You're dispatched to an "ankle pain" call. Upon walking into the house, you see a young male sitting on the couch with his leg elevated. He tells you he twisted his ankle yesterday while skateboarding. He went to the emergency department (ED), and the physician told him there were no broken bones. He was told to keep the ankle elevated and take Tylenol as needed. The patient says the pain is intolerable now.
Your physical assessment of the extremity reveals a warm, pink foot and ankle. The posterior tibial and dorsalis pedis pulses are both present. The patient is able to move all of his toes and identify the toe being touched, but he says moving his ankle causes pain to shoot up the front of his leg. Compared with the uninjured ankle, there's no noted swelling or deformity. The patient is transported to the ED with the leg in a neutral position.
You learn from the ED physician later that day that the patient received an emergency fasciotomy to relieve the pressure being caused by compartment syndrome.
Physiology of the Syndrome
Muscle groups are wrapped separately in tissue known as fascia, and each group makes up a compartment. The lower leg has four separate muscle compartments. Compartment syndrome happens when the muscle within a compartment experiences an inflammatory response caused by a traumatic injury: contusion, strain, surgery or compression for a prolonged period of time.
The inflammation and swelling of the muscle increases the pressure within the compartment, because the fascia covering the muscle prohibits expansion. This impinges on the blood supply and forces metabolism without oxygen or anaerobic metabolism. The result of anaerobic metabolism is localized acid accumulation, which damages the vessels and cells in the muscle compartment.
Fluid also leaks into the tissue, which worsens the inflammation, further obstructs the blood supply to the muscle group and increases the swelling. The normal pressure in a muscle fascia is 15 20 mmHg. Once the pressure in the muscle approaches 30 mmHg or higher, this cyclic process cannot stop and within six hours the muscle group will necrose.
Compartment syndrome can occur between two to 48 hours after the initial insult. Emergency treatment is a fasciotomy. A fasciotomy is done by taking a scalpel and cutting an incision through the fascia into the swollen muscle. This relieves the pressure within the compartment and may save the muscle.
Signs & Symptoms of the Syndrome
It can be difficult to identify compartment syndrome. The fascia limits outward swelling so distal circulation isn't affected. Patients will have distal pulses. Because the swelling is confined, there's little visible swelling to the extremity, and there may be no angulation or other deformity. Movement and sensation can also remain intact.
Other less obvious signs and symptoms must be recognized. The hallmark sign of compartment syndrome is pain out of proportion to injury. In other words, the patient may complain of horrible 10 out of 10 pain, but the physical exam may not reveal any gross deformity or injury, like in the case above.
In addition to pain, the patient may complain of paresthesia. This is a tingling and numbing to the extremity. The numbing may be localized depending on the muscle group involved. For example, compartment syndrome in the anterior muscle chamber of the lower leg creates numbing in the webbing between the first and second toe.
The surface area over the affected muscle group will be board-like -- rigid rather than soft. Passive flexion of the toes may cause pain.
The patient may lose point discrimination. Tell the patient to look away, and then touch the patient's skin with one end of a bent open paperclip and then two ends of a bent open paperclip. If they have compartment syndrome, they won't be able to tell if you're touching with one or two points of the paperclip.
In the later stages, the muscle will begin to breakdown in a condition known as rhabdomyolysis. The body will eventually eliminate this broken down muscle tissue through the kidneys, causing dark brown urine. This is known as myoglobinuria.
What to Remember as an EMT
The primary responsibility of the EMT is to recognize these signs and symptoms and consider compartment syndrome as a diagnosis. It's easy to label the patient a hypochondriac. Maintain a high level of suspicion, and take the time to complete a thorough assessment. Remember the "P's" of extremity assessment:
Transport the patient with the extremity in a neural position. Consider administration of pain medication per protocol, knowing the patient may not realize significant pain relief. Even if the pain subsides, understand the muscle is still dying. Relay your concerns to the receiving physician.
Failure to recognize and emergently relieve the pressures associated with compartment syndrome will result in the loss of the muscle.