Compartment Pressure Measurement

Compartment pressure measurement (see the image below) is employed in the assessment of potential compartment syndrome, which is a condition of increased pressure within a nonexpansile space that results in compromised tissue perfusion and ultimate dysfunction of neural and muscular structures contained within that space. ^[1]

Compartment syndrome has numerous possible causes, including fractures, crush injury, snake bite, ^[2]  burns, nephrotic syndrome, drug overdose or injection, intravenous (IV) and intraosseous fluid infiltration, and various medications (eg, pressors, anticoagulants, and platelet inhibitors). By far the most common cause, however, is fracture of a long bone. Fractures of the tibia and forearm bones account for most cases. Compressive dressings and casts can also cause compartment syndrome, as in the first case reported by Volkmann. ^[3]

Compartment syndrome can occur within any semirigid anatomic space within the body. The lower leg is the site most frequently affected, followed by the forearm. However, gluteal, ^[4] hand, foot, ^[5] upper arm, thigh, and back compartment syndromes can also occur.

A number of underlying factors may be present that are likely to exacerbate the syndrome and must be treated. These include hypotension, coagulopathy, vascular injury, and artificially created external pressure, such as that imposed by a cast. Definitive intervention is surgical. The clinician must maintain a high index of suspicion in multiply injured, unresponsive, or uncooperative patients so as not to overlook this syndrome and thereby worsen patient outcome. ^{[6, 7]}

Fasciotomy is the treatment of choice. This involves opening the skin and muscle fascia at key points overlying the involved compartment or compartments. The release of enclosed muscles causes a decrease in compartment pressure, thereby improving blood flow to the tissues. ^[6] This procedure is best left to surgeons who have experience in fasciotomy and who will subsequently manage the patient.

A clinical history is the first step in the evaluation of an injury or condition that may produce a compartment syndrome. Clinical examination may confirm the diagnosis in the presence of clear evidence of increased tissue pressure, inadequate tissue perfusion, and loss of tissue function. The diagnosis is less certain when these factors are absent.

Reliance on the presence or absence of the classic five Ps (pain, pallor, pulselessness, paresthesias, and paralysis) may lead to a delay in diagnosis. Patients with a burning quality of pain, delayed onset or increasing severity of pain, or, as classically described, pain on a passive stretch of the compartment must be evaluated for compartment syndrome. As an example, dorsiflexion of the foot causes pain in the posterior calf if its compartment pressure is elevated.

Arterial pulses may persist indefinitely because compartment pressure is almost always less than systolic blood pressure. On examination, the soft tissues are often visibly swollen, and the compartment usually has a tense “woody” feeling on palpation. The presence of fracture blisters suggests increased compartment pressure, but these blisters are not reliably present when compartment pressure is increased. Paresthesias and paralysis tend to be late findings but also merit investigation.

Of the five Ps, the only relatively reliable one is pain. Severe pain that is out of proportion to the injury may be the only early symptom of acute compartment syndrome. Tissue pressure measurements may suggest compartment syndrome, but equivocal measurements still require clinical judgment.

There are three groups of patients in whom clinical findings are difficult to interpret and who may benefit from compartment pressure measurement, as follows (see the image below):

• Unresponsive patients
• Uncooperative patients (eg, children, developmentally delayed, or intoxicated patients)
• Patients with peripheral nerve deficits attributable to other causes (eg, tibial fracture with peroneal nerve injury)

Whitesides et al ^[8] found that fasciotomy was required when the intracompartmental pressure approached 20 mm Hg below the diastolic pressure, whereas McQueen et al ^[9] recommended using a differential pressure (ie, diastolic pressure minus compartment pressure) of less than 30 mm Hg as a criterion for fasciotomy. ^[6]

Compartment pressure measurement has no absolute contraindications. Avoidance of areas with overlying cellulitis is recommended. The procedure itself carries some risk of infection, but this can usually be avoided with appropriate technical practices.