Definition : Hypothermia

Hypothermia is a medical condition that occurs when an individual's core body temperature drops below 35°C. Symptoms vary depending on the severity of the hypothermia and may include impaired judgment, shivering, decreased intellectual function, drowsiness or coma. This condition can be life-threatening and requires urgent medical attention. Prevention includes avoiding prolonged exposure to the cold, wearing warm clothing and staying hydrated during outdoor activities in the winter.

Humans maintain a temperature generally above that of their environment by producing heat themselves (thermogenesis). He produces this heat by consuming energy obtained from his own metabolism. The so-called normal internal temperature is 37°C. Man has several thermoregulation systems to regulate this temperature, allowing the proper conduct of chemical and biological reactions necessary for life (homeostasis).

Hypothermia is caused by a loss of body heat. This can be due to:

• prolonged exposure to cold temperatures,
• Immersion in cold water,
• excessive sweating,
•  a metabolic disease that affects the body's ability to produce heat.

The most severe hypothermia was recorded at 12°C in a two-year-old boy who survived despite this. The resuscitation of a Swiss victim in a state of hypothermia, following a cardiac arrest of almost five hours, was observed.

Hypothermia occurs when the core temperature (body temperature) is below 35°C,

• From 37 to 35°C: this is called normothermia,
• 35 to 32.2°C: this is mild hypothermia.

The victim remains conscious, but with phases of amnesia (loss of memory), apathy (emotional indifference), or difficulty speaking (difficulty pronouncing). She has problems with judgment and adaptation to the situation.

There is the presence of cutaneous vasoconstriction accompanied by pale and cold skin, with the presence of shivering and horripilation (erection of the hair). Blood pressure and heart rate are elevated. Breathing is more rapid (tachypnea) but with a small thoracic amplitude.

Auscultation sometimes shows bronchospasm. Reflexes remain sharp. Urinary disorders can be observed: polyuria (abundant urination), dysuria (difficulty to urinate).

• From 32.2 to 28°C: this is moderate hypothermia;

There is a global slowing down of the psyche (decrease of the intellectual functions), with permanent disturbance of the higher functions and speech. The victim's condition ranges from obnubilation (central nervous system damage) to coma. Pupils are dilated and photo-motor reflex (pupil accommodation to light) is absent.

The skin is icy and cyanotic (bluish). Mottling may appear. There is no more shivering, but a muscular hypertonia (involuntary muscular contraction) with tremors (very fine localized shaking). Reflexes are diminished.

The heart rate is slowed down, the blood pressure is lowered or even impenetrable in the periphery. The respiratory rate is decreased. Bronchial congestion is abundant with a risk of inhalation of secretions.

The electrocardiogram shows a sinus bradycardia (normal but slowed rhythm). Rhythm disorders may appear such as atrial fibrillation.

• Less than 28° C: this is severe hypothermia.

The victim is in a coma. Below 28°C, there is a risk of cardiac arrest due to ventricular fibrillation. Below 25°C, the victim may be in apnea (absence of spontaneous breathing).

Below 20°C, the victim may be in a state of apparent death with a flat tracing on electroencephalography. This presentation does not allow resuscitation to be stopped. Survivals in this situation have been reported, especially in children. A forensic death by cardiorespiratory arrest and/or flat EEG (asystole) should be reported in normothermia, i.e., a person in hypothermia can only be considered dead after medical rewarming in a hospital setting.

Treatment of hypothermia involves rewarming the victim and stabilizing vital functions. It is important to remove wet clothing and cover the victim with warm blankets. It is also important to regularly monitor breathing, heart rate and blood pressure. If necessary, cardiac resuscitation may be required.

Hypothermia is a dangerous situation that can cause irreversible damage to vital functions. It is important to understand the causes and symptoms of hypothermia so that it can be prevented and treated effectively. If you suspect that you or someone you know has hypothermia, it is important to seek medical help immediately.