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