Fainting in Heat

http://www.nytimes.com/2013/07/30/health/fainting-in-heat.html

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With temperatures in the Northeast often in the 90s this summer — and the heat index sometimes surpassing 100 degrees — just standing on the street or on a steamy subway platform can place the body under excessive stress. In New York City during the week of July 14, 911 calls were up by 9 percent over the previous year, with many related to the heat, the fire department said.

One common response is heat syncope — or fainting. On the moderate side of the heat illness scale, it is usually set off when a person has been standing for a long period of time, or when he stands up suddenly. In hot weather, blood vessels expand when the body attempts to cool itself. So if someone has been standing for a while, gravity causes his blood to drain downward through the widened blood vessels into the legs and feet. This pooling in the lower extremities diverts blood away from the brain, depriving it of oxygen, and leads to dizziness, lightheadedness and, eventually, fainting. Sufferers usually come-to on their own within 10 to 15 seconds. Their pulse may be weak, but at this stage their body temperature is within the normal range.

To prevent heat syncope from intensifying into a more serious condition, raise the victim’s legs to direct the blood flow to the brain, advised Dr. Dennis A. Cardone, an associate professor in the department of orthopedic surgery at NYU Langone Medical Center and an expert in sports medicine. Next, move him to a shady place and check his airway, breathing and circulation.

When he regains consciousness, give him water or a sports drink, since dehydration can increase the risk for other heat-related maladies. Recovery should occur within an hour, with no additional health problems, Dr. Cardone said. Roni Jacobson