Hypothermia

What is Hypothermia?

Hypothermia is a condition when your body temperature drops below 35 degrees Celsius or 95 degrees Fahrenheit. It’s more common in cold places and during the colder months, but it can also happen in milder climates. Hypothermia affects all parts of the body and the symptoms you experience would depend on how severe the condition is.

Your body temperature is controlled by a part of your brain called the hypothalamus. When it senses your body getting cold, it triggers specific responses like increasing muscle activity and your body’s basic metabolic rate (a measure of energy consumption at rest). This can double the heat your body produces. Shivering is another response your body uses to create heat and can speed up your metabolism 2 to 5 times the normal rate.

Newborn babies, however, can’t shiver because their nervous system isn’t fully developed. To make up for this, they have brown fat that generates heat. Brown fat produces a substance called thermogenin that disrupts certain processes in the cells to stop energy production and instead create heat.

Other bodily responses to the cold include the increase of certain hormones like thyroid, adrenal, and catecholamines. Your body can also manage blood flow to reduce heat loss. Other conscious efforts you make like wearing more clothes, finding shelter, starting a fire, or exercising can also help maintain or increase body heat.

Hypothermia is categorized as mild, moderate and severe based on the body’s core temperature. Mild hypothermia is when the body’s core temperature is between 32 and 35 degrees Celsius (90-95 degrees Fahrenheit). Moderate hypothermia is when it’s between 28 and 32 degrees Celcius (82-90 degrees Fahrenheit) and severe hypothermia is when it’s below 28 degrees Celsius (82 degrees Fahrenheit). These stages are important for rescue teams to know who might benefit from life-saving measures. As the severity of hypothermia increases, it can have greater negative effects on health, including death.

What Causes Hypothermia?

Hypothermia is a condition where your body loses heat faster than it can produce or absorb it. This can occur due to a number of reasons. Factors such as your nervous system and your reaction to cold help your body hold onto heat.

People who are very young or old, those with low blood sugar, malnourishment, or certain hormonal disorders can struggle to produce enough heat. Conditions like psoriasis, burns, or injuries to the nervous system can result in your body losing more heat. Issues like stroke, certain degenerative brain disorders, and drug abuse can interfere with your brain’s ability to regulate body temperature. Certain medications like general anaesthetics, beta-blockers, and certain types of painkillers and psychiatric drugs, as well as alcohol, can also lead to hypothermia.

Additionally, if someone can’t react properly to cold, they can end up with hypothermia. This often happens with individuals suffering from mental health disorders like dementia or substance abuse disorder. Sometimes, simply not having enough warm clothing or shelter can lead to hypothermia, which is unfortunately a common issue among the homeless population.

Risk Factors and Frequency for Hypothermia

Hypothermia leads to between 700 to 1500 deaths in the United States every year. It typically affects adults between 30 to 49 years of age. Men are ten times more likely to be affected by this condition than women. However, the exact number of people affected by hypothermia is not known. Even in hospitals, where care can be closely monitored, nearly half of the people with moderate to severe hypothermia do not survive.

• Every year, hypothermia causes 700 to 1500 deaths in the U.S.
• It mostly affects adults between 30 and 49 years of age.
• Men are ten times more likely to have hypothermia than women.
• The exact number of hypothermia cases is unknown.
• Almost half of the people with moderate to severe hypothermia do not survive, even with the best hospital care.

Signs and Symptoms of Hypothermia

Hypothermia, a dangerous drop in body temperature, can lead to a cardiorespiratory arrest. A quick check-up covering airway, breathing, circulation, disability, and exposure (ABCDE) can help identify patients in urgent need of resuscitative care. This is particularly crucial for those who are unconscious, not breathing, or have no pulse. Once the patient is stabilized or emergency conditions are ruled out, further investigations can be carried out.

People suffering from hypothermia are usually found to have a history of recent significant cold exposure. The symptoms they demonstrate depend on their core body temperature, which needs to be precisely measured for an accurate diagnosis and effective treatment. One reliable method for temperature measurement is using an epitympanic thermometer, which reflects the carotid artery temperature.

In mildly and moderately hypothermic, awake patients, rectal and bladder temperature readings may be used. However, in critical conditions and during rewarming, these methods may not work well because they tend to lag behind the true core temperature. Additionally, these methods may increase the patients’ exposure to cold in prehospital environments, thereby worsening their hypothermia. It’s also possible to measure esophageal temperature, but this is only advisable when the patient has an advanced airway in place.

Oral temperature readings are only useful to exclude the possibility of hypothermia, since most commercial thermometers can’t measure temperatures under 35 °C. Tympanic thermometers are also unreliable for the same reason. Regardless of the method used, it’s critical to obtain the core body temperature as soon as possible for effective management, even though this might be challenging in a prehospital setting.

