Hypothermia: Everything You Need to Know

Hypothermia is a condition in which the body temperature drops abruptly and can lead to multiple complications. Fortunately, most of the damages are reversible if proper treatment is initiated in time.
Hypothermia: Everything You Need to Know

Last update: 01 June, 2023

Our body temperature is the result of a dynamic balance between internal regulatory mechanisms and environmental conditions. In this sense, local and systemic conditions can occur when exposed to conditions with extreme temperatures. One of these conditions is hypothermia, are you interested in learning more about it? Keep reading!

Hypothermia occurs when the body temperature falls below normal when in contact with a cold environment, or the result of a disease that impairs the ability to retain heat. Studies affirm that this phenomenon occurs when the core temperature is below 35 degrees Celsius (95 F), triggering the appearance of characteristic signs and symptoms.

Symptoms of hypothermia

Hypothermia causes many symptoms
When hypothermia progresses, it can cause very obvious symptoms such as loss of consciousness.

The clinical manifestations of hypothermia usually appear progressively or suddenly, depending on the cause and severity of the condition.

Chills are usually the first symptom to appear; they appear due to the activation of peripheral mechanisms that seek to raise and recover body temperature. Similarly, it’s common to experience the following symptoms:

  • Pale and cold skin
  • Cyanosis
  • Shallow breathing
  • Difficulty moving or lack of coordination
  • Low heart rate
  • Numbness of the fingers and limbs
  • Confusion and drowsiness

In general, people with hypothermia tend to experience a slowdown in thinking, so they aren’t too aware of their state of health. In this way, people can become unconscious or suffer a cardiac arrest, shock, or even go into a coma when they don’t receive prompt medical attention.

Types of hypothermia

Hypothermia can be classified according to the origin of the triggering cause and based on the temperature of the affected person.

In this sense, we speak of accidental primary hypothermia when the reduction in body temperature is the result of environmental exposure to extreme cold. Secondary accidental hypothermia occurs as a result of an underlying disease or condition.

Similarly, some research suggests that hypothermia can be classified into 5 grades based on clinical signs and their relationship to core temperature. The existing degrees of hypothermia are based on the criteria of different specialized associations in the treatment of the condition, so it’s possible to classify it as follows:

  • Grade I (35 to 32 degrees Celsius / 95 to 90 Fahrenheit): The affected person is conscious, shaky, with dysarthria and an increased heart rate. At this point, all symptoms are reversible with rewarming treatment.
  • Grade II (32 to 28 degrees Celsius / 90 to 82 Fahrenheit): The patient is usually confused and sleepy but without tremors. Cardiac conduction disturbances also occur that can trigger fatal arrhythmias.
  • Grade III (28 to 24 degrees Celsius / 82 to 75 Fahrenheit): This occurs when the body’s thermoregulatory mechanisms fail. The person may become unconscious with vital signs present.
  • Grade IV (24 to 13.7 degrees Celsius / 75 to 57 Fahrenheit): Asystole occurs, so there’ll be an absence of vital signs and apparent death. At this point, resuscitation of the affected person is still possible.
  • Grade V (less than 13 degrees Celsius / 55 Fahrenheit): Known as irreversible hypothermia, and this means certain death.

Why does hypothermia occur?

The temperature of the human body is determined by an active balance between the production and removal of heat.

In this way, the hypothalamic thermoregulatory center, in conjunction with various peripheral mechanisms, seeks to maintain an optimal body temperature of 37.5 degrees Celsius (99.5 F) through perspiration, vasodilation, and muscle movement.

Hypothermia usually occurs due to excessive heat loss or insufficient heat production. In addition, the alteration of the central regulatory center can also be responsible for this condition.

In general, environmental exposure to low-temperature conditions is the main cause of hypothermia, as in the case of immersion in cold water.

On the other hand, some drugs such as ethanol and barbiturates can accelerate the loss of heat to the external environment. Some research has shown that up to 20% of patients experience unintended perioperative hypothermia while under the effect of anesthesia.

Most enzymatic processes in the human body release heat secondary to energy formation, usually in the form of ATP. In this way, the reduction of the metabolites necessary for the production of this molecule favors the appearance of hypothermia. Therefore, this phenomenon is common in people suffering from severe malnutrition, hypoglycemia, or marasmus.

