Hypothermia

Overview of hypothermia

Regulation of body temperature is essential for the existence and survival of human beings. Fluctuations in the normal body temperature may result from environmental and physiological factors. In either case, an adverse systemic response is generated in the body. “Hypothermia” is one such disorder which is more prevalent in extremely cold conditions. Inhabitants of the cold climatic zones are the primary vulnerable groups of the disease. New-borns are also susceptible to the disease in many cases.

It affects the metabolic system of the body adversely and can even cause death. In the last few years, hypothermia has contributed significantly towards the steadily increasing morbidity and mortality rates.

What is hypothermia?

Hypothermia is the medical condition in which the core body temperature drops below 35^oC due to the inability of the body to generate adequate heat to maintain normal physiological mechanisms.

It is basically a clinical condition where the patient’s body is at sub-normal temperature.

Disruption of the normal cerebral and muscular functions occurs in this condition. In hypothermic patients, the rate of heat loss is more than the rate of heat generation.

The body loses its capacity to restore its normal temperature and this leads to hypothermia. This disease occurs after an exposure to extreme cold conditions, certain medications or due to some pre-existing illnesses.

How does temperature regulation occur in the body?

Before proceeding to details it is important to know the following mechanisms of core temperature regulation within the body-

• Vasodilation: The blood vessels dilate in this condition. This increases the surface blood flow and the heat loss. A surface blood flow of 3000 ml/min occurs under maximum dilation condition.
• Vasoconstriction: The blood vessels constrict in this condition. This leads to a reduction in peripheral blood flow. This mechanism retains the body heat. Under maximum vasoconstriction, the rate of cutaneous blood flow drops to 30 ml/min.
• Perspiration: Loss of body heat occurs through evaporation in this case.
• Shivering: It is the process of heat generation through an increase in muscular chemical reactions. The surface heat production increases by about 500%.

What causes hypothermia?

Hypothermia occurs due to an abnormal drop in the core body temperature. The general precipitating factors are as follows-

• The absence of sufficient acclimatization (capacity of the body to adapt to changing temperatures in the environment)
• Wearing insufficient warm clothing in very cold conditions
• Exposure to a cold climate for a long time
• Wearing moist clothes
• Accidental exposure to a cold environment (Eg: Immersion in cold water after a boat accident)
• Power cut for a long time, that causes room heaters to stop functioning
• Excessive drug and alcohol abuse (causes vasodilation)
• Certain over-the-counter medications such as antidepressants, antipsychotics, and tranquilizers (Eg: Benzodiazepines) and beta-blockers
• Loss of adaptability to changing climates due to aging
• Cerebrovascular attacks
• Systemic problems such as brain tumors, spinal cord problems, and trauma
• Endocrinal problems such as Hypothyroidism, Hypoadrenalism, and Hypoglycaemia
• Severe renal, hepatic or cardiac problems
• Skin problems such as exfoliative dermatitis
• Poor diet (diet deficient in vitamins and essential micronutrients)
• Extreme fatigue and exhaustion
• Dehydration due to low intake of fluids

What are the symptoms of hypothermia?

Hypothermia usually manifests through some specific symptoms. These will be discussed in separate sections-

Early warning signs

• Feeling very cold
• Extreme shivering
• Appearance of goosebumps
• Clumsiness
• Loss of coordination
• Mild speech impairment (slurred speech)
• Numbness of hands and fingertips
• Aloofness
• Irrational and illogical behavior
• Cold, reddish and dry skin

Symptoms after drop in body temperature

• Cessation of shivering
• Low pulse rate (may be absent in some cases)
• Low respiratory rate
• Gradual loss of consciousness
• Bluish discoloration of the skin

At a body temperature of around 30^oC

The following symptoms are common when the body temperature drops to 30^oC-

• Unconsciousness
• Arrhythmia
• Cardiac arrest

What are the different stages of hypothermia?

Hypothermia typically progresses through the following stages-

• Stage I: Body temperature is normal at this stage. It ranges from 36^o-37^o. The patient does not show any visible symptom.
• Stage II: This stage marks the onset of mild hypothermia. The body temperature varies between 32-35^o The prominent symptoms are- bluish skin, extreme shivering, the appearance of goose-bumps, mumbled speech, memory problems, mental confusion.
• Stage III: Moderate hypothermia occurs with a body temperature of 28-32^o Shivering does not occur anymore. The patient experiences drowsiness and hallucinations.
• Stage IV: Here the body temperature drops below 28^o This is called severe hypothermia. The main characteristics are- cessation of cardiac and respiratory functions, fainting and abnormal stiffness.

What are the different types of hypothermia?

The classification of hypothermia depends on the rate of heat loss. These are as follows-

• Acute hypothermia: This is also known as “immersion hypothermia”. It occurs in accidental situations such as falling into water or snow avalanche wherein the person loses heat very quickly. Asphyxia (breathlessness) occurs in a few cases.
• Subacute hypothermia: Doctors call this condition “Exhaustion hypothermia”. It is common in people who go for mountaineering for long hours at a stretch. Presence of cold windy weather may aggravate the symptoms.
• Chronic hypothermia: This is a relatively long-lasting situation. It is more prevalent in elderly people who live in poor heating conditions and unhygienic environments. A patient who has recently suffered a congestive heart failure or stroke is more likely to develop chronic hypothermia.

What are the main diagnostic tests?

A few laboratory examinations are necessary for the diagnosis of the hypothermic patients. Here is a list of the tests-

• Blood test (to detect a drop in RBC count)
• Lung test (to check the functioning of the lungs)

What is the treatment?

• Getting the person to a warm atmosphere and gently removing damp clothes from his/her body. He/she should be exposed to warm temperature and not sudden hot temperature.
• It is important to warm the trunk of the body first and not the extremities as it can lead to shock.
• Refrain from rapid warming. Also, don’t apply direct heat to the body.
• Call for medical help and initiate CPR till the help arrives.
• Wrap the person’s head and neck and administer warm, non-alcoholic fluids.

 
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