Infants, children, and adolescents are at increased risk for heat-related illness due to their inability to remove themselves from dangerous environments. Evidence shows that morbidity and mortality from heat illness is related to the length of time core temperature is elevated, so rapid reduction and accurate serial measurements are crucial to prevention of organ system damage and death. The primary methods of patient cooling are conduction (ice-water immersion, cold packs) and convection (moisture and moving air). The choice of method used may depend on availability of equipment, but there is evidence that can guide optimal use of resources. This issue presents evidence-based recommendations and best practices in heat-illness resuscitation, including managing children who are obese, have special needs or take medications, and advocacy for prevention strategies.
On a hot summer day, an obese 15-year-old adolescent boy presents to the ED after a week of two-a-day football practices. He has completed 10 practices to date. He presents with headache, muscle aches, nausea, and 2 episodes of vomiting. The patient denies any trauma or injury. His past medical history includes ADHD, and his home medications include methylphenidate. His physical examination is remarkable for a fatigued-appearing obese boy with flushed, sweaty skin. The patient’s vital signs are: heart rate, 120 beats/min; respiratory rate, 24 breaths/min; blood pressure, 128/76 mm Hg; rectal temperature, 39°C (102.2°F); and oxygen saturation, 98% on room air. You begin to wonder how severe his heat-related illness is and whether diagnostic studies need to be ordered. What treatment needs to be initiated immediately, or can treatment wait while you see another patient?
While you are considering these questions, EMS brings in a lethargic 8-month-old infant. The paramedic reports that a bystander found the infant in a locked vehicle. The parents could not be located, and the amount of time the child was in the car is unknown. The physical examination demonstrates an obtunded infant with no evidence of sweating. The infant’s vital signs are: heart rate, 192 beats/min; respiratory rate, 20 breaths/min; blood pressure, 70/45 mm Hg; rectal temperature, 41°C (105.8°F); and oxygen saturation, 92% on room air. You consider whether this is heat exhaustion or a more severe case of heat stroke. You begin to think about the diagnostic studies that you will need to order to confirm the diagnosis and when you should begin treatment.
The following day, you are volunteering as a clinician on the medical team for a marathon. Bystanders bring over a 16-year-old adolescent girl with altered mental status. Her temperature is 40°C (104°F). She is responding to questions, but is confused to place and time. You decide to contact EMS for transport to the ED and plan to initiate cooling measures. While waiting for EMS to arrive, you look around to see what resources are available and consider what cooling measure would be most effective.
Heat-related illness is the result of inadequate thermoregulation during excessive heat exposure and/or exertion.1 Heat-related illness varies in clinical presentation depending on the severity of illness, which ranges from mild heat stress to life-threatening heat stroke. The variability in presentation requires emergency clinicians to include this diagnosis in their differential for any patient who presents with hyperthermia.
Heat-related illness does not occur only in summer months or in hot climate regions. Zeller et al found that while most exertional heat-related illness in the United States does occur during the hotter months of May to September, a few occurred during the winter months.2 Local and federal health services record fatal and nonfatal heat illness incidents, noting correlations to weather conditions.3,4 From 1997 to 2006, 54,983 patients were treated for exertional heat-related illness in emergency departments (EDs) in the United States, with a 133% increase in that time frame. Pediatric patients aged < 19 years accounted for the largest proportion of heat-related illness, at 47%.5 Heat stroke has the highest mortality of all heat-related illnesses, with a mortality rate ranging from 6.4% to 33%.1,2 To reduce morbidity and mortality in patients with heat illness, it is essential that emergency clinicians recognize heat-related illness and implement resuscitation quickly. This issue of Pediatric Emergency Medicine Practice provides an overview of heat-related illness and offers recommendations for prevention and management in the pediatric population.
A systematic literature search was performed in PubMed for articles on heat-related illness in patients aged 0 to 18 years, with limitations to articles published in English from 1996 to 2017. The following search terms were used: exertional heat illness, heat stress, heat cramp(s), heat exhaustion, and heat stroke. A total of 121 articles were selected as being relevant to this issue, including case reports, epidemiological studies, clinical reviews, retrospective and prospective observational studies, canine experimental studies, simulation studies, and a few small randomized controlled studies.