• Mild hypothermia (32-35 °C/90-95 °F) may result in symptoms such as hunger, nausea, fatigue, shivering, pale-dry skin, increased body functions as the body tries to warm up, cognitive decline, memory impairment, poor judgement, problems with movement and speech, and increased urine production.
• Moderate hypothermia (28-32 °C/82-90 °F) may cause cognitive decline and lethargy, slow reflexes, and less responsive pupils, and may result in low blood pressure, slow heart rate, and slow breathing. Shivering typically stops when the body temperature reaches 30 to 32 °C and unusual behaviors such as removing clothing may occur. Heart rhythm disturbances may begin, the most common being atrial fibrillation.
• Severe hypothermia (less than 28 °C/82 °F) results in a drastic decline in cerebral blood flow leading to unconsciousness and a decrease in blood pressure, heart rate, and cardiac output. Heart rhythm disturbances may occur along with pulmonary congestion, decreased urine production, and absent reflexes. The condition can lead to cardiorespiratory failure.

Patients suspected of hypothermia should undergo a complete history and physical examination to rule out local cold-induced injuries, any traumatic history, or any underlying conditions. Certain vital signs and symptoms not typically associated with the observed degree of hypothermia may indicate other health issues such as hypothyroidism, adrenal insufficiency, sepsis, hypoglycemia, carbon monoxide poisoning, alcohol abuse, malnutrition, and accidental or intentional drug overdose. Certain medications, such as beta-blockers, clonidine, neuroleptics, meperidine, and general anesthetic agents, can also cause hypothermia.

Testing for Hypothermia

For anyone who may be in a harmful or dangerous state, the first thing doctors need to do is check the patient’s Airway, Breathing, and Circulation (this is known as the trauma ABCs). Once these vital functions have been evaluated, the doctor will remove the patient’s clothing to determine their injuries and cover the patient with warm, dry blankets to help them maintain body heat. They will then do some standard lab tests, which include a finger-stick glucose test to check blood sugar, a complete blood count to measure the number of blood cells, and a basic metabolic panel to assess the body’s metabolism.

Sometimes, increases in a patient’s hemoglobin and hematocrit (parts of the blood) can happen due to cold, which makes the body release water. Blood sugar levels can change without any particular pattern. However, in patients with diabetes, extremely low or high blood sugar levels can be caused. Additionally, every 4 hours, your doctor might have to reassess your electrolyte levels, which are minerals that help regulate the body’s fluid levels, during the treatment for severe cold exposure.

Before any invasive procedures (like surgery or injections), a panel to test blood clotting must be taken. However, for this test to be reliable, the patient’s actual body temperature must be 37 °C. There could also be a need to check the Fibrinogen, a protein involved in clotting, to rule out a dangerous condition called disseminated intravascular coagulation (where blood clots form throughout the body’s small blood vessels).

Your doctor may also order tests to check for lactate (a chemical that can indicate a lack of oxygen), creatinine kinase (an enzyme linked to muscle damage), troponin (a protein that can signal heart damage), thyroid-stimulating hormone (a hormone controlling metabolism), cortisol (a hormone that helps your body respond to stress), and other substances. Toxicology screens can identify any drugs or toxins that may be in your body.

Your doctor will use imaging exams based on your symptoms and condition. Some patients may have experienced an event like trauma or a stroke which caused their body temperature to drop significantly. X-rays can be normal if there wasn’t any trauma or underlying condition in the chest area. Doctors may use a bedside ultrasound to confirm heart activity and volume status. A head CT scan may benefit people who have changes in their mental state not matching the severity of their cold exposure, particularly if a head injury or stroke is suspected.

Electrocardiography (ECG, a test that measures electrical signal of the heart) is needed due to the common occurrence of irregular heart rhythms in patients with extreme cold temperatures. Cold can slow down the electrical pulses through the heart, which can cause long QT intervals, a heart rhythm disorder that can cause fast and chaotic heartbeats. A specific type of wave, known as an Osborn or J wave, which is associated with a specific change in this electrical activity, can also be observed. They can vary in size based on how cold the patient is.

Atrial fibrillation, a disorder that makes the heart beat very fast and irregularly, is also commonly occurring. Slow heart rate is more common in patients exposed to cold temperatures and it can increase the risk of ventricular arrhythmia, a life-threatening condition that causes the heart to beat irregularly.

Treatment Options for Hypothermia

If you’re suffering from hypothermia, it’s crucial to get warm quickly and prevent further loss of body heat. The first steps involve making sure your airway is clear, you can breathe easily, and your circulation is normal. It’s also essential to remove any wet clothing immediately and replace it with dry clothing or blankets to help retain heat.

Patients with moderate or severe hypothermia need to be handled gently because sudden movements can place stress on the heart and potentially cause a dangerous heart rhythm. It’s also important to check for related health conditions or injuries. Those who have low blood sugars might receive oral glucose.

The goal of hypothermia treatment is to warm your body back up using various methods. For mild hypothermia, the method often used is “passive external rewarming,” where additional insulating layers are placed on your body to help maintain your body heat and increase your temperature by 0.5 to 2 degrees Celsius per hour.