Alterations in the central nervous system such as ischemia and trauma are also associated with hypothermia, which appears due to damage to the neurological pathways responsible for thermogenesis. Also, people with hypopituitarism, adrenal insufficiency, and hypothyroidism are at higher risk of developing this condition.


Hypothermia usually requires hospitalization
Many cases of hypothermia usually require hospital admission, for at least a few hours.

The diagnosis of hypothermia is based on the detection of body temperature and its association with the patient’s symptoms. In this sense, an oral, rectal, or tympanic thermometer is usually used to perform the reading. The detection of temperature below 35 degrees Celsius (95 F) will confirm the hypothermic state.

Values below 36 degrees Celsius (97 F) also allow for preventive measures. The treating physician will make a link between the clinical manifestations and the thermometer reading to classify hypothermia as mild, moderate, or severe.

The medical approach usually involves a comprehensive physical examination as well as a detailed check on the patient’s medical history. In this way, the doctor will identify the triggering situation for this condition and its possible relationship with a basic pathology, an environmental phenomenon, or drug poisoning.


Treating hypothermia is aimed at solving and slowing down the evolution of the triggering event. In this way, the initial treatment is to take the person out of the cold and use first aid measures, which will seek to warm the body progressively.

It’s important to remove the wet clothing in the event the person has been in water, and then protect the body with dry coats, and move the affected person to a warm place. In severe cases, immediate assistance by the emergency team and the use of cardiopulmonary resuscitation (CPR) protocols is necessary.

After releasing the patient from a critical condition, medical treatment aimed at rewarming and recovering normal body temperature will begin. Among the procedures used are the following:

  • Passive external rewarming (PER): This is used in people with mild hypothermia and consists of placing the person in a warm environment, with isolation, gradually raising the core body temperature.
  • Active Core Reheating (ACR): This is used in moderate to severe cases and involves various ways of raising the temperature directly and safely. In this sense, you can introduce warm and humidified air, irrigate the abdomen, administer warm fluids intravenously, or use diathermy methods and blood rewarming by hemodialysis.

Hypothermia prevention

The prevention measures of the hypothermic state are oriented to avoid the loss of heat through the skin. For this, it’s advisable to follow the following tips:

  • Avoid staying for a long time in spaces at low temperatures.
  • Don’t bathe or carry out water activities in rivers, lakes, or ponds during the winter
  • Employ protective measures and body isolation in cold environments
  • Consume warm or hot drinks

A condition that shouldn’t be underestimated

In most cases, hypothermia can be an unrecognized condition and of little concern to some people. However, changes in body temperature can trigger multiple cardiovascular, respiratory and neurological complications. In addition, severe hypothermic events can quickly lead to the death of the affected person.

For this reason, feel free to seek immediate attention for tremors, muscle spasms, pale skin, shallow breathing, confusion, and drowsiness. Specialist doctors are trained to identify your condition and guide you in recovering from your health.

  • Avellanas M, Ricart A, Botella J, Mengelle F et al . Manejo de la hipotermia accidental severa. Med. Intensiva. 2012; 36(3): 200-212.
  • Campos Chacón N. Hipotermia: a propósito de un caso. Med. leg. Costa Rica. 2016; 33(2): 159-164.
  • Hart SR, Bordes B, Hart J, Corsino D, Harmon D. Unintended perioperative hypothermia. Ochsner J. 2011;11(3):259-70.
  • Brandt S, Mühlsteff J, Imhoff M. Diagnosis, prevention and treatment of accidental and perioperative hypothermia. Biomedizinische Technik/Biomedical Engineering. 2012;57(5).
  • Avellanas Chavala M, Ayala Gallardo M, Soteras Martínez Í, Subirats Bayego E. Management of accidental hypothermia: A narrative review. Med Intensiva (Engl Ed). 2019;43(9):556-568.
  • García Iriarte A, Sáenz Mendía R, Marín Fernández B. La hipotermia [Hypothermia]. Rev Enferm. 2010;33(1):55-62.

Este texto se ofrece únicamente con propósitos informativos y no reemplaza la consulta con un profesional. Ante dudas, consulta a tu especialista.