EXERTIONAL HEAT STROKE AND DEHYDRATION IN SPORT

US Congress designated August ‘Heat Stroke Awareness Month’

HEAT STROKE IN SPORTS, RECREATION AND EXERCISE (SRE): CAUSES, PREVENTION, AND TREATMENT, E. Randy Eichner, M.D., Professor of Medicine, Team Internist, Oklahoma Sooners, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma [Gatorade Sports Science Institute “Sports Science Exchange” Volume 15 Number 3, This article may be reproduced for non-profit, educational purposes]

“Heat stroke is always a risk in summer sports, especially football and running. Heat stroke is typically caused by a combination of hot environment, strenuous exercise, clothing that limits evaporation of sweat, inadequate adaptation to the heat, too much body fat, and/or lack of fitness.

“Early recognition and fast treatment of evolving heat stroke can save lives. Preventing heat stroke hinges on acclimation, hydration, pacing, cooling, and vigilance. Heat stroke is a medical emergency. The life-saving adage is: cool first and transport second.

“Summer football brings grueling workouts in brutal heat. For football players in the dog days, mild heat illness is common and grave heat stroke always a threat (Knochel, 1975).

“Since 1995, on average 3 players a year have died of heat stroke. Heat stroke also threatens runners and other athletes; in the 2001 Chicago Marathon, a young man in his first marathon collapsed of heat stroke at 26 miles and died soon after.

“Heat illness can advance quickly in football players and runners, and early warning signs of heat stroke can be subtle. Yet early diagnosis and proper therapy can save lives; exertional heat stroke should be preventable.

Overmotivated Athletes can overheat by doing too much too fast or trying to endure too long or suddenly in both seasoned and rookie Athletes and persons in training. Speed and metabolic rate influence body temperature (measured rectally) in distance racing (Noakes et al., 1991).

A soldier died of heat stroke marching at night, carrying extra weight. He completed just 2.5 miles (Assia et al., 1985). Running generates about twice the heat of marching. Of 82 heat-stroke cases in Israeli soldiers, 40% were from brief exercise, as in the first three miles of a run. Overmotivation was a risk factor (Epstein et al., 1999).

Football breeds a warrior mentality. Victims of heat stroke are described as ‘the hardest worker’ or ‘determined to prove themselves’. “During a hard practice on a hot day, the never-quit mentality can work against a player.” The 1-2 Punch.

“Most heat-stroke deaths in football occur on Day 1 or 2 of two-a-days. A similar 1-2 punch applies in the military. In studying 1,454 cases of heat illness in Marine-recruit training, researchers implicated heat stress on the prior day as a factor (Kark et al., 1996). So a prime time for heat stroke is the day after an exhausting and dehydrating day in the heat.

In summer sports, both heat and humidity contribute to heat illness and heat stroke. In football, body temperature rises in a ‘sawtooth line’, ever higher the longer practice continues. So during a hard practice in full gear, heat stroke is possible at any combination of ambient temperature above 80 °F (26.7 °C) and relative humidity above 40% (Kulka & Kenney, 2002).

Acclimation to heat and humidity,’getting fit’ takes time. Lack of acclimation is a cardinal predictor of heat stroke in football. Acclimation, much of which occurs in a week or two, leads to better drinking and the body holds onto water and salt, increasing blood volume so the heart pumps more blood at a lower heart rate. Heat-fit athletes also sweat sooner, in greater volume, and over a wider body area, so they stay cooler.

Athletes in the heat can sweat 1 to 2 L of fluid an hour. Most athletes drink less than they sweat. The result is dehydration. Dehydrating only 2% body weight, just 5 pounds in a 250-pound linebacker can impair physical performance (Walsh et al., 1994). “Dehydration increases heart rate and decreases cardiac output. Perceived exertion of the work increases as dehydration drains mental sharpness and willpower along with muscle power and endurance. Dehydrated players also heat up faster (Latzka & Montain, 1999).” However, several Athletes have the ability to play through heat illness and succumb to heat stroke.

The football uniform insulates players. As more gear is added from shorts and shirt to pads and helmet to full uniform players heat up faster, get hotter, and cool slower (Kulka & Kenney, 2002). Runners too should avoid vapor-impermeable clothing that limits sweat evaporation.

“Fat athletes are prone to heat stroke. Extra fat is an extra load, increasing exertional heat production.” Extra fat is not the only bulk problem. When a 270-pound player adds 30 pounds of muscle, he can generate more heat, but he does not add enough extra skin surface area to shed or dissipate that extra heat.

“Physical fitness, especially aerobic fitness, confers some of the same physiologic benefits as heat acclimation (Latzka & Montain, 1999). Fitness also makes workouts less taxing. So football players who come to camp fit are at lower risk of heat stroke.”

“In contrast, lack of fitness increases risk of heat illness. In a study of 391 cases of heat illness in Marine recruits, time to run 1.5 miles (and body mass index) predicted risk. A recruit unable to run 1.5 miles in 12 minutes (and with a body mass index over 22) had eight times the risk of heat illness in basic training as did one with a lower body mass and faster run time (Gardner et al., 1996).”

“Supplements and stimulants speed heat buildup. Products that speed players up heat them up. Amphetamine and cocaine are the most dangerous, but ephedra is the most prevalent. Many dietary supplements tout ephedra for weight loss or quick energy. But ephedra poses many health risks, including heat stroke. Heat-stroke risk is compounded by drugs that impair sweating, like some antihistamines, antispasmodics, and medications for depression.”

