22.3 Heat-induced illness
Introduction
In children, heat related illness is the second most common cause of non-traumatic death after heart disease.1 Children are particularly at risk because of the following:
Certain genetic disorders such as ectodermal dysplasia and Fabry’s disease also put children at risk of heat-related illness.3 In these conditions, there is an impaired ability to dissipate heat through sweating.
Causes of heat-related illness
Usually seen in setting of high ambient temperature and humidity. Examples are athletics, summertime sporting events and during heat waves. Young children left in cars are also particularly at risk. A review of 171 cases of heat related car deaths found that in approximately 25% of cases the child gained access to an unlocked vehicle and in 75% of cases, the child was left by an adult.4
Increased heat production
Clinical syndromes
The neonate/infant
Overheating is the most common cause in the neonate and infant. It is important to distinguish the healthy infant who is overheated from the febrile infant (Table 22.3.1).5
| Overheated infant | Febrile infant |
|---|---|
| High rectal temp | High rectal temperature |
| Warm hands and feet | Cool hands and feet |
| Pink skin | Pale skin |
| Extended posture | Lethargic |
| Healthy appearance | Looks unwell |
| Abdomen temperature > hand temperature by <2 degrees | Abdomen exceeds hand skin temperature by >3 degrees |
Mild overheating is usually not dangerous to infants though there may be some association with apnoeic episodes in premature babies.5 Hyperthermia from overheating, with sudden death,6 particularly in families with a history of malignant hyperthermia.
Babies with heat-related illness may present like any seriously ill infant. Hewson’s work has summarised this as A,B,C, fluids in and out approach.7
Heat cramps
Heat cramps occur in the setting of strenuous exercise in hot/humid conditions. A relative lack of body salt plays a part. Heat cramps can be very painful; however, most last for less than 1 minute. Abdominal muscle cramps have been known to simulate an acute abdomen.8
Heat exhaustion
Heat exhaustion in children presents as hyperpyrexia, vomiting, headache, lethargy and weakness with a normal mental state. The major problem is body water depletion; however, in some paediatric patients (e.g. cystic fibrosis where greater amounts of salt are lost in their sweat), heat exhaustion may occur predominantly due to salt depletion.8
Heat stroke
See Table 22.3.2 for comparison of signs and symptoms of heat-induced syndromes.
| Condition | Symptoms | Signs |
|---|---|---|
| Heat syncope | Dizziness, feeling faint, may have brief loss of consciousness | Pallor, sweating, moist and cool skin, normal body temperature |
| Heat cramps | Painful, brief muscle cramps during or after strenuous exercise | Spasm of affected muscle group, body temperature usually normal |
| Heat exhaustion | Vomiting, headache, lethargy, weakness, normal mental state | Signs of dehydration, tachycardia, orthostatic hypotension, core temperature <40°C |
| Heat stroke | Episode of loss of consciousness common, neurological symptoms, irritability, confusion | Core temperature >40.5°C, acute change in mental state, sweating often present if exertional heat stroke |
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