13.1 Acute Compartment Syndrome & Extremity Trauma

13.1 Acute Compartment Syndrome & Extremity Trauma

Clinical Scenario: A 28-year-old male presents following a motorcycle crash with a closed midshaft tibial fracture. A posterior splint was placed 2 hours ago. He develops escalating calf pain unresponsive to 100 mcg IV fentanyl and 4 mg IV morphine. The right calf is tense and woody. Passive plantarflexion of the great toe elicits extreme pain by stretching the anterior-compartment toe extensors. Dorsalis pedis and posterior tibial pulses are 2+ bilaterally, and light touch is diminished in the first dorsal web space. The acute care nurse practitioner must recognize acute compartment syndrome and obtain immediate surgical assessment and decompression; manometry assists if the diagnosis is uncertain.

Pathophysiology & Etiology of Compartment Syndrome

Acute compartment syndrome (ACS) occurs when tissue pressure within an enclosed osteofascial space exceeds capillary perfusion pressure, precipitating neuromuscular ischemia. Normal resting pressure is 0 to 8 mmHg. Etiologies include:

• Internal Expansion: Displaced fractures (tibia midshaft most common; radius/ulna in forearm), crush trauma, reperfusion edema following arterial reconstruction, expanding hematomas, and fluid extravasation.
• External Constriction: Circumferential casts, tight splints, pneumatic antishock garments, compressive dressings, and full-thickness circumferential eschars.

Capillary perfusion pressure ($\text{CPP}$) equals mean arterial pressure minus tissue pressure ($\text{CPP} = \text{MAP} - P_{\text{tissue}}$). As compartment pressure rises relative to systemic perfusion pressure, venous outflow and microvascular flow are impaired; hypotension makes ischemia possible at lower compartment pressures. Resulting hypoxia accelerates endothelial leakage and myocyte swelling, worsening pressure in a vicious cycle. Ischemic injury progresses with time. There is no safe waiting period or universal time threshold for irreversible injury.

Clinical Signs: The 6 Ps & Diagnostic Pitfalls

Look for evolving signs and perform serial assessments. They may be incomplete or difficult to assess in an obtunded patient.

• Pain Out of Proportion: Disproportionate pain refractory to opioids; the earliest clinical warning.
• Pain with Passive Stretch: An important early warning, elicited by gently elongating muscles coursing through the compartment (e.g., passive toe plantarflexion stretches anterior-compartment extensors, whereas dorsiflexion stretches deep-posterior toe flexors).
• Paresthesias: Sensory loss along nerves traversing the compartment (e.g., deep peroneal nerve compression causing first dorsal web space numbness).
• Pallor & Poikilothermia: Extremity pallor and coolness from capillary hypoperfusion.
• Paralysis: Late sign indicating established neuromuscular necrosis.
• Pulselessness: A late, ominous finding that also requires urgent evaluation for associated arterial injury. Distal arterial pulses persist until late stages because systolic pressure (100 to 140 mmHg) far exceeds compartment pressure (30 to 60 mmHg). Intact pulses never exclude ACS.

IV Infiltration and Extravasation

New pain, swelling, blanching, leakage or impaired infusion near an IV requires immediate assessment. Stop the infusion; if drug extravasation is suspected, leave the catheter initially for aspiration and possible antidote administration, and do not flush the drug into tissue. Identify the agent and estimated amount, mark the affected area, elevate the limb and follow the agent-specific antidote and warm/cold compress protocol. After aspiration, remove a peripheral catheter as directed by that protocol. Vesicants can cause progressive tissue necrosis. Obtain urgent specialist review for ischemia, blistering or worsening pain; tense swelling and pain with passive stretch require assessment for compartment syndrome.

Intracompartmental Manometry & Delta Pressure

For unreliable or equivocal examinations, assess pressures serially with concurrent blood pressure and urgent surgical review. Measure near the injury, commonly within 5 cm of a fracture; clear clinical ACS should not wait for manometry. In the lower leg, all four compartments must be measured independently: anterior, lateral, superficial posterior, and deep posterior.

