In the United States an average of 38 children die each year due to hyperthermia after being left in a motor vehicle. In 2017, a total of 42 children died in such circumstances and all but two were age 3 years or younger.1 After official recommendations from the National Highway Transportation Service Administration (NHTSA) and the American Academy of Pediatrics indicated that the safest place for a baby or a child is in the backseat,2,3 cases of fatal vehicular hyperthermia were noted to have increased; prior to the mid-1990s there were less than 10 deaths per year. The NHTSA is now required to collect data on vehicular injuries and death sustained in non-crash, non-traffic situations of which heat injury from exposure to a closed passenger compartment makes up more than one-half.4 However, those systems may be limited by non-report and lack of data so others have collected cases through searches of newspapers, websites, and other media outlets.1,5 Heat-related death is just the tip of the iceberg; it is likely that several hundred children each year suffer non-fatal heat-related illness that can range from minor heat exhaustion to severe heatstroke.6 In a recent 25-year analysis using a variety of health and law enforcement data, there were 3,115 incidents of children unattended in hot vehicles, resulting in 729 deaths.7
Children are far more vulnerable to heat illness and injury than adults due to their physical and developmental immaturity. This includes greater surface area to body mass ratio, higher metabolic rate, less ability to dissipate heat via perspiration, and developmental immaturity necessitating reliance on adult caregivers.8
Most of the vehicular heat-related deaths in the US occur in the South and Southwest.1 Texas and Florida lead for most deaths on a state level.1 Although most of these deaths occur in the summer months,1 it is important to note that risk of heat illness or death is present even on days that may not be considered extremely hot, making it a year-round risk. Motor vehicles act as a kind of greenhouse, trapping heat even on days when the temperature is mild. When the outside temperature is 80°F, the inside of a car in sunlight will reach nearly 110°F in 20 minutes and is likely to be more than 120°F in 1 hour.9 Approximately 80% of the temperature risk occurs in the first 30 minutes and cracking the windows of the car slightly does not significantly alter the compartment heating process or affect the maximum temperature reached.9
Investigations into the circumstances of these tragic events reveal that the majority are due to caregiver distraction, fatigue, and forgetfulness and not intentional neglect. In a study of 700 vehicular hyperthermia deaths from 1998 to 2016, approximately one-half of children were left in a car by a parent, 28% gained access to an automobile and could not get out, and 17% were intentionally left in the vehicle.1 One-third of the children were left in the vehicle by a father and 28% by a mother.1 A typical scenario involves a rushed parent whose routine or route is changed from normal and the parent inadvertently leaves the baby in the car.5
Heat-related illness represents a continuum of clinical scenarios ranging from minor conditions such as heat exhaustion to life-threatening heatstroke. Infants respond to heat increase initially by sweating. As they cry and become restless, both fluid loss and body temperature are increased, and eventually perspiring fails (anhidrosis). Damage occurs when the normal thermoregulatory mechanisms (radiation and convection) are unable to keep pace with exposure to excessive heat. Body temperatures may climb above 40°C; at 41.7°C, direct toxicity to cells occurs, there is a release of inflammatory factors, and damage to the vascular endothelium happens.10 Models have demonstrated that infants cannot compensate for heat rise after 20 minutes and will suffer shock and heat stroke within 105 minutes with demise within 125 minutes.11
Children may have several symptoms depending on the severity of heat illness. On the less severe end of the spectrum is heat exhaustion with classic findings including mild dehydration, core temperatures of 38°C to 40°C, profuse sweating, thirst, nausea, vomiting, and feeling faint.8 Heatstroke, a severe form of heat illness presents with significant dehydration, core temperature of over 40°C, hot/dry skin, lack of perspiration, vertigo, confusion, ataxia, unconsciousness, seizures, and shock.8 Mortality for heat stroke is between 17% and 80%.12,13 Children with severe heat illness (heat stroke) may have a variety of electrolyte abnormalities including hyperkalemia or hypokalemia and hypernatremia or hyponatremia.8 Rhabdomyolysis, acute tubular necrosis, and coagulation disorders can occur in severely ill children.8
Along with stabilization of the child's airway, breathing, and circulation, the initial priority in the care of a child with heat-related illness is core body cooling. Active, aggressive cooling measures should be begun if the child is symptomatic with a body temperature of 38.9°C or greater. Such measures are conductive methods and they include removal of clothes and application of icepacks to the axilla and groin. Lukewarm mist can be directed over the child's skin and fans directed at patient or cooling blankets used. Hydration with cool intravenous (IV) saline should be initiated and facilitated by a commercial fluid cooler if available or by adding extra IV tubing and running the tubing through an ice bath.8 Iced gastric lavage is another method to accomplish core cooling; however, this method should only be used in a patient who is either intubated or effectively able to protect his or her airway. Continuous monitoring of rectal temperature is vital, with active cooling measure continued until the child's core body temperature is below 38.9°C. Careful monitoring of hydration status with rehydration is necessary as severe dehydration is common in these patients, although some have normal hydration status. Initial hydration with IV isotonic fluid is recommended. In severely ill children, a Foley catheter should be placed to accurately measure output. The process of aggressive cooling may result in shivering and if vigorous should be controlled as it results in enhanced heat production. This can be accomplished with benzodiazepine. Of note, antipyretics are not effective in treating elevated body temperature caused by overheating.
Vehicular hyperthermia is preventable and there are several interventions aimed at preventing its occurrence. As with many injury prevention approaches, they can be categorized using the classic “E's”: education, enforcement, and engineering.
