Outbreaks, Alerts and Hot Topics

Heat-Related Illness in Children

Author: Kelly Sinclair, MD | Pediatric Emergency Medicine | Associate Professor of Pediatrics, UMKC School of Medicine | Clinical Associate Professor of Pediatrics, University of Kansas School of Medicine

Column Editor: Angela Myers, MD, MPH | Director, Division of Infectious Diseases | Professor of Pediatrics, UMKC School of Medicine | Medical Editor, The Link Newsletter

During summer months, heat-related illness in children is a significant medical concern. In 2021, 23 deaths from heat stroke in children left in a hot car were reported. While heat stroke is the extreme of heat-related illnesses, many other medical conditions are seen in hot and humid environments. The body temperature in children when outside in the heat may rise three to five times faster when compared to an adult. Here in the Midwest, humidity is a significant factor and increases the risk of heat-related illness.

Heat-related illness is caused by the outdoor temperature, the inability of a person to dissipate heat, or both.¹ Children rely primarily on evaporation to disperse heat and cool down when it is hot outside. Once the relative humidity is over 75%, evaporation is much less effective as sweat on the skin no longer functions to cool a child off. Children have a larger surface area-to-mass ratio, allowing more absorption of heat from the environment. Along with their higher metabolic rate and lower blood volumes when compared to adults, children are at increased risk in these hot and humid summer months.²

Heat-related illness comes in many forms. Miliaria rubra, or prickly heat, is most common in infants and young children.¹ Obstruction of sweat ducts in the skin leads to a raised, erythematous rash that is oftentimes itchy. Loose clothing and limiting skin emollients or lotions may prevent heat rash. Treatment is not necessary as it resolves spontaneously, but often symptomatic care for the pruritis makes children more comfortable.

Heat edema, although more common in the elderly, is seen in children. This edema presents as swelling in the lower extremities due to vasodilation and venostasis. Moving to a cooler environment and elevating the legs will help resolve the edema.

Heat cramps may be associated with an increase in body temperature (>38 C but <40 C). Cramping typically occurs in large muscle groups – legs, arms and, less frequently, abdomen. Cramping is seen after moderate to intense exercise in a hot environment and felt to be due to sodium depletion from sweating.³ Drinking sodium-containing products, such as sports drinks, and stretching in addition to moving to a cooler environment help treat the cramping.

Heat syncope is seen with a normal core temperature along with dizziness and orthostatic hypotension. Heat syncope is seen more often in the poorly acclimatized, elderly or chronically ill. Staying out of the heat, drinking lots of fluids and lying supine will make patients feel better and improve symptoms within about 30 minutes.

Heat exhaustion is due to water and/or salt depletion. Body temperature is elevated, but <40 C. Tachycardia, nausea, vomiting, syncope, dizziness and confusion accompany mild to moderate dehydration.^2,4 Confusion is mild and resolves quickly when the patient is in a cool environment and given liquids to rehydrate. Heat exhaustion may progress to heat stroke, so patients should be observed. If vital signs and confusion do not resolve, patients should be seen in an emergency department.

When temperatures and humidity are high outside, it is best to take precautions to ensure safety. Activities should be restricted based on heat index and age. Staying in the shade or in an air-conditioned environment is helpful. Drinking salt-containing fluids, water and sports drinks prevents dehydration. Loose, wicking and light-colored clothing is helpful. Acclimatizing to hot and humid environments is also important and may take as long as 14 days in younger children.³ Patients with heat-related symptoms that are unresolved in 30 minutes or worsening should seek emergency care.

References:

1. Xu Z, Etzel RA, Su H, Huang C, Guo Y, Tong S. Impact of ambient temperature on children’s health: a systematic review. Environ Res. 2012;117:120-131.
2. Lipman GS, Gaudio FG, Eifling KP, Ellis MA, Otten EM, Grissom CK. Wilderness Medical Society clinical practice guidelines for the prevention and treatment of heat illness: 2019 update. Wilderness Environ Med. 2019;30(4S):S33-S46.
3. Council on Sports Medicine and Fitness and Council on School Health, Bergeron MF, Devore C, et al. Policy statement—climatic heat stress and exercising children and adolescents. Pediatrics. 2011;128:e741-e747.
4. Jardine DS. Heat illness and heat stroke. Pediatr Rev. 2007;28(7):249-258.