7.4 Compartment Syndrome & Fasciotomy Indications

Compartment Syndrome & Fasciotomy Indications

Acute Compartment Syndrome (ACS) is a devastating orthopedic emergency characterized by elevated intra-compartmental pressure within a closed osteofascial compartment. As pressure rises, tissue fluid pressure exceeds capillary perfusion pressure, leading to microvascular collapse, cellular hypoxia, tissue ischemia, and irreversible muscle and nerve necrosis. ACS occurs most frequently in the lower leg (anterior compartment) and forearm (flexor compartment) following fractures, crush trauma, high-energy contusions, or reperfusion after arterial repair. Rapid clinical recognition, objective pressure measurement, and immediate surgical fasciotomy are critical to prevent permanent contracture or limb amputation.

Pathophysiology of Compartment Syndrome

Skeletal muscles are divided into non-yielding compartments enclosed by rigid fascial membranes and bone. ACS develops through two primary etiologies:

1. Increased Compartment Content Volume: Internal swelling due to hemorrhage, post-ischemic reperfusion edema, severe crush injury, or fluid extravasation during arthroscopy.
2. Decreased Compartment Enclosure Size: External constriction caused by tight circumferential fiberglass casts, tight splints, overly restrictive elastic dressings, or full-thickness circumferential eschar from thermal burns.

As tissue pressure rises above microcapillary pressure (normally $20-30\text{ mmHg}$), capillary collapse prevents oxygen delivery while venous outflow becomes obstructed. This initiates a vicious ischemia-edema cycle: cellular hypoxia causes endothelial wall leakage, leading to further interstitial edema and progressive elevation of compartment pressure.

Clinical Manifestations: The 6 Ps of Ischemia

Trauma nurses must perform serial neurovascular exams, recognizing that physical signs progress along a predictable temporal line:

Crucial Clinical Rule: The presence of a normal distal pulse does NOT rule out acute compartment syndrome. Capillary perfusion collapses at pressures far below systemic arterial systolic blood pressure ($100-120\text{ mmHg}$). Waiting for pulselessness to diagnose ACS will result in permanent limb disability or amputation.

Objective Measurement and Perfusion Differential (Delta P)

When clinical exam findings are ambiguous or when patients are unexaminable (obtunded, intubated, or under deep sedation), direct intracompartmental pressure (ICP) measurement is performed using a hand-held needle manometry device (e.g., Stryker monitor).

Perfusion Differential (Delta P) Calculation

Historically, an absolute ICP threshold $> 30\text{ mmHg}$ was used to diagnose ACS. Current evidence-based trauma guidelines prioritize the Perfusion Differential ($\Delta P$), which incorporates the patient's systemic blood pressure:

$\Delta P = \text{Diastolic Blood Pressure (DBP)} - \text{Intracompartmental Pressure (ICP)}$

Diagnostic Interpretation

• $\Delta P < 30\text{ mmHg}$: Confirms Acute Compartment Syndrome and serves as a definitive indication for immediate emergency surgical fasciotomy.
• Example: A patient with a DBP of $70\text{ mmHg}$ and a leg compartment pressure (ICP) of $45\text{ mmHg}$ has a $\Delta P = 70 - 45 = 25\text{ mmHg}$. Because $25\text{ mmHg} < 30\text{ mmHg}$, immediate surgical decompression is indicated.

Emergency Nursing Actions for Suspected ACS

Upon suspecting acute compartment syndrome, trauma nurses must immediately carry out four critical interventions:

1. Remove External Restraints: Immediately loosen, bivalve, or remove all tight circumferential dressings, ACE wraps, splints, or fiberglass casts down to bare skin.
2. Position Limb at Heart Level: Maintain the affected extremity at level with the heart.
   • Do NOT Elevate the Limb: Elevation reduces local arterial perfusion pressure, worsening microvascular ischemia.
   • Do NOT Apply Ice / Cold Packs: Cold causes local vasoconstriction, further compromising microvascular blood flow.
3. Notify Surgical Team and Maintain NPO: Contact the orthopedic or trauma surgeon immediately for emergency evaluation; place the patient strictly NPO for emergency operating room transport.
4. Hydration and Myoglobinuria Prevention: Administer IV isotonic crystalloids to maintain high urine output ($> 1-2\text{ mL/kg/hr}$) if rhabdomyolysis is suspected.

Surgical Fasciotomy and Postoperative Management

Surgical decompression must occur within 6 hours of symptom onset to prevent permanent neuromuscular disability (such as Volkmann ischemic contracture).

Lower Leg 2-Incision, 4-Compartment Fasciotomy

The lower leg contains four distinct anatomical compartments: anterior, lateral, superficial posterior, and deep posterior. Complete decompression requires two full-length longitudinal skin and fascial incisions:

• Anterolateral Incision: Decompress both the Anterior and Lateral compartments.
• Posteromedial Incision: Decompress both the Superficial Posterior and Deep Posterior compartments.

Lower Leg Cross-Section & 2-Incision Decompression
 ┌─────────────────────────────────────────────────────────┐
 │ ANTEROLATERAL INCISION                                   │
 │   ├── Decompresses: Anterior Compartment                │
 │   └── Decompresses: Lateral Compartment                 │
 ├─────────────────────────────────────────────────────────┤
 │ POSTEROMEDIAL INCISION                                  │
 │   ├── Decompresses: Superficial Posterior Compartment   │
 │   └── Decompresses: Deep Posterior Compartment          │
 └─────────────────────────────────────────────────────────┘

Post-Fasciotomy Nursing Care

• Wounds are left open; do NOT attempt primary skin closure due to residual swelling.
• Apply negative pressure wound therapy (NPWT / Wound VAC) to facilitate fluid removal and secondary wound approximation.
• Perform continuous neurovascular checks every 1-2 hours.
• Monitor urine output and serum creatinine/potassium to identify and treat rhabdomyolysis and acute kidney injury.