Hypothermia

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Hypothermia is defined as a core body temperature lower than 95˚F. Primary hypothermia accounts for around 1000 to 1300 deaths each year in the United States. Among infants and children, the estimated death rate is between 0.2 and 1 per million, but there is uncertainty surrounding these estimates. This is because hypothermia goes undiagnosed in many cases.

Missed hypothermia is common and can be fatal. Recognition of hypothermia is crucial to preventing unnecessary deaths and managing the condition. Core temperature measurement is a critical element of diagnosing and treating hypothermia, which is why measurement should be taken as soon as possible.

This article contains everything parents and caregivers should know about hypothermia in children, as well as how to identify the different stages of hypothermia.

Stages of hypothermia

There are 3 different stages of hypothermia, which differ depending on core temperature. Recognition and treatment depend on the stage of the hypothermia.

1. Mild: A core temperature of 90˚ to 95˚F.
2. Moderate: A core temperature of 82˚ to 90˚F.
3. Severe: A core temperature of 82˚F.

A core temperature of 77˚ is sometimes referred to as ‘profound hypothermia’.

Symptoms of hypothermia

Mild: Typical signs of mild hypothermia include shivering, goosebumps, and pale or bluish skin. It is important to note that younger children and infants are limited in their ability to shiver and preserve body heat and may instead show rosy cheeks and a paradoxically healthy appearance.

Moderate: Moderate hypothermia is characterized by a decreased mental function which gives way to confusion, disorientation, clumsy movements, and slurred speech. Shivering stops and irrational behavior such as ‘paradoxical undressing’ occurs. As hypothermia progresses, heart rate, ventilation, and blood pressure become affected.

Severe: As hypothermia progresses to become severe, abnormally low heart rate and low blood pressure eventually give way to pulselessness or VT. Coma, dilated and fixed pupils, muscle rigidity, and flushed skin develop. These features, paired with a lack of shivering, can mean that the diagnosis for severe hypothermia is missed which leads to premature declarations of death.

How does the body respond to hypothermia?

The stage of hypothermia also affects the body’s response to the drop in temperature.

For example, in mild hypothermia, the body uses compensatory mechanisms such as shivering and increased metabolism to stimulate heat production. It also reduces heat loss through vasoconstriction, which is when the blood vessels tighten to prevent heat transfer from the body’s core into the environment.

However, during moderate hypothermia, these compensatory mechanisms start to fail. This can cause cardiorespiratory depression, meaning the lungs can no longer efficiently exchange carbon dioxide and oxygen. Moderate hypothermia can also lead to altered mentation, which can refer to memory loss, confusion, and disorientation.

In severe hypothermia, the basal metabolic rate drops to half of what it should be. Key bodily functions such as circulation and ventilation begin to shut down. Dilated and fixed pupils, coma, apnea (temporary absence of breathing), pulselessness, and muscle rigidity can all occur when the body’s core temperature continues to drop.

The body undergoes a number of physiologic changes during hypothermia, including:

• Respiratory depression: Breathing becomes slow, shallow, and irregular, before ceasing completely or temporarily (apnea).
• Hypovolemia: Decrease in blood volume.
• Circulatory collapse: Hypovolemia, in turn, causes reduced cardiac output, affecting the heart’s ability to contract and causing blood to ‘sludge’ or thicken. The heart rate thus becomes abnormally low which leads to circulatory collapse or failure.
• Arrhythmias: Hypothermia affects the heart’s ability to function correctly. This can cause cardiac arrhythmias (irregular heart rhythms) such as Ventricular Fibrillation (VF). VF is the most dangerous type of cardiac arrhythmia, causing the heart to quiver irregularly rather than pump blood around the body. VF can be caused by dramatic changes in body temperature.
• Other: Hypothermia can also cause abnormalities in the levels of sugar and potassium in the blood, as well as abnormally high acidity/alkalinity, abnormally low levels of platelets in the blood, and impaired blood coagulation.

Hypothermia in children

Children face a greater risk of hypothermia than adults, especially young infants. There are a number of different factors that can contribute to pediatric hypothermia:

• The younger a child is, the larger their ratio of surface area to body mass.
• Younger children cannot produce body heat by shivering.
• Children and infants have limited glycogen stores (body fuel reserves) meaning their heat production and maintenance are reduced compared to those of an adult.
• Children are often unable to recognize hypothermic exposure and are less capable of avoiding or escaping dangerously low temperatures.
• Children with underlying conditions may be predisposed to hypothermia, as are children with trauma or burns.
• Pediatric hypothermia does not require extremely cold conditions to develop and may go undiagnosed as a result.

Causes and common scenarios 

Hypothermia is caused by prolonged exposure to cold conditions. It can also be caused by serious illness, trauma, transport and resuscitation, child abuse involving exposure or cold water, and toxic exposure.
Common scenarios associated with hypothermia include:

• Children running away or becoming lost
• Children falling victim to cold water near-drowning.
• Children and adolescents getting involved in mountain accidents.
• Intoxicated adolescents becoming incapacitated outdoors, especially at night when temperatures drop.