Chapter 10: Heat Induced Injuries Chapter 10
This chapter describes how to recognize and treat health conditions caused by a warm environment and how to help prevent these injuries. Objectives:
Be able to list factors that make someone susceptible to heat illness
Be able to describe the etiology and management of victims with heat cramps and heat syncope
Know the similarities and differences between heat exhaustion and heat stroke
Discuss methods to help prevent heat related illness
Know methods of cooling, which method(s) is best in heat illness, and when to stop active cooling
Be able to list evacuation guidelines for victims with heat illness
Chapter 10: Heat Induced Injuries Three Cases
During a long distance running event, three victims are brought to your first aid station: Victim #1: A 27 year old female “passed out” while standing at a hydration table, where she had stopped to drink some fluids. She wakes shortly after falling to the ground. She is alert and oriented to person, place, time, and event. She denies dizziness, nausea, or weakness and asks if she can continue running. Victim #2: A 42 year old male complains of severe spasms in his right calf muscle. He has been drinking large amounts of pure water throughout the day. Victim #3: A 35 year old is brought to the aid station by bystanders. They state that the victim was moving erratically and “just not acting right.” The victim is obviously confused about the situation. He is covered with sweat, agitated, and warm to the touch. 1. What type of heat illness does each victim have? 2. How should each victim be managed? 3. Can any of these victims continue the race? 4. Who needs to be evacuated immediately?
Risk Factors for Heat Illness Medical Conditions Environmental Conditions
Exercise in a hot environment, particularly if there is high humidity
Lack of air conditioning or proper ventilation
Inappropriate clothing (occlusive, heavy, or vapor-impermeable)
Hot environments (inside of tents or autos in the sun, hot tubs, saunas)
Drugs & Toxins Chapter 10: Heat Induced Injuries
Antihistamines (including diphenhydramine)
Certain motion sickness medications, such as meclizine and dimenhydrinate
Cocaine, amphetamines and other stimulant drugs
Other Risk Factors Types of Heat Illness Heat Cramps
Heat cramps occur when significant salt and water losses are replaced with solutions not containing sufficient salt (sodium chloride or NaCl). Inadequate salt repletion eventually can lead to involuntary contraction of skeletal muscles. Signs of heat cramps include:
Brief, intermittent, involuntary contractions of skeletal muscles.
These cramps most commonly involve the calves, but may occur in any muscle.
Usually only occur in a single muscle or muscle group, and are quite painful.
The victim with heat cramps will classically give a history of:
Attempted hydration, typically with a non-electrolyte containing solution, such as plain water
Oral salt replacement with a 0.1% to 0.2% NaCl solution.
This can be easily made with ¼ to ½ teaspoon of table salt added to a quart of water.
If not responding to the above treatment, the individual may require intravenous fluids and should be evacuated.
Heat Syncope (fainting due to a hot environment)
Syncope is the medical term for “passing out,” usually a brief loss of consciousness. Heat syncope typically occurs when a dehydrated individual stands in a hot environment for an extended period. With standing, blood pools in the legs, decreasing the amount of blood that returns to the heart. This, in combination with dehydration and dilated blood vessels from the hot environment, can decrease blood flow to the brain and cause the individual to faint. Prior to actually losing consciousness, the victim may have the following signs and symptoms:
These symptoms and the actual loss of consciousness usually resolve once the victim is horizontal, as this facilitates redistribution of blood from the legs back to the brain. Treatment Chapter 10: Heat Induced Injuries
The loss of consciousness should be brief, on the order of several seconds up to 2 minutes.
Treatment to improve blood flow to the brain should be instituted
Lie the victim flat on their back (supine)
Elevate the feet to improve venous return back to the heart
Assess the victim for other injuries that may have resulted from the fall
Heat Exhaustion Heat exhaustion is a form of heat illness that results from a significant heat stress. Heat exhaustion is part of a continuum of heat illnesses that progress to heat stroke. Symptoms
Liberal fluid and electrolyte replacement. With heat exhaustion, oral hydration as discussed below is appropriate.
Remove the victim from direct sunlight into a cool, shaded area
If the victim is hyperthermic (> 38 degrees C or 100.4 degrees F), active cooling measures should be taken. In the wilderness, there are limited resources to actively cool a victim.
The best way to cool a hyperthermic victim is through evaporative cooling.
Remove most of the victim’s clothing and make them “sopping wet” with tepid water. While it may seem paradoxical to cool a hyperthermic victim with warm water, the warm temperature of the water helps to prevent the shivering reaction and keeps the skin blood vessels dilated, which allows for heat exchange. Cold water might lead to shivering and constriction of the blood vessels in the skin. However, if only cold water is available, use it.
Fan the victim with anything that will increase air movement across the skin. This air flow will result in evaporation of water from the skin, which cools the victim.
Shivering will increase core body temperature and should be avoided.
Oral hydration should adhere to the following guidelines:
Beverage should not exceed 6% carbohydrate content. Increased carbohydrate content inhibits fluid absorption. You can dilute most sports drinks with water to achieve a better concentration.
