The Hazards of Heat

October-November 1999

This is an article from WaveLength Magazine, available in print in North America and globally on the web

by Paul Nicolazzo

It's fall or winter and it's definitely get ting chilly... if not downright cold. You are thinking about flying south to paddle in warm water and sunshine (Hawaii, the South Pacific, Baja, etc.). Stop and give a bit of thought to preventing heat illness during your trip. A little knowledge and preparation can make the difference between an enjoyable experience and an epic one. If you are searching for an epic don't read on. The goal of this article is to prevent them.

Most serious heat related problems occur during periodic 'heat waves' or immediately after an abrupt climatic change (like flying from the cold far north to the hot sunny south). In either case the result is the same if high temperatures, low wind, and high humidity overwhelm your body's ability to cool itself. You can exacerbate the problem by exercising, not eating (restricting your sodium intake), and allowing yourself to become dehydrated. In other words going for that long exposed paddle during the first few days of your South Pacific vacation. Now I'm not saying you should or shouldn't go on that paddle, just that you will likely benefit by making an informed choice and being prepared (yes, I was a boy scout...but it didn't help...I still had to learn the hard way). In order to prevent heat related illnesses you will need to know much more about how your body responds to heat. And what to do when it's overwhelmed.

Heat Illness Flowchart
Major Heat Associated Illnesses
Environmental Conditions	Possible Problems	Signs Symptoms & Related History	Treatment
HOT! moderate to high temperatures possibly with low wind and/or high humidity	Heat Exhaustion	-Core Temp below 105 ° F -Headache Nausea, HOT! -Dark Urine, decreased output -History: not drinking enough water	-Replace Fluids& Electrolytes -Cool -Rest
	Heat Stroke	-Core Temp above 105 ° F -Altered Mental Status or Unconciousness -History: not acclimatized -HOT!	-Stop Excercise -Immediate & Rapid Cooling -Replace Fluids & Electrolytes -Rest
	Dehydration	-Headache, Nausea -Dark Urine, decreased output -History: not drinking enough water	-Replace Fluids & Electrolytes -Rest
	Electrolyte Sickness	-History: drinking a lot of water -History: not eating (esp. foods with Na) -Altered Mental Status or Unconciousness -Clear Urine, increased output	-Replace Electrolytes -Restrict Water -Rest

Your body responds to a heat challenge by dilating surface blood vessels to increase radiant and conductive cooling, and by sweating to increase evaporative cooling. Your ability to effectively dump heat is variable and dependent upon your health and your level of acclimatization. If you are healthy with a good circulatory system, the majority (80%) of the adaptive changes will occur within the first 4- 5 days after you are exposed to an increased heat challenge. Complete acclimatization requires 2-3 weeks. This is why heat waves and abrupt climate changes (like South Pacific vacations) can be so deadly. There is no time for acclimatization. And a good reason why you should consider the length of your trip, the amount of sun and heat to which you will be exposing yourself, the amount of water you can carry, the temperature of the water, wind conditions, etc. before jumping into your boat.

During the acclimatization period, major changes occur in the thermoregulatory centers of your brain, within your peripheral vessels, and within your heart. Sweating, and therefore cooling, is increased and begins at a lower core temperature while electrolyte loss from both sweat and urine is minimized. Metabolic efficiency is significantly increased and more usable energy is produced with less heat. Cardiac output and peripheral vasodilation are increased while the pulse rate is lowered. Essentially your body increases its cooling capacity, produces less heat, and minimizes electrolyte losses as your brain cells become less sensitive to heat. This is a good process...it simply requires time. Most people who suffer from heat related problems do not give themselves enough time to acclimatize.

