The mercury on the outside thermometer is inching past 40oC for the third day in a row and for once you are grateful to be in the cool, air-conditioned emergency department. The emergency phone snaps you back into alertness. The paramedics are bringing in a toddler that has been liberated from the back of a parked car.
- Despite widespread public information campaigns children are still left alone in cars every heatwave.
- Just 15 minutes unattended is enough to raise the cars temperature to lethal levels.
- Heat illness varies on a continuum from heat stress and cramps to heat exhaustion and then heat stroke.
- Heat stroke is a medical emergency and is characterized by neurological deterioration, anhydrosis and a core temperature above 40oC
During the recent heatwave in Melbourne, when the temperature topped 40 degrees for four days straight, Ambulance Victoria received 60 calls for children trapped in cars. Fortunately there were no fatalities. During the 1995-2002 period in the United States there were 171 entirely preventable fatalities.
Studies have suggested that on a hot day the temperature in a locked vehicle can rise as high as 51-67oC within 15 minutes. 75% of this rise occurs within the first five minutes of the door closing, so even short periods of leaving a child unattended can be dangerous. There is some evidence that leaving the window cracked can make a difference but all the data suggests that it has to be open at least 20 cm to make an appreciable difference.
Even though kids have a larger body surface area-to-mass ratio than adults, they have much less effective thermoregulation. They have a higher metabolic rate so are really little furnaces. Unfortunately they are less well able to regulate their cardiac output in response to heat stress and produce less sweat per apocrine gland compared to adults. Perhaps more importantly, unlike most adults, they cannot get out if they are left in the car seat on their own.
Words are important. What the lay public mean when they say heat stroke is very different from what the medical professional means.
Heat stress is what we all feel when the mercury rises – we’re grumpy, irritable, sweaty and often listless but not unwell. Core temperature is unaffected.
Heat exhaustion occurs as a result of salt and/or water depletion.It may be compounded by nausea, vomiting and excessive sweating. The core temperature may or may not be up altered.
Heat stroke is a medical emergency and typically classified as either exertional (think running a marathon on a hot day) or non-exertional (sitting in a hot car). As the core temperature rises above 40oC the patient often becomes more lethargic and delirious. Seizures, then coma, eventually ensue.
Heat is lost via radiation, conduction, evaporation and convection with these latter two being most amenable to change.
As with all potentially toxic exposures (to heat in this instance) removal from the source is vital. The child should be managed in a cool environment if possible and attention paid to their ABCs.
- Airway – they may require intubation if clinically indicated
- Breathing – if they need to be intubated then mechanical ventilation will need to be initiated
- Circulation – children suffering from heat stroke are often profoundly dehydrated with challenging IV access. Don’t hesitate to break out your favourite intraosseous device. As peripheral cooling is instituted more blood is returned to the central circulation increasing the risk of pulmonary oedema.
- Disability – seizures should be treated with benzodiazepines initially but you should check the UEC urgently and assess the sodium for hypo- or hypernatraemia depending on whether salt and water depletion or pure water depletion predominates.
- Exposure – having discovered a high core temperature then it is time to do something about it. Techniques can range from the simple – remove clothes, ice packs in the axillae and groins, cool fans, cold IV fluids to the Macgyver – creating a cooling tent. This can be done by soaking a sheet in cold water and draping it, suspended, over the patient with a fan to push air through it. The aim is to maximize heat loss via convection, conduction and evaporation.
There is no evidence that antipyretics lower the temperature in cases of heat related illness.
Disposition for the sick patient is straight forward. They need admission to HDU/ICU. But what should you do for the well appearing child?
There is no consensus as to how long a patient should be observed but common sense would dictate that if their temperature has normalized and they are rehydrated then they are fit enough to go home.
That is the million dollar question. Certainly, in Australia, Section 231 of the Children and Young Persons (Care and Protection) Act 1998 clearly states:-
A person who leaves any child or young person in the person’s care in a motor vehicle without proper supervision for such a period or in such circumstances that :
(a) the child or young person becomes or is likely to become emotionally distressed, or
(b) the child’s or young persons health becomes or is likely to become permanently or temporarily impaired is guilty of an offence.
Hasn’t the distraught parent been through enough? This excellent piece from the Washington Post, entitled Fatal Distraction eloquently puts a parents struggle into words.
Little Nelly is brought in, nearly naked and crying. Her rectal temperature is 38oC and she tolerates a delicious icy pole. Her mother is beside herself. You discuss the case with the local social services who agree to follow up.
McLaren C, Null J, Quinn J. Heat stress from enclosed vehicles: moderate ambient temperatures cause significant temperature rise in enclosed vehicles. Pediatrics. 2005 Jul;116(1):e109-12. PubMed PMID: 15995010
Grubenhoff, Joseph A., Kelley du Ford, and Genie E. Roosevelt. “Heat-related illness.” Clinical Pediatric Emergency Medicine 8.1 (2007): 59-64.
http://lifeinthefastlane.com/education/ccc/heat-stroke/ accessed 21st January 2014