By Christopher Ebright

Case

You respond to an accident involving a semi-truck that drove off a bridge five hours ago and fell approximately 50 feet onto a set of railroad tracks. The driver, who fell asleep at the wheel, is still entrapped within the cab. His lower extremities, from the hip down, are still pinned in the wreckage.  What are your management priorities?

Crush syndrome was first reported in 1910 by German authors who described symptoms including muscle pain, weakness, and brown-colored urine in soldiers rescued after being buried in structural debris (1). Causes range from natural disasters that cause a building collapse, collapse of land that entraps a patient, a crushing injury from an MVC rollover, to less dramatically, an elderly patient that falls alone at home and lays on the floor, compressing tissue for an extended period of time.

Pathophysiology

Crush syndrome involves a series of metabolic changes that occur from a prolonged, highly compressive injury to skeletal muscle. Generally, in the two to four-hour range, some reversible cell damage occurs. By six hours, irreversible tissue death is evident (2). The more skeletal muscle mass involved, the greater the potential complications could be.

Direct injury from the crushing force causes skeletal cell membrane fracture and the opening of calcium, sodium, and potassium channels. This leads to high volumes of sodium rushing into the cell, pulling extracellular and intravascular fluid along with it. Stagnated blood flow due to compression, causes a local histamine release. The resultant capillary dilation contributes to intravascular volume loss.

The intracellular water level thus dramatically increases and combined with the direct injury, the cell membrane ruptures.  Intracellular contents spill into the surrounding tissue and bloodstream; most notably myoglobin, uric acid, and phosphate. The high extracellular phosphate levels accelerate the calcium influx, quickly resulting in an excessive intracellular concentration. A hyperactivation of lysosomes ensues, increasing the concentration of digestive enzymes inside the cell and hastening the cellular membrane breakdown.

Once the local supply of oxygen runs out due to lack of blood flow, energy production (ATP) diminishes and lactic acid levels increase. The increased uric acid level, combined with the lactic acid pulls massive amounts of intracellular potassium into the extracellular space and bloodstream. Lack of available ATP leads to the shutdown of the sodium-potassium pump. Now, no mechanism exists to remove excess intracellular sodium, nor retrieve the excess extracellular potassium.

To sum it up:  The compressed tissue is now comprised of dead cells. The local bloodstream is volume-depleted with excessively low calcium and sodium levels and contains a high concentration of potassium. It is acidotic and filled with myoglobin and other toxins that will cause multisystem organ damage.

Management

The good news is, while the patient is trapped, the consequences are localized. The major problem is not recognizing the systemic potential effects after extrication. Properly prepping the patient before removing the compressive force is essential. Initial management is similar to other trauma patients.  Address any airway, oxygenation and ventilation issues, but the priorities are IV establishment and medication administration. Fluid, ideally normal saline, should be aggressively infused to correct hypovolemia and counteract acute renal failure from increased levels of intravascular myoglobin. Typically, this is a 1-2 liter bolus, then infused at 1 to 1.5 L/hr (3). Per medical control, sodium bicarbonate, calcium and nebulized albuterol should be administered to counteract metabolic acidosis, hypocalcemia and hyperkalemia. If the injury is isolated to an extremity that is accessible, consider placing a tourniquet above the injured site prior to extrication.

Summary

Crush syndrome is frequently observed because of prolonged entrapment, although cases resulting from brief entrapment have also been reported.

Reperfusion of ischemic tissues spreads cellular toxins into the circulatory system.

The goal of treatment is to anticipate crush syndrome and try to counteract its complications as best as possible.

About Christopher: Chris Ebright is an EMS Education Coordinator with the National EMS Academy in Covington, Louisiana.  He is a Nationally Registered paramedic for over 24 years, providing pre-hospital emergency care ranging from primary EMS response to critical care transportation by land and air.  Chris has also educated first responders, EMT’s, paramedics, nurses and doctors for over 23 years. He holds Bachelor of Education degree from the University of Toledo in Toledo, Ohio and is currently an annual presenter at local, state,and national EMS/Public Safety conferences. He is a self-proclaimed sports, rollercoaster and movie junkie and enjoys traveling as often as possible throughout the United States.