At first, Kevin joked about the accident that left a deep, four-inch gash in his leg. By the time his friends got him to the hospital, however, he felt nauseated, began to shake uncontrollably, and lost the ability to speak. Due to heavy blood loss, Kevin was in shock.

"Shock occurs when blood pressure falls, depriving vital organs of blood and oxygen," says Dr. George Bergus, associate professor in family practice at the University of Iowa College of Medicine. A person in shock needs immediate medical attention. Deprived of oxygen, the organs begin to systematically shut down. As shock deepens, the more vital organs fail. If shock isn't treated, the brain eventually loses its source of oxygen, and within minutes brain damage or even death occurs, Bergus says.

In cases of serious injury, heavy bleeding, heart attack or serious infection, be alert for signs of shock. Warning signals include mental confusion, faintness, nausea, and cold, pale or clammy skin.

If you observe these signs, take the following steps:

• Lay the person down and raise the feet slightly. Gravity works against blood flow to the brain and upper body.
• Loosen any tight clothing.
• Wrap the person in a blanket to prevent heat loss.
• Seek immediate medical attention.

Because the stomach and kidneys are among the first organs to shut down during shock, avoid giving food and drink if possible, Bergus says.

Doctors treat shock by stabilizing blood pressure with medications that increase the heart rate, constrict large blood vessels, or increase the volume of blood the heart pumps. Once blood pressure is stabilized, the physician is then able to treat the underlying cause, such as bleeding or infection, he adds. Because high blood pressure medication works to keep the heart rate from increasing during stress, people taking these medications are more susceptible to shock if injured, and should be watched closely for warning signals, Bergus says.