Heat Exposure and Reactions

DEFINITION

• Symptoms that follow exposure to high environmental temperatures or vigorous physical activity during hot weather
• Symptoms during heat waves
• Heat cramps, heat exhaustion and heatstroke are covered
• Prevention of heat exposure symptoms also discussed

Types of Heat Reactions

• There are 3 main reactions to hot environmental temperatures and heat waves:
• Heatstroke or Sunstroke: Symptoms include hot, flushed skin; high fever over 105° F (40.5° C) rectally; the absence of sweating (in 50%); confusion or coma; and shock. A rectal temperature is more accurate than an oral temperature in these disorders. Heat stroke is a life-threatening emergency with a high death rate if not treated promptly.
• Heat Exhaustion: Symptoms include pale skin; usually no fever but can temporarily be elevated between 100 - 102° F (37.8 - 39° C); profuse sweating; nausea, dizziness, fainting, or weakness. Most of the symptoms are caused by dehydration from sweating. Because a person can progress from heat exhaustion to heat stroke, all patients with severe symptoms (e.g., fainting) need to be examined immediately. Patients with mild symptoms (e.g., dizziness or fever) who do not respond to fluid replacement and rest also need to be seen.
• Heat Cramps: Severe muscle cramps in the legs (especially calf or thigh muscles) and abdomen are present. No fever. Tightness or spasms of the hands may occur.

Causes

• All 3 reactions are caused by exposure to high temperatures often with high humidity.
• Exercising or other vigorous activity/labor during hot weather can cause heat production to exceed heat loss.
• Poor hydration interferes with sweating and increases the risk of heat reactions.
• Infants are at added risk because they are less able to sweat with heat stress.
• So are children who are vacationing in a hot climate and who have not acclimatized. The first heat wave of the summer can cause similar problems. It takes 8 to 10 days for you to become used to high summer temperatures.
• Heat stroke (a breakdown in the temperature-regulating mechanism) usually follows exposure to a very high environmental temperature (e.g. trapped inside a hot car, steam tents, crib near a radiator or indoors during bad heat waves without air-conditioning). 

See More Appropriate Topic (instead of this one) If

• Age less than 3 months and fever, see FEVER
• Fever and NO prolonged exposure to high environmental temperatures, see FEVER

First Aid For Heatstroke Or Sunstroke

• Call EMS (911) immediately.
• Cool the child off as rapidly as possible while awaiting EMS arrival.
• Move him to a cool shady place or air-conditioned room.
• Sponge the entire body surface with cool water (as cool as tolerated without causing shivering).
• Fan the child to increase evaporation.
• Keep the feet elevated to counteract shock.
• If the child is awake, give as much cold water to drink as he or she can tolerate.
• Fever medicines are of no value for heat stroke.

First Aid For Heat Exhaustion

• Put the child in a cool place. Have him lie down with the feet elevated.
• Undress him (except for underwear) so the body surface can give off heat.
• Sponge the entire body surface continuously with cool water (as cool as tolerated without causing shivering). Fan the child to increase heat loss from evaporation.
• Give as much cold water to drink as the child can tolerate until he or she feels better.
• For severe symptoms, drive the child in to be seen.

WHEN TO CALL YOUR DOCTOR

HOME CARE ADVICE FOR HEAT EXPOSURE

1. Heat Cramps - Reassurance:
   • Heat cramps are the most common reaction to strenuous exercise and heat exposure. They are never serious. Sometimes, they can be a warning sign of impending heat exhaustion.
   • The cramps occur in the muscles that were working the hardest.
   • Heat cramps can be quite painful.
   • Heat cramps mean that the body needs rest and more liquids and salt.
2. Dizziness - Reassurance:
   • Dizziness and weakness are usually caused by mild dehydration from all the sweating that occurs with heat exposure.
   • Dizziness should clear in 1 to 2 hours after the lost fluids are replaced.
   • Mild dehydration can also cause nausea. It should pass after drinking adequate fluids.
3. Fever - Reassurance:
   • The body can normally become overheated from sun exposure and/or exercise. The temperature should come down to normal after lost fluids are replaced and your child has been able to rest for 1 or 2 hours.
   • NO MEDS: Fever medicines are of no value for this type of fever.
   • COOL BATH: After your child drinks some liquids, encourage a cool bath or shower for 5 minutes (Reason: brings down the temperature more quickly)
4. Drink Liquids to Rehydrate:
   • Give a sports-rehydration drink (e.g., Gatorade), which contains sugar and salt.
   • OR give water with some salty foods (e.g., potato chips or pretzels).
   • Start with 2 or 3 cups (480-720 ml) for teens.
   • Then give 1 cup (240 ml) every 15 minutes for the next 1-2 hours. (Teens)
   • The urine color can help tell if drinking enough liquids. Dark yellow urine suggests dehydration. Clear or light yellow urine suggests drinking enough liquids.
5. Food: After your child has taken 2 or 3 glasses of water, offer some salty foods (e.g., potato chips or pretzels). Don't give salt tablets (Reason: they slow down the absorption of water and may cause vomiting)
6. Rest: Rest in a cool place with a fan until feeling better.
7. Prevention Of Heat Reactions:
   • When your child is working or exercising in a hot environment, have him or her drink large amounts of cool water to prevent dehydration. For teens, this means at least 8 ounces (240 ml) every 15 minutes. Water is the ideal solution for replacing lost sweat. Very little salt is lost.
   • Special glucose-electrolyte solutions (sports drinks) offer no advantage over water unless exercising for longer than an hour. If that is the case, replace 1 water drink per hour with a sports drink.
   • Have your child take water breaks every 15 minutes in the shade. Encourage him to drink some water even if he's not thirsty. Thirst can be delayed until a person is almost dehydrated.
   • Avoid salt tablets, because they slow down stomach emptying and delay the absorption of fluids.
   • Have your child wear a single layer of lightweight clothing. Change it if it becomes wet with perspiration.
   • Physical activity in hot weather should be increased gradually.
   • Athletic coaches recommend that exercise sessions be shortened and less vigorous if the temperature exceeds 82°F (28°C), especially if the humidity is high.
   • Protect infants with fevers from heatstroke by not bundling them in blankets or excessive clothing. Children usually need the same number of layers of clothing as adults.
   • During heat waves, spend as much time as possible in cool environments with air-conditioning. Electric fans also help. Slow down. It takes at least a week to acclimate to a hot summer temperatures.
8. Prevention - Hot Tubs:
   • Age limit: Avoid hot tub exposure in children less than 3 years old.
   • Reason: Poor heat tolerance and risk for rapid onset of high body temperature.
   • When using a hot tub, limit exposure to 15 minutes and have a "buddy" system in case a heat reaction suddenly occurs.
   • Hot tubs and saunas should be avoided by people with a fever, or following vigorous exercise when the body needs to release heat.
9. Call Your Doctor If:
   • Vomiting interferes with taking fluids
   • Signs of dehydration occur
   • Muscle cramps last over 4 hours
   • Fainting occurs
   • Fever rises above 104°F (40.0°C)
   • Fever lasts over 2 hours
   • Your child becomes worse

Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Author and Senior Reviewer: Barton D. Schmitt, M.D.

Last Reviewed: 10/26/2011

Last Revised: 10/26/2011

Content Set: Pediatric HouseCalls Symptom Checker

Copyright 1994-2012 Barton D. Schmitt, M.D