Life or Limb
What happens when your leg gets trapped under a building?
Doctors have swarmed to Haiti from around the world to tend to the victims of last week's earthquake, including many whose arms or legs were pinned under steel beams or slabs of concrete. Can you die from a crushed limb?
Yes. If your arm or leg were compressed for less than four hours—two hours if you're elderly or have poor circulation—there is a good chance that doctors will be able to save both your life and your limb. If you manage to survive with a compressed limb for more than eight hours—because you don't have an open fracture and haven't succumbed to fatal blood loss—then you'll almost certainly need an amputation, but the rest of you should be OK. In between those two time frames, emergency doctors face a difficult decision. They can try to save your arm or leg, but the toxins released from its damaged tissues might enter your bloodstream, putting you in grave danger of organ failure.
This all plays out in a chain reaction of systemic effects which doctors call "crush syndrome." During the first phase of crush syndrome, the limb is still trapped under concrete or another material, and thus cut off from blood flow in either direction. As a result, muscle tissue begins to die, and the collapsing cells release proteins, potassium, and lactic acid. These chemicals, which circulate through the body at much lower concentrations under normal circumstances, accumulate in the affected area. (Dead muscles also tend to harden. If the compressed limb exhibits a wooden quality similar to rigor mortis, it's likely to be amputated.)
When the concrete is lifted and circulation is restored, fluid rushes into the affected area to dilute the released electrolytes so their local concentration matches that of the rest of the body. Under normal circumstances, bodily fluids circulate through two spaces—the blood vessels and the insides of cells. But after a crushing injury—or any condition that depletes protein stores like liver failure or malnutrition—the fluid becomes sequestered in an extravascular space. (The process is known as "third spacing.") For some earthquake victims, several gallons of fluid might become sequestered in a swollen, damaged limb in the days following their rescue, resulting in dramatically increased pressure in the affected area and decreased blood pressure in the rest of the body. To prevent hypotension, which can quickly starve vital organs, rescuers often administer fluids to a crush victim through an IV drip even before freeing them. (All of this extra fluid can cause more problems. The blood can become diluted, resulting in anemia.)
While fluids flow into the injured limb, the proteins and potassium flow out into the rest of the body, posing an even greater risk to the victim. Once it gets into the bloodstream, this debris from expired muscle tissue can clog up the kidneys. Typically, one-half of those pulled from collapsed buildings experience some degree of kidney failure, and one-half of those survivors require dialysis. The increased potassium concentration can cause the heart to beat irregularly or stop altogether. Lactic acid—also from the damaged muscle tissue—decreases blood pH, exacerbating the risk of cardiac problems.
The lingering effects of crush syndrome can be deadly even days or weeks after rescue. A study of 18 patients admitted to the intensive-care unit following the 1999 Marmara earthquake in Turkey found that eight did not survive their hospital stay. Doctors in Haiti face a particularly challenging situation. Crush syndrome can be managed if electrolyte levels can be closely monitored. But medical centers were destroyed in the earthquake, modern equipment is scarce, and electricity is hard to come by. As a result, amputation–either in the field or in an operating room—is often the safest option.
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Explainer thanks Jim Holliman of Uniformed Services University of the Health Sciences and Jerry Mothershead of the American College of Emergency Physicians.
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