1. “The outside temperature was only 26.7°C (80°F). There’s no way that the baby’s elevated temperature was related to being left in the car.”
Even in mild-to-moderate environmental temperatures, the temperature inside a car can reach dangerous levels. McLaren showed environmental temperature ranges of 22.2°C to 35.6°C (72°F-96°F) can increase the internal car temperature to 47.2°C (117°F).18
2. “The patient’s rectal temperature was not high enough for her to be considered to have a heat-related illness.”
The diagnosis of heat exhaustion includes temperatures < 40°C (104°F). When considering the diagnosis of a heat-related illness, history of signs and symptoms and examination findings are important in diagnosis and initiating management.
3. “The boy’s axillary temperature was only 39°C (102.2°F), so heat stroke could not be a possible diagnosis.”
Only core temperature measurements utilizing rectal or esophageal probes should be used for diagnosis and management of a patient with a heat-related illness, as other external temperature measurements are inaccurate and often underestimate core temperature.
4. “It was only 26.1°C (79°F) with 80% humidity outside, so I didn’t consider a heat-related illness as a source of hyperthermia.”
The body’s ability to dissipate heat is related to both environmental temperature and humidity. When the humidity level reaches or exceeds 75%, heat loss by evaporation begins to decrease and the risk of heat-related illness during exertion increases.
5. “I didn’t stress preseason acclimatization conditioning to the patient’s football coach, as the temperatures do not exceed 32.2°C (90°F) in our area.”
Exertional heat illness among football athletes is 11 times more likely than in athletes in all other sports combined. Most heat-related illness occurs during the preseason, when athletes are unconditioned and it is the hottest time of the year. Humidity as well as temperature should be considered as risks for heat-related illness. It is therefore important that athletes are acclimated prior to full participation in preseason practice.
6. “Near the end of the championship game, the football player was experiencing nausea and fatigue. His oral temperature was 38°C (100.4°F). Since this was an important game and his temperature was not too high, we rehydrated him and allowed him to return to the game.”
When treating an athlete with heat exhaustion, in addition to rehydration, it is imperative to remove football equipment and place the patient in a shaded area to prevent progression to heat stroke.
7. “The patient had a temperature of 41°C (105.8°F) in the ED after football practice, so I asked the nurse to initiate cooling measures by placing ice packs on his body and turning fans on him.”
Evaporative cooling has been shown to be more effective than cooling with ice packs. Evaporative cooling is accomplished by spraying warm water over the skin with forced continuous airflow. Warm forced air or warm water is crucial for the evaporative process in order to maintain good peripheral perfusion and to minimize vasoconstriction.
8. “I ordered a dose of dantrolene prior to initiating cooling measures, as the patient’s temperature was 40.5°C (105°F).”
Although dantrolene is standard therapy for medication-induced malignant hyperthermia, there is no convincing evidence for the use of dantrolene in the management of exertional heat stroke. Initial management should be focused on rapid cooling measures.
9. “The patient is an offensive linemen. Since they don’t run as much as other football athletes, I thought he was less at risk for heat stroke.”
Athletes with a high body mass index are at increased risk for exercise-induced heat-related illness, due to their increased heat production, increased insulation, and decreased sweating rate, which prevents evaporative heat dissipation.
10. “I initiated rapid cooling measures in my patient whom I suspected had heat stroke. I instructed the nurse to stop once the patient’s core body temperature dropped below 37°C (98.6°F).”
To avoid hypothermia, it is recommended that cooling measures be stopped when the core temperature drops below 38°C to 39°C (100.4°F-102.2°F).
Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.
To help the reader judge the strength of each reference, pertinent information about the study, such as the type of study and the number of patients in the study is included in bold type following the references, where available. The most informative references cited in this paper, as determined by the authors, are noted by an asterisk (*) next to the number of the reference.
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Roberta J. Dunn, MD; Tommy Y. Kim, MD
August 2, 2017
September 1, 2020
Physician CME Information
Date of Original Release: August 1, 2017. Date of most recent review: July 15, 2017. Termination date: August 1, 2020.
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