Compartment syndrome

Overview
Compartment syndrome is an acute medical problem following injury or surgery in which increased pressure (usually caused by inflammation) within a confined space (fascial compartment) in the body impairs blood supply, leading to nerve damage and muscle death without prompt treatment.

Causes
Because the connective tissue that defines the compartment does not stretch, a small amount of bleeding into the compartment, or swelling of the muscles within the compartment can cause the pressure to rise greatly. Common causes of compartment syndrome include tibial or forearm fractures, ischemic-reperfusion following injury, hemorrhage, vascular puncture, intravenous drug injection, casts, prolonged limb compression, crush injuries and burns.

When compartment syndrome is caused by repetitive heavy use of the muscles, as in a runner, it is known as chronic compartment syndrome (CCS). This is usually not an emergency, but the loss of circulation can cause temporary or permanent damage to nearby nerves and muscle.

Pathophysiology
Any condition that results in an increase in compartment contents or reduction in a compartment’s volume could lead to the development of an acute compartment syndrome. When pressure is elevated capillary blood flow is compromised. Edema of the soft tissue within the compartment further raises the intra-compartment pressure, which compromised venous and lymphatic drainage of the injured area. Pressure, if further increased in a reinforcing vicious cycle, can compromise arteriole perfusion, leading to further tissue ischemia.

The normal mean interstitial tissue pressure is 25 mmHg (range 20–30 mmHg), and if it is over 50–60 mmHg or below 10mmHg (or below the diastolic blood pressure minus 20–30 mmHg) functional tissue changes can occur e.g tissue necrosis. . Arteries and arterioles are stable at these pressures, however the tissues within the compartment dependent on the capillaries for nutrients suffer hypoxia.

Untreated compartment syndrome mediated ischemia of the muscles and nerves lead to eventual irreversible damage and death of the tissues within the compartment.

Symptoms and signs
The 5 "P's" -- Pallor, paresthesias, pressure, paralysis, and pain on passive extension of the compartment-- are useful in recognition in the latter stages of compartment syndrome. Pain is often reported early and almost universally. The description is usually of deep, constant, and poorly localized and is sometimes described as out of proportion with the injury. The pain is aggravated by stretching the muscle group within the compartment. Paresthesia (alterated sensation e.g "pins & needles") in the cutaneous nerves of the affected compartment is another typical sign. Paralysis of the limb are usually late findings. The compartment may feel very tense and firm as well (pressure). Note that a lack of pulse rarely occurs in patients, as pressures that cause compartment syndrome are often well below arterial pressures.

If any of these occur, return to the Emergency Department immediately, or nearest Hospital.

Diagnosis
CCS can be tested for by gauging the pressure within the muscle compartments. If the pressure is sufficiently high, a fasciotomy may be required. Usually compartment pressures equal to or greater than 30mmHg implies compartment syndrome. Pressures are measured by a pressure transducer attached to a IV catheter and needle.

Treatment
Acute compartment syndrome is a medical emergency requiring immediate surgical treatment known as a fasciotomy to allow the pressure to return to normal.

Subacute compartment syndrome, while not quite as much of an emergency, usually requires urgent surgical treatment similar to acute compartment syndrome.

Chronic compartment syndrome in the lower leg can be treated conservatively or surgically. Conservative treatment includes rest, anti-inflammatories, and stretching. In cases where symptoms persist the condition should be treated by a surgical procedure, subcutaneous fasciotomy or open fasciectomy. Without treatment chronic compartment syndrome can develop into the acute syndrome. A possible complication of surgical intervention for chronic compartment syndrome can be chronic venous insufficiency.

Complications
Failure to relieve the pressure can result in necrosis of tissue in that compartment, since capillary perfusion will fall leading to increasing hypoxia of those tissues. If left untreated, acute compartment syndrome can lead to more severe conditions including rhabdomyolysis and kidney failure.