Heat injuries are a significant cause of kidney failure. Heat injuries are generally grouped into two categories--classical heat stroke and exertional heat stroke. Of the two types, exertional heat stroke is more commonly associated with kidney failure. In a 2004 issue of Emergency Medicine Clinics of North America, Dr. Lugo-Amador and his colleagues estimated that “twenty five percent of patients who have exertional heat stroke will develop” kidney failure. Not every person who suffers a heat injury will go on to develop kidney failure, however. A combination of events must occur in the body for a heat injury to lead to kidney damage. According to Drs. Khosla and Guntupalli in their article, “Heat-Related Illnesses,” published in the April 1999 issue of Critical Care Clinics, four separate issues contribute to the development of kidney failure.
The first factor is low blood pressure. In an attempt to cool itself when exposed to extreme heat, the body will increase the amount of sweat being produced. This leads to dehydration and can cause a drop in blood pressure.
The second event that often occurs during an exertional heat injury is the destruction of muscle cells, or thabdomyolysis. Dr. Brown describes this problem in his article entitled “Exertional Rhabdomyolysis,” in the April 2004 edition of The Physician and Sports Medicine. When an athlete is exercising in a hot environment, the body’s energy requirements increase and can exceed its ability to produce energy. When this happens, muscle cells are destroyed and the breakdown products from these cells enter the bloodstream. One of the breakdown products, known as myoglobin, is toxic to the tubules in the kidneys and can directly damage them.
Another problem that contributes to kidney failure when the body undergoes a heat injury is a complex series of events known as disseminated intravascular coagulation (DIC). Dr. Lugo-Amador describes this process in his 2004 article, “Heat-related Illness.” High core body temperature can damage the lining of blood vessels, which can then cause the body’s blood clotting mechanisms to malfunction. Initially this causes excessive blood clotting but eventually leads to abnormal bleeding and damages multiple organs, including the kidney.
The final kidney-damaging issue that arises during an exertional heat injury is decreased blood flow. According to Drs. Yarbrough and Vicario in their chapter entitled “Heat Illness” in Rosen’s Emergency Medicine, in an attempt to lower its core temperature during heat stress, the body will dilate the blood vessels closest to the skin in order to disperse as much heat as possible. Dilating these blood vessels can further drop blood pressure. In an attempt to maintain perfusion to vital organs, the body constricts some other blood vessels, including those which supply the kidneys. This can lead to a dangerous drop in blood supply to the kidneys, contributing to kidney failure.
When an athlete undergoes vigorous exercise in a hot climate, she can become the victim of exertional heat stroke. If the body sustains the four problems described as the result of this heat injury, it can be devastating, and kidney failure can result.