There are four major heat related problems: dehydration, heat exhaustion, heat stroke, and electrolyte sickness. Dehydration occurs when a person's fluid output exceeds their intake, leaving them lethargic, irritable, and sick. It is not restricted to a hot environment and can occur in any environmental condition. It is a common problem among all outdoor users. Heat exhaustion occurs when a person becomes dehydrated in a hot environment; it is exacerbated by sunburn. As body fluids are lost through sweat and urine (or into the tissue spaces as in sunburn) the individual is unable to maintain their normal cooling processes and they become sick. A person suffering from classic heat exhaustion is pale, lethargic, and sick (often with nausea and vomiting) They may have an increased core temperature or fever (a signal that their cooling systems are failing). If they are not cooled quickly and rehydrated, they may develop heat stroke. Simply put, heat stroke results from a severely increased core temperature (usually above 105F) and the subsequent death of brain cells. If not cooled immediately, your patient will also die. Electrolyte sickness often occurs in a hot environment when an unacclimatized paddler (you) drinks enormous amounts of water without replacing their electrolytes (primarily sodium). The water (in combination with their previous electrolyte loss) further dilutes their blood sodium levels causing muscle cramps and general sickness (the symptoms are similar to heat exhaustion). While it is relatively easy to tell the difference between each of these problems, many people are confused. When you are confronted with this situation, remember that urine, not the amount of fluid intake, is the primary evaluative tool when assessing water balance; it should be clear or pale yellow. If a person is not complaining of the heat and still feels sick, their urine is clear and frequent, and they have been drinking water on a regular basis but not eating foods containing sodium, they are likely suffering from electrolyte sickness (not dehydration or heat exhaustion). If they are HOT, irritable, anxious, dizzyness, lethargic, etc. and their urine is dark, they are suffering from dehydration, heat exhaustion, or heat stroke. Assume heat stroke and begin cooling them immediately. After they are cool, you can assess their hydration status and provide water (and electrolytes) if necessary. Refer to the accompanying charts.

Major Heat Associated Illnesses

Charts by Paul Nicolazzo ©

Because acclimatized individuals sweat more than those who are unacclimatized, they are predisposed to dehydration and heat exhaustion. Because their electrolytes are usually intact, they may be given plain water. Unacclimatized people, because of their inability to efficiently cool themselves, the low tolerance of their brain cells to heat, and their high loss of electrolytes, are predisposed to heat stroke and electrolyte sickness. They should be cooled immediately, rehydrated, and given foods containing sodium and sugar.

As usual, prevention is easier and more fun than treatment. All heat illnesses can be easily prevented. Remember to allow time for the acclimatization process to occur. Acclimatizing your body to a new heat challenge is best accomplished through short peri-ods of exposure (in your case paddling) for a few hours twice a day. Morning and early evening are usually the best times. Do NOT immediately paddle during the hottest part of the day (especially if the water is close to body temperature and there is no wind). Gradually, over a period of days increase the length and exposure of your paddling. Remember that exercise produces heat and increases the heat challenge. Therefore, limit exercise if you (or your friends) are unacclimatized during the first four to five days. Cool people when they become hot (preferably before they become lethargic or irritable). A spray bottle set on mist and sprayed in the air surrounding their head will help anyone keep cool in a dry climate. If you happen to be near one, jumping in a cold stream or river also works quite well. Rolling or swimming in warm ocean water works only when there is a breeze to increase evaporative cooling. When the water is close to normal body temperature no breeze means no effective cooling. Maintain your water and electrolyte balances. Constantly monitor your urine output and color. Drink before you are thirsty (here is where hydro-pacs shine). Cool oral fluids are more easily absorbed than warm or very cold ones. Replace your electrolytes (sodium) as you replace water. Oral electrolyte drinks are okay but all you really have to do is eat salty foods. Salty crackers or lightly salted slices of apple or melon work extremely well and usually taste much better. Sodium is best absorbed with a wee bit of sugar. Salted foods that are mostly fats or proteins slow the absorption of sodium. The first few days in a new heat challenge is NOT the time to restrict sodium. Most importantly, remember to prevent sunburn. Even a slight sunburn causes dehydration and reduces your body's ability to adjust to a heat challenge. Use a high SPF factor sunscreen that is both water and sweat proof. Apply it often and according to the manufacturer's directions. Consider sunblock clothing and wear protective eyewear.

With a wee bit of planning your southern waters vacation can be all you expected it to be and free from any heat illnesses.

Paul Nicolazzo is Director of the Wilderness Medicine Training Institute,
Box 11, Winthrop, WA 98862.