Beat the Heat

CME CREDIT NOW AVAILABLE-1.0

AMA PRA Category 1 Credit FOR EACH ISSUE (2 ARTICLES)!!!!!!

 

 

By Thuy Bui, MD

thuy.bui@pemaweb.com

CASE – Part 1:

You are volunteering at the SuperHero Sprint – CHOA’s summertime 5K race.  A 12-year-old male running in his first race is brought to the medical tent by his mother.  He is diaphoretic and vomiting.  What are you concerned about?

BACKGROUND:

All heat-related deaths and illnesses are preventable.  However, despite this fact, each year an average of 658 people die from extreme heat per the CDC’s Morbidity and Mortality Weekly Report.

In the United States alone, there were 8,081 heat-related deaths from 1999-2010 according to the Centers for Disease Control.  And more recently, according to the National Safety Council’s Injury Facts, 87 people died in the U.S. in 2017 from exposure to excessive heat.

Children, because of multiple factors including their lower sweat rate and higher metabolic heat production, account for approximately 4% of heat-related deaths.  In fact, heat stroke is the 3rdmost common cause of exercise-related mortality for U.S. high school athletes; and since 1998, 619 children have died in vehicles from heat-related issues in the U.S.

DEFINITION:

Heat-related illness is a condition resulting from exposure to extreme heat where the body’s thermoregulatory mechanism is disrupted and cannot properly cool, resulting in a rapid rise in body temperature.

During normal thermoregulation, the body loses heat through 4 mechanisms.

  • – Conduction (direct contact with cooler objects)
  • – Convection (cooler fluid/air passes over the skin)
  • – Radiation (transfer of heat to the environment via electromagnetic waves)
  • – Evaporation (transfer of heat via evaporation of sweat/saliva)

When ambient temperature is >35˚C, heat loss by radiation and convection ceases. When humidity is >75%, air is so saturated that sweat cannot evaporate.  Therefore, unless some other method of cooling is introduced, some degree of heat illness will ensue.  Taking into account the heat and humidity of Atlanta especially during the summer, it is imperative and potentially life-saving to become familiar with the signs and symptoms of heat-related illness and how best to intervene when it is recognized.

CASE – Part 2:

You immediately recognize that this child is exhibiting signs of a heat related illness.  He is given a salt-containing sports drink and moved to a corner of the medical tent where fans are blowing.  Fifteen minutes later when you go check on him, he is no longer diaphoretic but now seems confused and more lethargic.  What do you do?

 HEAT CRAMPS:

Heat-related illness exists on a continuum with 3 main subcategories which are:

  1. Head Cramps
  2. Head Exhaustion
  3. Heat Stroke

Heat cramps are usually benign.  They occur as a result of salt losses causing brief but potentially severe muscle contractions.  Thermoregulatory function remains intact, and the body’s temperature remains normal. No work up is necessary. Treatment is rest – preferably in a cool, shady area and the encouragement of cold fluids and salty foods.

HEAT EXHAUSTION:

This usually occurs when there is mild to moderate thermoregulatory dysfunction. High ambient temperatures and/or strenuous exercise are usually the trigger causing dehydration and salt depletion. Signs and symptoms can include headache, dizziness, nausea/vomiting, diaphoresis, tachycardia, mild confusion but relatively normal mental status, weakness and potentially syncope.  There can be a mild increase in body temperature but typically the temperature remains < 40˚C.

If mild, treatment is similar to the supportive care given for heat cramps. However, if symptoms are more severe, the patient may need intravenous hydration with saline containing fluids. Most symptoms should resolve after 2-3 hours of fluids and rest.  No active cooling is usually needed, but patients should rest (no strenuous activity) with increased oral fluid intake for the next 24-48 hours.

If heat exhaustion is unrecognized and left untreated, it may progress to frank heat stroke which can be fatal.

HEAT STROKE:

With heat stroke, thermoregulatory mechanisms become overwhelmed and fail. Heat stroke is rapidly progressive and can be fatal.  Patients present with extreme hyperthermia – body temperature >40˚C – and altered mental status.  Associated systemic inflammatory response often leads to end organ damage.