Educational programs that strive to raise public awareness of the danger of vehicular hyperthermia emphasize the importance of never leaving a child alone in a motor vehicle and advocate for a habit of checking the back seat prior to leaving and locking the car. One such program's main message is to “Look before you lock.”14 Importantly, these programs stress that this can happen to any busy parent due to distraction, stress, and forgetfulness. Such programs also advise that parents should keep cars locked when not in use to prevent children from gaining access to the interior and that vehicles are inappropriate places for children to play or to nap. Additionally, parents and caregivers should be reminded to supervise young children more closely during changes in routine and times of family stress. Pediatricians should provide parents with tips about using reminding “devices” (items that are needed), such as placing a purse, work identification badge, or cellphone in the back seat.15 Another suggestion is to keep a doll in the car seat when it is not in use, and moving it to the front seat when the child is occupying the car seat.5
Enforcement of laws that make it illegal to leave a child in a car alone are now present in 19 states,5 but child advocates and injury prevention experts advise that such laws will not affect the distraction and forgetfulness that lead to most of the heat-related vehicular child deaths. A total of 15 states have Good Samaritan laws that protect people who act when they see a child left in a vehicle.5
Recognizing that education and laws will not be enough to prevent deaths, others have focused on engineering solutions that address the forgetfulness and distraction that cause parents to forget their children in cars. In July 2017, the HOT CARS (Helping Overcome Trauma for Children Alone in Rear Act) act was introduced in the US Senate and House of Representative, which, if passed, would require all new passenger motor vehicles to be equipped with a child safety system that would alert the driver about backseat passengers when the vehicle is turned off.16 Although this legislation has not been passed and enacted yet, some manufacturers have integrated sensors and alerts to warn the driver to look in the back seat in newer model cars.17 More recently a company has introduced a sensor that detects any motion in the passenger compartment, alerting a driver before locking the vehicle.18 These interventions are far more likely to be successful as they create methods that passively protect the child, without the need for conscious action on the part of the driver.
- Null J. Heatstroke deaths of children in vehicles. http://noheatstroke.org. Accessed February 28, 2018.
- National Highway Traffic Safety Administration. New age-focused guidelines help parents make more informed choices. https://www.nhtsa.gov/press-releases/nhtsa-releases-new-child-seat-guidelines. Accessed February 20, 2018.
- American Academy of Pediatrics. AAP updates recommendation on car seats. https://www.aap.org/en-us/about-the-aap/aap-press-room/pages/aap-updates-recommendation-on-car-seats.aspx. Accessed February 20, 2018.
- US Department of Transportation.National Highway Traffic Safety Administration. Not-in-traffic surveillance: non-crash fatalities and injuries. http://noheatstroke.org/NHTSA2015.pdf. Accessed February 20, 2018.
- Kids and Cars website. https://www.kidsandcars.org/resources/state-laws/. Accessed February 28, 2018.
- Centers for Disease Control and Prevention (CDC). Injuries and deaths among children left unattended in or around motor vehicles--United States, July 2000–June 2001. MMWR Morb Mortal Wkly Rep. 2002;51(26);570–572.
- Zonfrillo MR, Ramsay ML, Fennell JE, Andreasen A. Unintentional non-traffic injury and fatal events: threats to children in and around vehicles. Traffic Inj Prev. 2017;19(2):184–188. doi:10.1080/15389588.2017.1369053 [CrossRef]
- Lin J, Losey R, Prendergast HM. An evidence-based approach to hyperthermia and other heat-related emergencies. Pediatr Emerg Med Prac. 2009;6:1–14.
- McLaren C, Null J, Quinn J. Heat stress from enclosed vehicles: moderate ambient temperatures cause significant temperature risk in enclosed vehicles. Pediatrics. 2005;116:e109–e112. doi:. doi:10.1542/peds.2004-2368 [CrossRef]
- Aggarwal Y, Karan BM, Das BN, Sinha RK. Prediction of heat-illness symptoms with the predictions of human vascular response in hot environment under resting conditions. J Med Syst. 2008;32:167–176. doi:. doi:10.1007/s10916-007-9119-3 [CrossRef]
- Grundstein AJ, Duzinski SV, Dolinak D, Null J, Iyer SS. Evaluating infant core temperature response in a hot car using a heat balance model. Forensic Sci Med Pathol. 2015;11(1):13–19. doi:. doi:10.1007/s12024-014-9619-7 [CrossRef]
- Jardine DS. Heat illness and heatstroke. Pediatr Rev. 2007;28:249–258. doi:10.1542/pir.28-7-249 [CrossRef]
- Helman RS. Heat stroke. www.emedicine.com/med/topic956.htm. Accessed February 21, 2018.
- Where's Baby website. Look before you lock. www.wheresbaby.org. Accessed February 21, 2018.
- Guard A, Gallagher SS. Heat related deaths to young children in parked cars: an analysis of 171 fatalities in the United States, 1995–2002. Inj Prev. 2005;11:33–37. doi:10.1136/ip.2003.004044 [CrossRef]
- Kids and Cars website. Hot cars act of 2017. http://www.kidsandcars.org/hot-cars-act-of-2017/. Accessed February 21, 2018.
- Valdes-Dapena P. GM unveils new feature to prevent child deaths in hot cards. http://money.cnn.com/2016/06/13/autos/gmc-child-back-seat-reminder/index.html. Accessed February 21, 2018.
- Craft A. CES 2018: new sensor technology could prevent ‘hot car’ infant deaths. http://www.kidsandcars.org/2018/01/09/ces-2018-new-sensor-technology-could-prevent-hot-car-infant-deaths/. Accessed February 21, 2018.