Abstract
The extremity compartment syndrome is an acute, limb, and potentially life-threatening emergency that occurs when the pressure in a muscle compartment increases to levels that cause reduced tissue perfusion resulting in ischemic damage to the muscles and nerves.
General Principles
The extremity compartment syndrome is an acute, limb, and potentially life-threatening emergency that occurs when the pressure in a muscle compartment increases to levels that cause reduced tissue perfusion resulting in ischemic damage to the muscles and nerves.
The normal muscle compartment pressure is less than 8 mmHg. Increase of the muscle compartment pressure >30–40 mmHg is generally considered a surgical emergency and an indication for fasciotomy. An alternative to the absolute compartment pressure is the compartment perfusion pressure (CPP):
CPP = Diastolic pressure – Compartment pressure
A CPP <30 mmHg often indicates severe soft tissue ischemia and is an indication for an emergency fasciotomy.
Conditions that might cause extremity compartment syndrome include severe fractures, crush injury, ischemia due to vascular injury, venous outflow obstruction, circumferential burns, snake or spider bites, excessive exercise, and constricting bandages or casts. This complication is sometimes observed in unconscious or obtunded patients due to drug or alcohol intoxication and prolonged limb compression. Secondary compartment syndrome may occur in trauma or burn patients receiving massive fluid resuscitation (Figure 10.1, Figure 10.2, Figure 10.3, Figure 10.4).
Figure 10.2 Penetrating trauma to the left lower leg with severe swelling and intense pain. This patient should be evaluated for compartment syndrome.
Figure 10.3 Extensive soft tissue trauma in the buttocks following a violent beating, resulting in compartment syndrome and rhabdomyolysis.
Timely diagnosis and decompressive fasciotomy are critical for limb salvage and prevention of renal failure. Muscle damage and neuropraxia may be reversible if the compartment syndrome is treated early, within four to six hours of the ischemic insult. Ischemia lasting greater than four to six hours more commonly results in irreversible muscle ischemia and axonotmesis. This ischemia can result in muscle necrosis, chronic muscle contracture, sensory deficit, paralysis, and potential limb loss. Delayed treatment of a compartment syndrome causes myoglobinemia and myoglobinuria, which might cause acute renal failure. CPK levels higher than 5,000 units/L are associated with an increased risk of renal failure, especially in elderly patients.
The lower leg is the most commonly affected site, followed by the forearm, thigh, arm, and buttocks.
Clinical Presentation
The clinical examination is often unreliable, especially if performed during the early stages of the compartment syndrome. A high index of suspicion is the cornerstone of early diagnosis.
The classic “six Ps” described in extremity compartment syndrome (pain, paresthesia, pallor, poikilothermia, pulselessness, paralysis) are often not present, especially at the early stages.
Pain out of proportion, often not responding to narcotic analgesia, is the most common and earliest clinical finding. The pain becomes worse with passive stretch of the involved muscles. Paresthesia is a fairly early sign, indicating nerve ischemia. These examination findings, however, may be difficult to elicit in obtunded or otherwise unevaluable patients. For example, after traumatic brain injury or in patients requiring high levels of sedation or paralysis, these clinical exam findings may be difficult to elicit.
The clinical finding of a tense compartment is often operator dependent. Elevated CPK levels in the absence of explanatory diagnosis should raise the suspicion of compartment syndrome and prompt thorough physical examination and quantitative measurement of compartment pressures.
Some of the findings, such as pulselessness, pallor, or paralysis, are late findings, when the extremity becomes less likely to be salvageable.
In order to avoid delayed diagnosis, the evaluating physician should have a high index of suspicion and have a low threshold to request surgical or orthopedic consultation (Figure 10.5 AC).
Figure 10.5 A–C Delayed diagnosis of extremity compartment syndrome: cyanotic appearance of the skin of the right foot (A), delayed capillary refill of the skin the left foot (B), and mottled appearance of the skin of the left foot (C), are late findings of compartment syndrome and are associated with a high risk of muscle necrosis and limb loss.
Investigations
Pulse oximetry on the affected toes or fingers is normal in the early stages of compartment syndrome. An abnormal SaO2 is a late finding.
CPK levels should be performed in patients with extensive soft tissue trauma and in cases with suspected compartment syndrome. Elevated CPK should be monitored serially for trend and prompt the physician to evaluate carefully for extremity compartment syndrome. Very high levels are suggestive of large muscle compartment involvement (e.g., gluteal, thigh compartments).
Progression of compartment syndrome can lead to myoglobinuria in which the urine is dark, brownish, or “red” macroscopically but hematuria is absent on microscopic urinalysis. The patient may go into renal failure with elevation in serum creatinine and BUN. Muscle necrosis and renal failure may also result in hyperkalemia (Figure 10.6).
Measurement of muscle compartment pressures is the definitive diagnostic test and should be considered liberally in suspected cases (Figure 10.7 A–C).
