in acute compartment syndrome diagnosis:

• Plain X-rays should not be used to rule out compartment syndrome - they are frequently normal or show only increased soft-tissue thickness unless infection and necrosis are advanced 1
• CT has higher sensitivity than plain radiography in identifying early compartment syndrome, showing fat stranding, fluid collections, fascial thickening, and non-enhancing fascia 1
• Ultrasound has no established role in acute compartment syndrome diagnosis 1