Firefighting tasks, whether carried out in fire combat or during training, requires a tremendous amount of energy and as the human body burns (metabolizes) fuel (calories) it produces a tremendous amount of heat. It's just like that thing we call combustion.
Dehydration and hyperthermia can have serious physical and mental impacts on the individual. According to the Wilderness Medicine Textbook, "Cognitive/mental performance, which is important when concentration, skilled tasks, and tactical issues are involved, is degraded by dehydration and hyperthermia."
Temperature regulation is critical for our survival as the human body has a relatively narrow normal operating range; elevate the body's temperature only a few degrees for any length of time and unintended consequences occur.
The body normally cools itself by sweating. As sweat evaporates from the skin, it lowers body temperature.
Heat-related illnesses, such as heat stroke, occur when your body can't keep itself cool. Particularly on hot, humid days, moisture in the air keeps sweat from evaporating fast enough. When this happens, body temperature can rise and you may start to feel sick.
When a body is encapsulated in our firefighting protecting clothing and SCBA, the sweat/evaporation cycle has effectively been eliminated and body temperature begins to rise. Remember, our protective ensemble is designed to shield us from the thermal effects of interior structural firefighting and to provide a measure of protection in the event of a flashover. Even the top-of-the-line turnout gear allows a very limited amount of that internal heat to dissipate.
Types of heat-related illnesses
Our bodies also have a very narrow normal operating range when it comes to body chemistry, particularly electrolytes, or salts. Electrolyte imbalances can occur from excessive fluid loss through sweating, excessive loss of salts through sweating, or a combination of both. Electrolyte imbalance can manifest itself in three ways: heat cramps, heat exhaustion and heat stroke.
Heat cramps are short, severe cramps in the muscles of the leg, arm or abdomen that can happen during or after heavy exercise in extreme heat. Heavy sweating uses up the body's supply of salts, which causes the cramps. Heat cramps also may be precursor to heat exhaustion.
Heat exhaustion occurs when a person spends time in a hot environment without drinking enough fluids. Symptoms include extreme thirst, fatigue, weakness, clammy skin, nausea or vomiting, and rapid breathing.
Heat stroke is the most serious heat-related illness, and left untreated for even a short time, can cause death or permanent disability. Heat stroke occurs when body temperature rises too rapidly, to as much as 106°F or higher within 10 to 15 minutes. The typical symptoms include red, hot and dry skin, no sweating, and rapid, weak pulse.
A firefighter who suffers a heat stroke attack while wearing PPE is very likely not to present the typical hot and dry skin with no visible sweating. The ensemble has been holding in all that heat and moisture and preventing it from evaporating. Thus, a firefighter suffering from heat stroke may likely present with red, moist skin that is hot to the touch.
Drinking water is a must in order to prevent heat injury. Depending on the heat and activity level, a firefighter may need to drink between a pint and three quarts of water per hour. In hot, dry climates this can total as much as 3 gallons per day.
Many years ago I read a study conducted by the Israeli Defense Forces to determine the most effective liquid for their soldiers to consume to prevent dehydration and to treat cases of heat cramps or exhaustion if they occurred.
The results showed that a tepid liquid (cool, not cold) consisting of one part fruit juice and nine parts water was the best combination for rehydration because soldiers would keep drinking. Ice-cold beverages stimulate nerve endings in the back of the throat and tell the brain that thirst has been quenched, albeit prematurely.
When prevention fails and heat-related illnesses set in, it is important to quickly recognize the signs and apply the proper treatment. Here's a look at how to approach each level of illness.
To treat heat cramps:
- Stop all activity, remove all items of the protective ensemble, particularly the protective hood, and sit quietly in a cool place.
- Drink cool water, a sports drink, or other drinks with no caffeine or alcohol.
- Do not resume activity for a few hours after the cramps go away, since heat cramps can lead to heat exhaustion or heat stroke.
- Get medical help if the cramps do not go away in one hour.
To treat heat exhaustion:
- Perform the first two bulleted items above.
- Sit in front of a cooling fan or mister to help promote sweat evaporation and cool the body.
Heat stroke is a time-critical medical emergency. Get the firefighter to a shady or cool area and call for emergency medical assistance immediately. Until they arrive, do the following:
- Cool the victim as quickly as possible with a cool bath or shower, a spray of cool water from hose, or by wrapping the victim in a cool, wet sheet.
- Check body temperature often and continue cooling efforts until temperature drops to 102°F.
- Do not give any fluids to drink until their body temperature has been lowered.
During heat stroke, the human brain is in damage-control mode. It uses the body's blood supply to get the maximum amount of blood to the surface of the skin and extremities to promote heat dissipation through radiation, conduction (why to use the wet sheet) and convection (why to use moving air from the fan or water sprays).
This massive internal shifting of the blood supply comes primarily from the gut, so anything that's introduced to the stomach (fluid) is likely to come right back up.
As fire officers it is our responsibility to ensure that firefighters stay hydrated during all fire combat and non-combat fire operations to maintain their effectiveness.
It is also important to ensure that the necessary logistics are in place to provide the water and that on-location EMS is readily available.