Dehydration decreases blood volume to the point where there's not enough blood for both the skin and internal organs, including the brain. The body must make a choice and it chooses the organs and muscles so the blood to the skin is shut off and the body Temperature rises uncontrolled.

HEAT STROKE
Heatstroke doesn't just happen, your lungs "catch fire," breathing becomes short and labored, your mouth becomes parched, your vision blurs, your skin may be dry and clammy, and there may be dizziness and nausea with irrational thoughts and/or actions and the victim's tentative may rise as high as 110°F. By this time the brain is being "cooked" and can be severely damaged. Blood volume, already less than normal, continues to decrease to the point shock may set in. Since the elevated Temperature keeps the blood from clotting, blood may leak into the liver, kidneys and brian. Death may occur unless immediate medical attention is received.

HEATSTROKE SYMPTOMS
An abrupt onset is sometimes preceded by prodromal headache, vertigo, nausea and fatigue, small pupils and very high fever. The victim may become extremely disoriented or unconsciousness with possible convulsions. Sweating is usually but not always decreased, the skin is hot, flushed, and usually dry (sweating has ceased). The pulse rate may be strong, increase rapidly and may reach 160bpm.

Respirations usually increase, but blood pressure is seldom affected. Disorientation may briefly precede unconsciousness or convulsions. The temperature climbs rapidly to 41°C and the patient feels as if they are burning up. Circulatory collapse may precede death, after hours of extreme hyperpyrexia, survivors are likely to have permanent brain damage. Advanced age, debility, or alcoholism worsens the prognosis.

HEAT STROKE FIRST-AID
If you suspect a canoe mate is suffering from heatstroke, call for medical help IMMEDIATELY! If a heatstroke victim doesn't revive in a few minutes he may be dying! By then, a trained medical person must administer special fluids intravenously.

Remove the victim to a cooler location, out of the sun. Loosen or remove clothing and immerse victim in very cool water if possible. If immersion isn't possible, put the victim in the shock position with his head down and feet up (this will help supply the brain with blood). Pour cool water over the body and fan for quick evaporation and lower body Temperature while rubbing the skin to help open blood vessels in the skin; or use cold compresses-especially to the head & neck area, also to armpits and groin.

Stop if the victim is awake, alert and out of pain. If you drop his temperature TOO quickly you can kill him. Do NOT use an alcohol rub and do NOT give any medication to lower fever, it will not be effective and may cause further harm. It is not advisable to give the victim anything by mouth (even water) until the condition has been stabilized.

Once the victim's condition has stabilized, encourage the victim to drink large amounts of fruit juices and other potassium-rich drinks. Continue to watch the victim for at least an hour. If he becomes unconscious again or starts to complain of headache, nausea or dizziness, repeat the treatment (this means his Temperature is rising again). Recovery depends on heat duration and intensity.

Seek medical attention immediately, and continue first aid to lower Temperature until medical help takes over. The victim should be taken to a hospital as soon as possible after the emergency methods have been started for further management. Temperature should be taken every 10 minutes and not allowed to fall below 38°C to avoid converting hyperthermia to hypothermia. Bed rest is desirable for a few days after severe heatstroke, and temperature lability may be expected for weeks.

HEAT EXHAUSTION
Heat exhaustion is more difficult to diagnose than heatstroke, but its prognosis is far better unless circulatory failure is prolonged. It is due to a loss of water and can come on over several days with tiredness, weakness and malaise. If you continue to lose fluid you may go into shock. 69% of your body's weight is fluid stored. 56% in the cells, 37% outside the cells, and 7% in the blood. Water from sweating, breathing and urinating comes from inside the cells. Even if you need eight glasses of water your cells can supply enough water so that your blood volume remains normal. If you continue to loose water your cells reach a point where they can't give up any more, blood volume drops and you may not have enough blood to circulate effectively so your Temperature rises and shock develops.

Usually heat exhaustion is not an emergency condition but it's presence makes you more susceptible to heatstroke. Simply drink large amounts of water and mineral-rich fluid like fruit juice. Well trained athletes can function well on lower fluid levels because their hearts pump blood more efficiently. Simple dehydration takes place when an athlete sweats heavily. If he doesn't replace his fluids he can develop heat exhaustion in a few hours.

HEAT EXHAUSTION SYMPTOMS
Nausea, fatigue, dizziness, weakness, headache and possibly fever. The skin may be pale and moist with heavy perspiration. The temperature may be low (possibly normal) or weak. Dilated pupils, disorientation or fainting spells.

HEAT EXHAUSTION FIRST-AID
Remove victim to cooler location, out of the sun. Loosen or remove clothing and cool victim with water, fanning for quick evaporation. Use cool compresses especially to head & neck area, also to armpits and groin. Do NOT use an alcohol rub and do NOT give any medication to lower fever (this will be ineffective). Give the victim an electrolyte beverages to sip or slightly salted water (½ teaspoon salt and ½ teaspoon of baking soda per quart/liter of cool, NOT ICY, water, ½ cup every 15 minutes). Do NOT give any liquids containing alcohol or caffeine as these may interfere with the body's ability to regulate it's internal temperature. If the victims' condition does not improve or worsens seek medical attention immediately. Have the victim drink large amounts of fluids (fruit juices are okay).

Treatment is aimed at restoring normal blood volume and improving brain perfusion, thus the patient should be placed flat or with their head slightly down. When they start responding, small amounts of sugar water may be given.

HEAT CRAMPS
Heat cramps are a form of muscle cramp brought on by exertion and insufficient salt. Symptoms include muscle cramps, usually in the abdomen & legs, heavy perspiration, light-heartedness, weakness, and exhaustion.

HEAT CRAMP FIRST-AID
Replace salt and fluid, stretch the muscle. Kneading and pounding the muscle is less effective than stretching and contributes to residual soreness. Follow the same measures as for heat exhaustion.