Compartment Syndrome

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Core Mechanism: Acute compartment syndrome occurs when there is increased pressure within an enclosed, limited fascial space.
• Cellular Failure: This localized pressure elevation directly compromises the circulation and microvascular perfusion to the tissues within that space, rapidly leading to severe ischemia and subsequent necrosis of the enclosed muscles and nerves.
• The Sequelae: Historically described in 1881 by Richard Von Volkmann, the failure to relieve this ischemic cascade ultimately results in irreversible paralysis and permanent fibrotic contractures (Volkmann's contracture).

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Decompression Maneuvers: The emergency clinician must maintain a high index of suspicion and immediately remove any external compressive forces if vascular compromise or compartment syndrome is suspected.
• Cast Management: If the patient is casted, you must immediately bivalve the cast. Crucial step: It is not enough to just cut the hard fiberglass/plaster; the underlying Webril (padding) and stockinette must also be cut completely down to the skin to fully release the tension.
• Definitive Management: Compartment syndrome is an absolute surgical emergency; initiate prompt surgical/orthopedic consultation for emergent surgical decompression (fasciotomy).
• Resuscitation & Monitoring: In cases associated with crush injuries, monitor closely for rhabdomyolysis and initiate fluid resuscitation to prevent renal failure and manage life-threatening metabolic derangements (hyperkalemia, hypocalcemia, and metabolic acidosis).

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Critical Mimic: Deep Venous Thrombosis (DVT). While compartment syndrome usually presents with pain that worsens gradually since the time of injury, a sudden onset of throbbing pain associated with severe swelling and redness should raise suspicion for a DVT.
• Associated Pathology to Rule Out: Crush Syndrome/Rhabdomyolysis (especially in prolonged entrapment or motor vehicle accidents with cabin intrusion).
• Prioritized Diagnostic Workup:
• Serum Creatine Kinase (CK): A CK level exceeding 10,000 U/L serves as a definitive marker for significant rhabdomyolysis.
• Urinalysis: Look for dark amber urine that tests positive for hemoglobin (indicating myoglobin release).
• Metabolic Panel: Assess for secondary hyperkalemia, hypocalcemia, and coagulation abnormalities.

4. THE VISUAL BOARD (ECG / Imaging / Bedside Signs)

• Radiography (X-ray): Evaluate plain films for the classic high-risk fracture patterns associated with compartment syndrome: tibial shaft fractures (especially from motor vehicle collisions), supracondylar humerus fractures, and forearm fractures.
• ECG Evaluation: If the syndrome is associated with a severe crush injury, explicitly evaluate the ECG for peaked T-waves or widened QRS complexes indicative of hyperkalemia.
• The Limb Exam Checklist: Visually inspect for the amount of edema fluid present, evaluate the color and temperature of the digits, and continuously check capillary refill.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• The "5 Ps" Clinical Framework: The pathognomonic clinical criteria for limb ischemia are the 5 Ps: Pain, Pallor, Paresthesias, Paralysis, and Pulselessness.
• Disposition Criteria: All patients with confirmed or highly suspected compartment syndrome must be admitted for surgical management or to an appropriate inpatient unit for serial observation and re-examination.
• Discharge Criteria (Equivocal Cases Only): Patients with equivocal findings who are discharged must be given strict return precautions emphasizing the immediate return to the ED for worsening pain, new paresthesias, or motor dysfunction.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• The "Pulselessness" Trap: Waiting for the "5 Ps" to appear before consulting surgery is a catastrophic cognitive error. The sources explicitly warn that the 5 Ps seldom occur simultaneously, and their collective presence is a late finding that carries a grave prognosis with irreversible damage.
• The Pediatric Trap: Diagnosis is notoriously difficult in the pediatric population due to challenges with communication, cooperation, and the inability to reliably assess paresthesias or obtain accurate compartment pressures.
• Critical Action: Stretching or actively contracting the ischemic muscle elicits significant pain. Eliciting exquisite pain with passive movement of the affected compartment is the critical physical exam maneuver to identify the syndrome early.

7. MCQ MASTERCLASS (Written Exam Tips)

• High-Yield "Buzzword": "Pain with passive stretch/movement" -> early acute compartment syndrome.
• High-Yield "Buzzword": "Pain that has worsened gradually since the time of injury" and is out of proportion to the visible trauma.
• Most Common Site: The anterior compartment of the lower leg is the most commonly affected anatomical location.
• Associated Fractures: Tibial shaft fractures and pediatric supracondylar humerus fractures (0.1–0.3% risk).
• Exam Distractor: A question may describe a patient with a swollen, painful extremity and state that "distal pulses are bounding." Correction: Intact pulses do NOT rule out compartment syndrome; capillary refill and pulses are frequently maintained until the very late stages of ischemia.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

"I am evaluating a patient who sustained a high-energy tibial fracture in a motor vehicle collision. The patient is complaining of pain that has worsened gradually since the time of injury and is poorly controlled with analgesics. On physical examination, there is exquisite pain elicited by passive stretch of the muscles in the anterior compartment of the lower leg, and the compartment is tense to palpation. Although distal pulses remain palpable and capillary refill is intact, my clinical suspicion for acute compartment syndrome is exceptionally high. I have immediately bivalved the patient's cast, ensuring I cut completely through the Webril and stockinette down to the skin. I am now obtaining an emergent orthopedic surgery consultation for prompt surgical decompression, and I am sending labs including a CK, electrolytes, and urinalysis to rule out concomitant crush syndrome."