Another natural bodily function, shivering, can produce heat and help you get warm. However, it requires sufficient glucose or sugar stores in your body, and it can put a strain on your heart and lungs by increasing your usage of oxygen.

If your hypothermia is moderate to severe or isn’t responding to basic treatments, “active external rewarming” may be necessary. This method can involve using a heated air unit or warm pack on your body to boost your body temperature. However, care must be taken when using warm water immersion, such as immersing the hands and feet in warm water, as this can lead to a sudden increase in blood flow from your cold veins to your heart.

Sometimes, more invasive methods are required to reheat your body. Techniques can range from using warm mist through a humidifier or warm IV fluids, to washing warm saline in body cavities like your stomach, bladder, colon or chest. Some more extensive procedures, known as “pleural lavage” and “peritoneal lavage,” involve using warm fluids to wash out and warm up the chest cavity and the abdominal area. These procedures can help detect hidden internal injuries.

Lastly, the fastest rewarming methods involve circulating warm blood through major blood vessels or the heart. These methods are typically reserved for patients in cardiac arrest, unstable conditions, or if other warming methods aren’t working. These complex procedures can raise your body temperature by 7-10 degrees Celsius per hour while also improving oxygen flow and circulatory support. However, these procedures are not offered in all medical facilities and require blood-thinning medicines that may increase the risk of bleeding.

What else can Hypothermia be?

Unusually low body temperature can be a sign of many different health problems. Physicians may consider the following categories of conditions when trying to figure out the cause of a patient’s hypothermia:

• Central failure (problems with brain function), such as a stroke, brain trauma, or issues with the hypothalamus — a part of the brain that helps regulate body temperature
• Peripheral failure (problems with the nervous system outside of the brain and spinal cord), such as a severe spinal cord injury or nerve damage
• Endocrine problems (issues with the hormone-producing glands in the body), such as diabetic ketoacidosis, adrenal insufficiency, pituitary gland disorders, or lactic acid buildup in the body
• Lack of adequate energy, which could be due to low blood sugar or malnutrition
• Neuromuscular issues (problems with the nerves controlling muscle function), such as extreme inactivity due to young or old age, or impaired shivering
• Skin-related issues, such as burns

Another cause of hypothermia could be medicines and toxins or medical procedures. For example, childbirth, cold infusions (when a cold fluid is put into the body), or treatments for heat stroke could cause hypothermia.

Finally, the source of the hypothermia could also be linked to a variety of other conditions, including cancer spread through the body (carcinomatosis), heart or lung disease, serious infections, multiple injuries at once (multisystem trauma), or shock.

It’s crucial for doctors to thoroughly investigate all these possibilities in order to correctly determine what’s causing the hypothermia and how to treat it.

What to expect with Hypothermia

Severe hypothermia can be very dangerous and even deadly, although there are things that can make the outcomes better. For instance, if a patient is stable and suffers from primary hypothermia, they have almost a 100% chance of surviving and a full recovery of their brain functions if they receive rapid treatment with techniques to reheat the body.

Meanwhile, patients who experience a cardiac arrest and are treated with a procedure known as ECMO have about a 50% chance of survival. Patients could have better chances if they aren’t experiencing a lack of oxygen, injury from a traumatic event, or a severe underlying disease. It’s been observed that a full recovery of brain functions is possible even when the body temperature drops as low as 14°C due to accidental hypothermia.

In cases where patients with hypothermia experience a very fast, irregular heart rhythm called ventricular fibrillation, they are generally able to recover brain functions if they receive immediate resuscitation. However, if the heart doesn’t show any electrical activity, a condition known as asystole, the standard life-saving measures might not work. Those patients usually need to be rewarmed until their body temperature reaches 35°C before the heart rhythm is restored. In patients where asystole continues, the level of potassium in the blood is checked. If it is greater than 12 mEq/L, this may indicate irreversible damage to the tissue and cell death.

Generally, if patients are treated quickly, they are likely to have good outcomes, although they might have some remaining injury from freezing and muscle damage. Extremely old or young people and those with severe hypothermia generally have worse outcomes.

Possible Complications When Diagnosed with Hypothermia

Frostbite is an issue that can occur due to hypothermia, and it can lead to the loss of a limb if not treated quickly. It’s a type of condition called dry gangrene, but if it gets infected, it can turn into wet gangrene. A specific kind of infection involving bacteria called Clostridium perfringens can cause gas to build up under your skin, giving it a crackling sensation. If these frostbite infections don’t respond to medical treatment, it could lead to needing an amputation.

Hypothermia can also lead to other complications like:

• Increased urine production due to cold weather, known as cold diuresis
• Muscle injury, known as rhabdomyolysis
• Inhaling foreign materials into the lungs, known as aspiration
• Excess potassium in the bloodstream, called hyperkalemia
• Acute kidney injury
• Fluid buildup in the lungs, called pulmonary edema
• Loss of full control of bodily movements, known as ataxia
• Heart rate and rhythm problems, commonly atrial or ventricular fibrillation and pulseless electrical activity
• Coma
• Pancreatitis, or inflammation of the pancreas
• