If someone on your boat complains of weakness, headache, and nausea, your first instinct is probably going to be to hand him a bucket and send him downwind. The symptoms for seasickness and heat exhaustion are nearly identical. This is unfortunate, because while seasickness can be an incredibly unpleasant way to pass some time on the water, heat exhaustion can be far more serious.

"You need to recognize heat exhaustion before it moves into heat stroke," said Dr. Eric Johnson, a Staff Physician at Teton Valley Hospital, in Driggs, Idaho; past president of the Wilderness Medical Society; a NAUI diving instructor; and a Mount Everest base camp physician. "If you go into heat stroke in a marine environment, it's game over."

The medical definition of heat exhaustion includes having a core body temperature between 100.4 and 104 degrees Fahrenheit in the face of heat stress. When core body temperature rises above 104 degrees, you may develop a complex clinical disorder called heat stroke. It is characterized by neurological signs including confusion, seizures and coma. People suffering from heat stroke can go into multi-organ failure. Their liver and kidneys can stop working, their blood can have trouble coagulating and brain damage can occur.

Hyperthermia requires immediate medical attention if it has moved into the heat stroke phase, Johnson says.

"With boating, this is a hydration and prevention issue," says Johnson who spoke at the week-long "Medicine for Mariners and Safety at Sea" conference at The Bitter End Yacht Club on Virgin Gorda in January. "The body has about a 10-degree core temperature range in which it can survive, but we are capable of going to the equator and the Arctic. It's behavioral adaptations that you need to pay attention to. If you're on a boat drinking alcohol all day in the sun on a few hours' sleep, that's not the best behavior for preventing heat illnesses."

THE DANGERS OF HEAT

Most people who die of heat illness are actually on land. About 380 people die each year from heat stroke in the United States, most of them elderly people in their homes during heat waves without access to air conditioning.

Still, according to NOAA statistics, heat illnesses is a leading cause of weather-related fatalities, and heat exhaustion can affect people of any age depending on the air temperature, humidity, physical activity, state of hydration, and other conditions. Plus, doctors say that boating itself can be a predisposing factor, because you're out in the hot sun. . "It's usually a matter of not taking care of yourself at sea," Johnson says. "It really can be that simple. And it's not always about being irresponsible. If you're cruising and your sleep rhythms are off, you have to recognize that as a predisposing factor."

TREATING HEAT-RELATED ILLNESS

The first thing to do if someone is suffering from heat exhaustion is get them out of the sun. "Eliminate the heat stress," in doctor-speak. An air-conditioned cabin is often the only "medical" resource that you will need, and sometimes, a shaded area with a cool breeze will do the trick just as well. Give the person cool or room temperature fluids, but stay away from alcohol and caffeine. Rehydration and removing the heat stress are the keys to recovery.

If the person doesn't quickly begin to show signs of improvement"”generally feeling better, remaining alert and able to answer questions, not becoming drowsy or speaking incoherently"”get on the VHF radio and send an alert that you require immediate medical assistance. The very next phase of heat exhaustion"”and it can come on fast"”is the progression toward heat stroke. .

At this point, the best option you have while awaiting medical assistance is to remove the person's clothes and sponge him with lukewarm water, or squirt the lukewarm water at him with a spray bottle while gently fanning his nude body. This technique has been tested and retested by soldiers working in desert climates, and it has proved as effective as it is simple to perform.

You can also soak bed sheets in lukewarm water and cover the person's naked body in them, and place the person near a fan.

"Just don't use really cold water for sponging or for sheets," Johnson says. "Lukewarm water is ideal. You can even dunk the person in the ocean if that's the only option you have, but remember that they're going to be weak and disoriented at that point, which presents a drowning risk. If you must dunk them in the ocean, have a second person in the water with them to make sure their head stays above the surface. And remember that this is less effective than the spray bottle or sponging technique, which is also a lot safer."

Stopping heat stroke once it starts can only be done in a hospital"”and even in that environment, it is often fatal, Johnson says. Your best bet is prevention of heat exhaustion in the first place, and avoidance of a progression toward heat stroke altogether.