“Heat stroke in football sometimes hits with surprising speed. When this happens, a common theme of bewildered staff is, “But he got lots of fluids.” The misconception is that hydration prevents heat stroke. The truth is that hydrating is critical but not the end all to prevent heat stroke. Stress fluids but think “beyond fluids.” All the factors described above can work together to cause heat stroke.

“Heat stroke is always a threat during hard drills on hot days, especially in hefty players in full gear.”

Early warning signs of impending heat stroke may include irritability, confusion, apathy, belligerence, emotional instability, or irrational behavior, giddiness, undue fatigue, and vomiting.

Paradoxical chills and goose bumps signal shutdown of skin circulation, portending a faster rise in temperature. The player may hyperventilate, breathe hard, just as a dog pants to shed heat; this can cause tingling fingers as a prelude to collapse.

Lack of coordination and staggering are late signs, followed by collapse with seizure and/or coma. Upon collapse, core body temperature can be 108 °F (42.2 °C) or higher.

“The cooler athletes stay, the better they play.”

Prevention should include frequent cooling breaks, shade from sunshine, ice water and misting fans for rest breaks. As the ambient weather temperature rises, practice pace and duration should be reduced and rest breaks increased. Athletes should sit in cold tubs after practice. Practices should earlier and later, with more time between time for rest, recovery, and cooling.

Dehydration can cause heat stroke. Hydration helps prevent heat stroke. It is not necessary to overhydrate the night before or during the hours prior to a long run or practice. Athletes should drink for their needs. “During training have them weigh in before and after a workout and learn to adjust fluid intake to minimize weight loss. If weight loss does occur, rehydration after activity is critical; drink 20-24 ounces of fluid for every pound of weight loss. Also, eat foods with a high water content (fruits & vegetables). A sports drink beats plain water because it has sugars to fuel muscles and brain, flavoring to encourage drinking, and sodium to hold fluid in the body and help replace sweat losses.

“High heat can overwhelm even physically fit and hydrated players. A week or two of moderate physical activity in the heat, say jogging 30-45 minutes a day, can jump-start heat acclimation. Athletes should never go from a sedentary, air conditioned life into a hard-charging summer athletic camp.

“In football, focus on high-risk players, the big guys. Spot subtle signs of physical or cognitive decline. Weight loss the first few days is fluid loss, not fat loss. Dizziness and drop in blood pressure on standing signal fluid and sodium depletion. Urine should resemble lemonade, not apple juice. Weigh before and after practice. Morning weight should be back up, near baseline, and body temperature should be normal before the player takes the field. When in doubt, hold them out.

“In football, limit gear in the heat. Suit-up in stages in summer camp: shorts and T-shirt the first day or two; then add helmet; then shoulder pads and jersey; finally the full uniform. Remove helmet and pads for fitness runs. Boxers and wrestlers should not run in plastic suits to lose weight.

“Start slow. Athletes cannot safely start full tilt in stifling heat. Other than massive bleeding, exercising all-out in extreme heat is the greatest strain on the cardiovascular system. Pace and duration should “start low and build slow.” Don?t drive halfway to heaven on the first day.

“Off-field behavior also counts. Athletes sleeping poorly or ill, especially with vomiting, diarrhea, or fever, are more prone to heat stroke. The same applies to taking diuretics or drinking alcohol. Monitor all medications.

Medical Emergency. Be Prepared, Boy Scout Motto. Teams and Athletes must have an Emergency Action Plan.

Treating Heat Stroke, every minute counts. “When core temperature is very high, body and brain cells begin to die, so fast cooling is vital. Early features are subtle central nervous system (CNS) changes altered cognition or behavior and core temperature over 104-105 °F (40.0-40.6 °C). When an athlete collapses, the best gauge of core temperature is rectal temperature; oral, axillary, or ear-canal temperature will not do. Advanced features are collapse with wet skin, core temperature over 106-107 °F (41.1- 41.7 °C) and striking CNS changes delirium, stupor, seizures, or coma (Roberts, 1998).

“Cool First. Field treatment is fast cooling. No faster way to cool exists than dumping the athlete into an ice-water tub.” A baby swimming pool filled with water and an filled ice chest to be added are imperative eah summer football practice. Totally Submerge the except the head after gear is removed. “Research suggests ice-water immersion cools runners twice as fast as air exposure while wrapped in wet towels (Armstrong et al., 1996). The Marines also use ice-water cooling (Kark et al., 1996). Recent field research with volunteer runners suggests cold water may cool as fast as ice water (Clements et al., 2002).

(Walmart Kiddy Pool with Large Ice Cooler and hose located beside. Dump Ice, Water and Athlete in Kiddy Ice Pool instantly. mbmsrmd)

“Check the athlete every few minutes for rectal temperature, CNS status, and vital signs. Useful is an indwelling rectal probe with a thermometer. To prevent overcooling, remove the athlete from the tub when rectal temperature drops to 102 °F (38.9 °C). An athlete can be cooled from 108-110 °F (42.2-43.3 °C) to 102 °F (38.9 °C) in 15-30 minutes (Roberts, 1998).

“Transport Second. Cool first, transport second. Send the heat-stroke athlete to the hospital after cooling. With fast cooling, survival rate approaches 100% (Kark et al., 1996). In fact, fast cooling can allow athletes to walk away in good health. For example, yearly at the Falmouth Road Race, up to 10-15 runners collapse with temperatures from 106-110 °F (41.1-43.3 °C), but over a decade nearly all such runners, after ice-water immersion, walked away. After cooling, runners are observed for 20-60 minutes to ensure they are drinking fluids and have normal vital signs and good cognition (Roberts, 1998).

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