A general rule is that every pound lost to sweat should be replenished with 500 mL or 2 cups of fluid.
The treatment goal for mild heat exhaustion should be 1 to 2 liters of oral fluids over 2 to 4 hours.
Chapter 10: Heat Induced Injuries Heat Stroke
Heat stroke is a true medical emergency that is classically defined by the following:
Severe hyperthermia (core temperature > 40°C or 104°F)
Central nervous system (CNS) disturbances such as alteration in the level of consciousness, confusion, or seizures.
However, experience has shown that waiting for the appearance of these three symptoms is too strict and may delay critical treatment.
Any person who has any of the following symptoms in a hot environment should be treated as having heat stroke:
Unsteady gait (often one of the first manifestations of heat stroke)
Diminished or lack of sweating is classically associated with heat stroke; however it is typically a late finding and cannot be relied upon to make an accurate diagnosis. Typically, heat stroke victims will be covered in sweat until very late stages of the illness.
The key to treatment and prevention of heat stroke is in the understanding that heat exhaustion and heat stroke are not separate entities, but are a continuum of the same illness. The onset of any alteration in mental status should alert the BWLS provider that a victim is suffering from significant heat illness.
The primary goal of treatment for heat stroke is to facilitate rapid cooling, which can be accomplished by evaporative cooling as discussed previously.
Additionally, one may place ice packs or cold compresses in areas where large blood vessels are superficial, such as the neck, axilla, groin, and scalp
Most persons will not have rectal thermometer to measure temperature. However, it may be used when one is available:
The goal of treatment is to drop the temperature to below 40°C (104° F) as rapidly as possible
Active cooling efforts should be discontinued around 39°C (102.2°F) to avoid overshoot to a condition of hypothermia, which can occur with very successful cooling efforts.
Drink at least 4-8 ounces of water or sports drink every 15-20 minutes during mild to moderate physical activity, depending on the ambient environmental temperature and humidity.
Hydrate with a goal of clear urine instead of a fixed amount of intake.
Consume salt containing foods or add salt to water if exposed to heat for time periods greater than 2-3 hours, especially if using only water for hydration.
To make a salt solution, add ¼ to ½ teaspoon of table salt to a liter of fluid. Flavored drinks that are cold are more palatable.
Most commercially available sports drinks should be diluted with an equal amount of water for ideal electrolyte concentration.
Chapter 10: Heat Induced Injuries Heat Dissipation
Wear loose fitted clothing that will allow for air circulation and increased evaporation.
Avoid direct sunlight when possible and wear light colored clothing.
Douse with cool fluids or cool misting spray frequently.
Heat acclimatization decreases the incidence of heat injuries and improves performance in hot environments. General guidelines for acclimatization:
Adults should gradually increase the time and intensity of activity in a hot environment over 7 to 10 days.
Children and elders require 10 to 14 days to maximize acclimatization.
Those who are from temperate or cold climates and will be traveling into a hot environment can acclimatize by going into a sauna or steam room for increasing amounts of time each day, beginning 7 to 10 days before making the trip.
De-acclimatization usually occurs within 1 to 2 weeks of being removed from the hot environment. In such a situation, acclimatization must be repeated if necessary.
A victim who suffers a fainting episode thought to be heat-related should only have brief loss of consciousness and recover quickly. Any victim who endures a prolonged loss of consciousness, persistent pre-syncope signs and symptoms upon awakening, more than one episode of passing out, or signs of heat stroke should be evacuated.
A victim with severe heat cramps that do not respond to oral salt solutions, or a person who suffers diffuse and multiple cramps should also be considered for evacuation, depending on the situation.
Heat exhaustion victims may not need to be evacuated:
As long as the victim can adequately be protected from the environment.
In mild cases, close observation in the field for development of heat stroke, as well as cessation of activities for 24-48 hours, is recommended.
If the victim develops behavioral changes, records a temperature above 39°C (102.2°F), or has a fainting episode while under observation, he should be considered a potential heat stroke victim and be evacuated immediately.
Heat stroke is a serious medical emergency, so any victim with signs or symptoms of heat stroke should be evacuated as soon as possible.
Chapter 10: Heat Induced Injuries Questions
1) All of the following increase the risk of heat illness except:
a) Heart disease b) History of heat injury c) Diarrhea d) Alcohol e) All of the above increase the risk of heat injury
2) Heat cramps are most likely to occur in which victim?
a) A runner on a hot day drinking water alternated with a sports drink b) A runner on a hot day not rehydrating with anything c) A runner on a hot day drinking 20 oz of water per hour for several hours d) A runner on a hot day drinking 20 oz of water per hour for 2 hours
3) Which one of the following is the most important difference between heat stroke and heat exhaustion? a) Core body temperature b) The presence or absence of sweating c) The presence of vomiting d) Altered mental status
4) Which one of the following is the most effective way to cool a victim under most conditions?
a) Cold water immersion b) Cold water evaporative cooling c) Ice packs to the axilla/groin d) Tepid water evaporative cooling
5) Acclimatization to a hot environment should take how long for the average adult?
a) 1-3 days b) 4-6 days c) 7-10 days d) 11-14 days
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