Beyond the Basics: Crush Injuries and Compartment Syndrome

CEU Review Form Crush Injuries and Compartment Syndrome (PDF)Valid until April 4, 2008

     You respond to the scene of a car versus semi truck. The truck driver is ambulatory without complaints and is being managed by the first responders. As you approach the car, you find the driver trapped under the dashboard and complaining of severe pain to his lower extremities; however, you cannot gain adequate access to his legs. Several hours later, extrication efforts have failed because of the way the victim is trapped within the vehicle. This patient has a great potential for suffering a crush injury or developing a compartment syndrome. In addition to ensuring that the patient has a patent airway, adequate breathing and perfusion, what other concerns do you have for him? What specific emergency care would you provide? Read on for the answers to these and other questions.

PATHOPHYSIOLOGY
     Crush injury (CI) and compartment syndrome (CS) are different processes with similar pathophysiology that are frequently discussed synonymously. A crush injury results from prolonged continuous pressure on large muscles like those of the legs or arms, which results in muscle disintegration. Compartment syndrome can be defined as any condition in which a structure such as a nerve or tendon has been constricted within a space. Compartment syndrome is most often associated with deep tissue injury that results in a restriction of outward swelling caused by a collection of blood in the injured tissue due to the inflexible muscle fasciae. This results in increased pressure within the space and swelling that is concentrated inward toward the injured and uninjured tissues and structures. Compression of the internal structures forces restriction of blood flow because capillaries are compressed by the high compartmental pressures.

     Venous pressure increases and the arterioles spasm, leading to tissue ischemia, swelling and, potentially, tissue necrosis. Think of the pericardial tamponade patient: When the pericardial sac is filled and stretched to the point where it will stretch no more, pressure begins to shift away from the sac and toward the heart until it can no longer fill and contract effectively. This same principle of pressure applies in a crush injury. The skin will only stretch so far. As pressure builds within an extremity, it is eventually transmitted inwardly from the skin to the vessels and other internal structures.

     Although trauma is the most likely cause of CS/CI, it can also occur in non-traumatic situations. An extremity that is compressed for a long period of time beneath the weight of the patient's own body, such as after suffering a stroke, is prone to compartment syndrome. Another cause may be muscle overexertion to the point where rhabdomyolysis develops.

     The most prominent type of body muscle is skeletal muscle. Skeletal muscle cell membrane, also known as sarcolemma, is a key factor in ensuring normal cell function and in maintaining a normal cell structure. The cell membrane contains pumps that move potassium and calcium to the inside of cells and sodium to the outside. These pumps rely on energy in the form of adenosine triphosphate (ATP). Myoglobin, a protein found within the skeletal muscle cell, is responsible for supplying skeletal and cardiac muscles with oxygen. The myoglobin has a greater affinity for oxygen than hemoglobin; thus, oxygen is drawn into the skeletal muscle cells from the blood to be used in normal cell metabolism. The skeletal cell also contains enzymes that are not harmful to the cell itself unless the intracellular calcium level rises. When the calcium level rises, the enzymes become destructive to the cell structure and cause its membrane to leak or rupture.