Perfusion delta pressure ($\Delta P$) incorporates systemic diastolic blood pressure: $\Delta P = \text{Diastolic Blood Pressure} - \text{Intracompartmental Pressure}$

Interpret Pressures With Clinical Findings: A delta pressure≤30 mmHg or elevated absolute pressure supports concern. Use serial measurements and clinical findings together; clear clinical compartment syndrome requires immediate surgical decompression.

In hypotensive patients, absolute thresholds fail; a diastolic BP of 48 mmHg with a compartment pressure of 24 mmHg yields an ischemic $\Delta P$ of 24 mmHg. Immediate management includes bivalving all casts and maintaining the limb at heart level (elevation impairs arterial inflow; dependency increases venous pressure). Surgical therapy requires a complete two-incision four-compartment fasciotomy.

Osteomyelitis: Recognizing Vertebral Infection

Consider vertebral osteomyelitis with new focal back/neck pain plus fever, elevated inflammatory markers or bloodstream infection; fever may be absent. Obtain a neurologic examination, ESR/CRP, two sets of blood cultures and spine MRI. Image-guided biopsy can establish the organism when blood cultures do not provide a sufficient diagnosis. In a hemodynamically stable patient with a stable neurologic examination, obtain microbiologic evidence before empiric antibiotics when feasible. Sepsis, progressive neurologic deficit or suspected epidural compression requires immediate antibiotics and urgent spine/surgical evaluation. Most bacterial native vertebral osteomyelitis is treated with six weeks of targeted parenteral or highly bioavailable oral therapy.

Open Fractures: Gustilo-Anderson Classification & Antimicrobials

Open fractures breach skin and soft tissue, establishing direct communication with environmental pathogens.

Emergency Antimicrobial Regimen

• Timing: Give systemic IV antibiotics immediately, aiming for within one hour of injury.
• Type I & II: Cefazolin 2 g IV q8h (3 g if $\ge 120\text{ kg}$). In severe beta-lactam allergy, give clindamycin 900 mg IV q8h or vancomycin 15 to 20 mg/kg IV.
• Type III: Follow the trauma/orthopedic prophylaxis protocol. AAST recommends gram-positive and gram-negative coverage. Cefazolin plus gentamicin or a ceftriaxone-based regimen are used in some protocols. Assess renal function and stop prophylaxis at the protocol’s short-course endpoint.
• Soil / Agricultural Exposure: Add aqueous penicillin G 4 million units IV q4h for Clostridium perfringens.
• Tetanus: For dirty/major wounds, give a tetanus vaccine (0.5 mL IM; Tdap when indicated) for unknown/incomplete primary vaccination or ≥5 years since the last dose of a completed series. Add TIG 250 IU IM for unknown/incomplete vaccination, HIV or severe immunodeficiency.

Pelvic Ring Disruptions & Hemodynamic Stabilization

Pelvic fractures from high-energy blunt trauma produce lethal retroperitoneal hemorrhage. The Young-Burgess classification guides care: Lateral Compression (LC), Anterior-Posterior Compression (APC, "open book" tearing pubic symphysis and sacroiliac ligaments), and Vertical Shear (VS). Bleeding originates from the presacral venous plexus and bone surfaces in 85% of cases; 15% involves internal iliac artery branches.

Emergency Pathway

1. Pelvic Binder: Apply a circumferential binder centered precisely over the greater trochanters (not iliac crests) to reduce pelvic volume and tamponade venous hemorrhage.
2. Hemostatic Resuscitation: Activate massive transfusion protocol using 1:1:1 blood components (PRBCs, FFP, platelets) and IV tranexamic acid (1 g over 10 min, then 1 g over 8 hr).
3. Advanced Hemostasis: If shock persists, activate the team’s hemorrhage-control pathway for packing and/or angioembolization. Zone 3 REBOA is a selected bridge in experienced centers and must not delay definitive control.