Elevated pressures within a confined muscle compartment can lead to functional and circulatory impairment of that limb. The most common compartments affected are in the leg and forearm. An increase in compartment size and volume or external compressive forces can lead to development of this syndrome (Table 176-1).
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Table 176-1 Common Causes of Compartment Syndrome
Vascular puncture in anticoagulated patients
IV/intraarterial drug injection
Soft tissue injury
Prolonged limb compression
Severe and difficult to control pain, pain out of proportion to examination, and pain with passive stretch of the limb are the hallmark symptoms of this disease. Nerve dysfunction often accompanies the pain and is manifested by burning or dysesthesias in the sensory distribution of the nerve. Motor function can be impaired as well. On exam, the compartment is often swollen, firm, and tender to palpation. The 5 P's of compartment syndrome (pain, paresthesias, pallor, poikilothermia, and pulselessness) need not all be present to make the diagnosis. The affected limb can maintain temperature, color, and detectable pulse until late in the disease process. Symptoms may begin within a few hours of the injury or up to 48 hours after the event.
Maintain a high vigilance for this diagnosis, especially in patients with altered mental status or who are sedated. If the diagnosis is considered after the clinical assessment, then directly measure the compartment pressures. Several commercial devices are available to measure compartment pressures. Normal compartment pressure is <10 mm Hg. The exact pressure elevation at which cell death occurs is unclear. Traditionally, any pressure between 30 to 50 mm Hg was felt to be detrimental if left untreated for several hours. The “delta pressure,” the diastolic blood pressure minus the measured tissue pressure, better predicts potential for irreversible muscle damage. A delta pressure ≤30 mm Hg is most commonly used to diagnose acute compartment syndrome. Hypotensive patients do not tolerate elevated compartment pressures as well as normotensive patients. The differential diagnosis for compartment syndrome includes other causes of pain, such as fracture, hematoma, or infection, and other causes of neurologic or vascular compromise once symptoms progress beyond pain only.
Surgical fasciotomy is necessary once the diagnosis is confirmed. While definitive management is being arranged, administer supplemental oxygen, correct hypotension, remove constrictive casts or dressings, and place the affected limb at the level of the heart. Functional outcomes are favorable when diagnosis and treatment of compartment syndrome occurs within 6 hours of its onset.
For further reading in Emergency Medicine: A Comprehensive Study Guide. 7th ed., see Chapter 275, “Compartment Syndrome,” by Paul R. Haller.