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Signs and Symptoms of Heat Illness

Signs and Symptoms of Heat Illness

Defense Centers for Public Health – Aberdeen
Aberdeen Proving Ground, Maryland

Despite effective techniques to prevent heat-related medical conditions, military personnel continue to experience severe and sometimes fatal life-threatening heat-related illnesses during both training activities and combat. As an Army officer and physician in an infantry unit, I have witnessed or treated cases of acute dehydration, heat cramps, heat exhaustion and rhabdomyolysis, which is a serious medical condition where proteins and electrolytes from damaged muscle tissue are released into the bloodstream. I have also treated more severe heat-related cases such as acute kidney failure. Hyponatremia, which is a potentially fatal imbalance of the body’s chemistry caused by excessive fluid consumption, may also occur.

Because heat-related medical conditions in the military tend to be the combined result of warmer weather conditions and physically vigorous activities, they are categorized for medical purposes as exertional heat illness (EHI). The Defense Centers for Public Health – Aberdeen (DCPH-A), formerly known as the Army Public Health Center, tracks and reports the most serious EHI- and weather-related conditions among Soldiers at various installations. Each year, an average of two to three Soldiers die from EHI, and more than 1,000 Soldiers develop an EHI that requires medical attention and/or lost duty time. Military leaders and Soldiers are trained to routinely monitor themselves and their battle buddies for signs of EHI. Milder cases of EHI include heat cramps and heat exhaustion; the most serious cases result in heat stroke, which can be fatal.

While EHIs occur year-round, they begin to increase as the weather gets warmer, especially at temperatures above 75 F. In addition to temperature, it is important to consider the amount of sunlight, humidity and wind speed to determine heat risk. The military uses the Wet Bulb Globe Temperature, known as the WBGT, to characterize heat risk based on these combined climate factors.

The DCPH-A has identified trends in EHI. The highest occurrence of heat casualties occurs at installations where temperatures are warmer and military trainees are conducting outdoor activities. It’s important to be vigilant when monitoring oneself or others as temperatures increase.

What are key risk factors?

Be familiar with the installation’s EHI history in DCPH-A reporting, and assess the risks associated with each planned activity and the current WBGT index. External conditions and the type of activity directly affect the risk level. Also, one should consider individual factors that may increase risk for certain Soldiers, such as:

  • Individual hydration and nutrition are major factors. A battle buddy or sports teammate who fails to hydrate adequately is at much higher risk. Excessive or inappropriate use of nutritional supplements can increase the risk of heat illness. Use of tobacco and alcohol can also increase risk.
  • Individuals who previously experienced an EHI are at greater risk of experiencing additional EHIs, including potentially more serious ones. It is important to know the EHI history of a service member and pay special attention to proper monitoring, hydration and nutrition in these individuals.
  • Individuals who are not acclimatized to local temperatures and high activity levels tend to experience higher rates of EHI than those who are acclimated. For example, younger service members can take as long as 14 days to physiologically adapt to high-temperature environments. It is important to allow new trainees, some of whom may come from cooler climates, sufficient time to adapt to increased activity in the warmer environment.
  • A service member’s physical fitness can also be a risk factor. Higher body fat percentages and poor aerobic fitness, indicated by slow run times, can increase the risk of EHI.
  • Highly motivated service members who push themselves are also at higher risk. Young, very motivated Soldiers who are determined to finish a 12-mile road march in the No. 1 position need to be monitored, as they may ignore their own symptoms.

Example of a stereotypical heat casualty patient

A young male recruit from North Dakota, overweight and with high body fat, arrives for infantry basic training at Fort Benning, Georgia. He is very motivated and exerting exceptional effort because he is slower on group runs than the rest of his platoon. Since the start of training several weeks ago, he has received unwanted attention because of his performance. Intent on improving, he starts using a mix of dietary supplements before workouts.

One morning, his road marching pace is slowing despite the drill instructor encouraging him to keep up with the unit. He continues to slow and finally falls to the ground. His battle buddy stated he first noticed his friend was sweating profusely, and then suddenly, was not sweating at all.

What can be done to reduce this Soldier’s risk of EHI?

  • Monitor his fluid intake. Unit leaders should encourage and monitor hydration for all individuals, especially those with risk factors. Leaders should follow the military’s revised 2022 hydration guidelines appropriate for the activity and not simply force fluid consumption, as overhydration can lead to hyponatremia.
  • Do not let him skip meals in the dining facility or leave large portions of his meal uneaten.
  • Monitor his perspiration during the hardest days of training and be mindful that he may be slowing down because he is approaching exhaustion and not because of poor effort.

Additionally, on weeks and months when the temperatures are highest, unit physical training should be conducted in the early morning, when temperatures tend to be lowest.

Leadership should optimize time in the shade and employ rest breaks during periods of sustained physical exertion in high temperatures. Also keep in mind that service members can sustain heat injuries even in cooler temperatures. Soldiers who wear several layers of clothing for comfort while standing around may find themselves overheating only one or two miles into a long road march while carrying equipment. Unit leaders need to inspect Soldiers’ clothing to ensure they are not hiding warm layers that may increase risk of a heat-related illness.

Additional information and training resources are available on the DCPH-A heat illness prevention and sun safety page at https://phc.amedd.army.mil/topics/discond/hipss/Pages/default.aspx.

Editor’s note: The Defense Centers for Public Health-Aberdeen advances Joint Force health protection with agile public health enterprise solutions in support of the National Defense Strategy. The mention of any non-federal entity and/or its products is for informational purposes only, and not to be construed or interpreted, in any manner, as federal endorsement of that non-federal entity or its products.

  • 26 March 2023
  • Author: USACRC Editor
  • Number of views: 776
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