There are typically 2 subtypes of heat stroke – exertional and classic. Exertional heat stroke occurs in young athletes exercising in elevated temperatures with high humidity for prolonged periods.  This usually develops over a period of hours.  Classic heat stroke usually occurs in patients who are more susceptible to dehydration (less efficient thermoregulation at baseline) including infants, young children, and the elderly.  This typically is seen during heat waves and develops over a period of days.

A special subtype of heat stroke, however, has emerged and is becoming more prevalent.  With more than 70% of heat stroke deaths occurring in children less than 2 years of age, approximately 30% of these deaths occurred when a child entered a hot location and could not escape on his own – the classic example being an infant left in a vehicle.  Temperatures in motor vehicles can reach over 60˚C (140˚F) in only 40 minutes time.  Sadly, an average of 38 kids die every year in vehicles because they were forgotten and left in the heat.

Patients having heat strokes will present with severe hyperthermia and altered mental status including hallucinations or psychosis progressing to seizures and potentially coma.  These children often have hot, dry skin because their sweating mechanism has failed.  They will be tachycardic, tachypneic and hypotensive.  As end organ damage ensues, these patients will develop rhabdomyolysis, coagulopathies, pulmonary edema, and arrythmias – all of which often lead to death.

Management of heat stroke is aggressive support and active cooling.  Start with your ABCs to ensure an intact airway and appropropriate volume resuscitation.  Simultaneously, start passive cooling – move the patient to a cool area and remove excess clothing.  Early active cooling is also essential.  In the pre-hospital setting, this includes external cooling methods such as immersing the patient in ice water, spraying tepid water on the skin and using fans to help with evaporative cooling, and applying ice packs to the body including areas with large blood vessels (the axilla, groin and neck).

In the hospital setting, internal cooling may be needed. This includes cooled IV fluids and internal cold water lavages (gastric, bladder, rectal and potentially peritoneal and thoracic lavages). Evaluation in the hospital setting includes continuous core temperature and cardiorespiratory monitoring with labs to detect and treat reversible end organ damage.  It is recommended to stop active cooling once the body temperature reaches 38.5˚C to prevent shivering which is counterproductive as it generates internal body heat and to help avoid hypothermia which may induce arrythmias.

Prognosis for heat stroke is directly related to duration of hyperthermia. Mortality ranges from 10-70% – greatest if treatment is delayed for more than 2 hours.  Therefore early detection and intervention is crucial in preventing heat stroke related mortality.

CASE – Part 3:

 You astutely recognize that this child has progressed from heat exhaustion to heat stroke.  You immediately call 911 for transport to the emergency department. While awaiting EMS arrival, you remove the child’s excess clothing and immerse him in the medical tent’s tub of ice. You ask the volunteer EMT to place an IV and immediately give the child a normal saline bolus.  After transport arrives and upon the patient being loaded onto the ambulance, he is now more alert and taking some sips of his sports drink. The mother thanks you for taking such great care of her son.  You are relieved that he is now recovering due to your early recognition and management of potentially fatal heat stroke.  Strong work!

SUMMARY:

Heat-related illnesses are common but preventable.  As healthcare experts, we are trained to recognize and treat these illnesses.  However, a more important component of our job is to counsel our patients and families on strategies to prevent the development of heat-related illness.

Some recommendations include:

  • – Avoid being outdoor during the hottest hours of the day
  • – Schedule strenuous activities for cooler times of day
  • – Move practices indoor
  • – Ensure adequate water for activities < 1hr
  • – Consume fluids with glucose and electrolytes for activities >1 hr
  • – Wear light-weight, light-colored, loose fitting clothes
  • – Change clothes when they become sweat-saturated
  • – NEVER leave unattended children in cars for any period of time

These preventative measures, when paired with astute and early recognition of heat-related illness, can allow physicians in the ambulatory setting to avert much of the morbidity and mortality associated with extreme heat.

*********See below to complete CME*************

CME Link

2 thoughts on “Beat the Heat

  1. Hi, I was attempting to take the CME after reading the HIV and heat stroke articles. My MAC would not allow me to note several answers on the question about risk factors – click on all that apply. I couldn’t click, therefore I failed. Please advise. Thanks, Karen Melde, CPNP

    Like

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