Sandra L. Najarian
PATHOPHYSIOLOGY
Compartment syndromes result from elevated pressures within a confined muscle compartment that result in functional and circulatory impairment of that limb.
External compressive forces on a compartment, such as a tight dressing or cast, or an increase in volume within a compartment, usually from hemorrhage and/or edema, are the mechanisms by which compartment syndrome occurs.
The most common compartments affected are in the leg and forearm.
Tissue perfusion is defined as the difference between arterial pressure and the pressure of venous return, and perfusion diminishes as tissue pressure increases.
Normal tissue pressure is <10 mm Hg.
The exact pressure elevation at which cell death occurs is unclear.
Traditionally, compartment pressures between 30 and 50 mm Hg are detrimental to nerve and muscle if pressures remain elevated for several hours.
The “delta pressure” is the diastolic pressure minus the measured intracompartmental pressure. It is thought to be a better predictor of the potential for irreversible muscle damage.
Hypotensive patients do not tolerate elevated compartment pressures as well as normotensive patients.
CLINICAL FEATURES
Severe and difficult-to-control pain, pain out of proportion to examination, and pain with passive stretch are the hallmarks of this syndrome.
Nerve dysfunction often accompanies the pain and manifests as burning or dysesthesias in the sensory distribution of the nerve.
On clinical examination, the compartment is swollen, firm, and tender to palpation, but the affected limb will maintain color, temperature, and a detectable pulse until late in the course of the disease process.
Untreated compartment syndrome results in muscle necrosis and permanent muscle contracture (Volkmann’s ischemia).
DIAGNOSIS AND DIFFERENTIAL
A high index of suspicion based on mechanism of injury is essential to making the diagnosis, especially in unconscious or obtunded patients.
If the diagnosis is in question after the clinical examination, then direct measurement of the compartment is indicated.
Several commercial devices are available to measure compartment pressures.
A “delta pressure” ≤30 mm Hg is most commonly used to diagnose acute compartment syndrome.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Surgical fasciotomy is indicated once the diagnosis is confirmed.
Administer oxygen, remove restrictive casts or dressings, correct hypotension, and elevate affected limb to the level of the heart while arranging for definitive management.
Functional outcomes are favorable when diagnosis and treatment of compartment syndrome occurs within 6 hours of onset.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 275, “Compartment Syndrome,” by Paul R. Haller.