47. The effect of heat on children in vehicles
As with adults, the effect of elevated temperature on infants and children can be devastating. Heat stress is the initial discomfort from environmental cause followed by heat exhaustion. Dehydration and elevation of body temperature develops along with a range of signs and symptoms including faintness and headache. The final life threatening progression of environmental hyperthermia is heat stroke.
Heat stroke is classified as the severe end of hyperthermia; it is diagnosed by a core temperature above 40°C with associated central nervous system dysfunction. Heat stroke is a true medical emergency that is often fatal if not properly and promptly treated. Common symptoms and signs of heat stroke include: high body temperature, the absence of sweating, with hot, red or flushed dry skin, rapid pulse, difficulty breathing, strange behaviour, hallucinations, confusion, agitation, disorientation, seizures, decreased consciousness or coma which proceeds rapidly to multi-organ failure and death (Bouchama and Knochel 2002; Hoffman 2004; Shibolet et al 1976).
Small children and infants are more sensitive to extreme heat; they have a greater body surface area-to-mass ratio than adults, allowing them to absorb heat from the environment more quickly. They have less effective thermoregulation ability compared to adults. In children the ability to cope with high ambient temperatures is further compromised due to immature sweating mechanisms (McLaren C, Null J, Quinn J, 2005). Sweating progressively loses its cooling efficiency with rises in temperature anyway (Gibbs and Lawrence 1995).
Young children are more sensitive to heat than older children or adults as their body temperature can rise 3 to 5 times faster (Null 2011). This puts them at greater risk of heat stroke as their body temperature reaches dangerous levels much sooner (Kidsafe, 2009). Children can lose as much as 8% body fluid from dehydration in four hours where ambient temperature exceeds 50°C ensuring heat stroke occurs (King et al 1981). Kidsafe Victoria state that leaving children unattended in a car on any day is dangerous let alone a hot summer’s day. It could result in serious injury or death (Kidsafe, 2009). Though this form of injury is comparatively uncommon compared to others it is rising (Booth et al 2010).
The cause of heat stoke can vary with age. Adults are frequently affected by over exertion or as a result of the effect of medications being taken. Infant cause is usually due to environmental temperature or poor fluid intake even if the child is in good health (Wadlington et al 1976; Gibbs et al 1995; Whitehead et al 1996). Heat stroke is a comparatively uncommon event in children and usually related to vehicles or over warmed in bed (Krous et al 2001).
Children left in vehicles have further increased risk of burns from metal within cars or from possible abduction (McLaren C, Null J, Quinn J, 2005). The shortwave energy from the sun has little effect on the car window but has dramatic effect on objects within such as dashboards. This object heating then not only poses as a burn risk but also transmits radiation heat energy back into the vehicle (Null, 2012)
According to Kidsafe Victoria the RACV was called out to rescue 1,543 children locked in cars from November 2008 to October 2009 (Kidsafe, 2009). They do not provide the breakdown for how many of these were for unattended children.
Heat effects within vehicles
On a typical Australian summer day, the temperature inside a parked car can be 30°C to 40°C hotter than the outside temperature. 75% of the temperature increase occurs within the first 5 minutes and large cars heat up just as fast as small ones (Kidsafe, 2009). It has been demonstrated that a rise in ambient air temperature in a car can rise from 36ºC to 67ºC within 15 minutes (King et al 1981) and 34°C to 52°C in 20 minutes (Gibb and Lawrence 1995).
Similarly studies have demonstrated rises in temperature from lower starting ambient temperatures of between 23 ºC and 35 ºC can produce rises in vehicle temperatures of 12 ºC in the first ten minutes to 60 ºC in 30 minutes (Null 2012). Lethal temperature rises can occur in comparatively short times at temperatures of as little as 26°C. The rapidity of temperature rise will be more pronounced if the child is left in direct exposure to the sun (McLaren et al 2005).
Weather can vary dramatically including cloudy and overcast. This has been shown to lessen the impact on temperature rises within vehicles though in summer weather the vehicle temperatures will still be too severe for children (Grundstein et al 2009). The dramatic rises in car temperatures has been likened to the greenhouse effect due to windows allowing the entry of solar radiation but trapping within the radiation from warmed objects within (Grundstein et al 2010).
Though light coloured cars and sedans faired slightly lower, all measurements were significantly unacceptable for a child to be left in. To come close to acceptable temperatures windows had to be left more than half open but even this would result in severe dehydration of infants and subsequent heat stroke.
Even on comparatively cooler summer days rapid temperature rises to unacceptable levels with rises from 23°C to 48°C occurring within one hour (McLaren et al 2005). One reason cited regularly in a United States study was a reluctance of parents to disturb a child who was sleeping (Guard and Gallagher 2005). The same study also highlighted that a common reason for leaving children in cars was to use the vehicle as means of securing the child to allow the adult to sleep or perform some other activity. Tragically, over half of the cases were by adults who had simply forgotten the child was in the vehicle.
Grundstein et al reviewed published literature available and quantified the air temperature rises demonstrable in vehicles comparing actual vehicle air temperature over time intervals.
Having the windows down slightly has little effect on the inside car temperature McLaren et al 2005; Gibbs and Lawrence 1995; Roberts and Roberts 1976). Recent tests conducted by RACQ have shown that when car windows are left open by 10cm the inside car temperature is only 5°C cooler than with the windows closed (Kidsafe, 2009).
Statistics from the San Francisco State University show that the total number of U.S hyperthermia deaths of children left in cars from 1998 to 2012 is 539, an average of 38 per year. The overwhelming majority of these deaths are in the less than 5 year old group with a major emphasis in the less than two year old group (Null J, 2011). Statistics for Victoria are currently unavailable.
Children are at great risk of heat stress and environmental hyperthermia when left unattended in vehicles. This risk is not greatly reduced by cooler summer days or by leaving windows partly open. Ambient air temperatures in the mid twenty degrees Celsius can cause serious risk to children. The risk of serious illness or death is apparent in periods as short as 15 minutes and increases considerably in children younger than 3 years of age. This is a well understood observation and should be much better appreciated by parents of young children. There is evidence that many in the community remain unaware of the seriousness of the hazard and that public education remains strongly recommended.
Pre-hospital management includes extricating the child as soon as possible and immediate cooling using fanning, mist spray and removal to a cooler environment. Dehydration may be a very real concern. This may be therapy initiated by appropriate paramedics or expeditious transfer to the nearest paediatric emergency facility.
Jeff Kenneally www.prehemt.com
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