Hyperthermia
Hyperthermia in children is quite common, potentially occurring post-exercise, and environmentally, such as when inside enclosed cars.1 The number of hot tub thermal injuries is unknown. That said, at a temperature of 34°C, the only effective means of body cooling is through the evaporation of perspiration, and within a hot water environment there is no evaporative loss.2, 3 Since there is no effective biologic means of temperature reduction, hot water immersion poses a substantial potential physiologic risk for both children and adults. Children are more susceptible to hyperthermia for several important reasons. Children’s skin is thinner than adults, and their surface area to body mass is much higher.4During heating, children also have elevated skin temperatures when compared to adults, indicating higher levels of peripheral vasodilatation.4 This allows faster heat transport (but also faster heat return as in this case.) Children also have a lower total blood volume per body mass than adults, presenting decreased cooling opportunity and also a potential for decreased central and brain blood flow when blood is diverted from central circulation to the periphery.4 The combination of these two vulnerabilities means that children raise their core temperatures much faster than adults and thus face a faster and higher risk of hyperthermia, especially when the peripheral circulatory increase only serves to return heated blood into the circulation.5