Almost immediately after a severe burn injury, many physiologic changes occur in the body.

One change involves fluid in the body. After a burn, body fluid moves toward the burned area, which is the reason for some swelling at the burn site.

Some of this fluid is then trapped in the burn area, which means that fluid is not available for use elsewhere in the body. The result is fluid loss in the body.

Fluid is also lost from the burned area in the form of water vapor and seepage. Sometimes, large amounts of water are lost. For the body to function normally again, the lost fluids must be replaced.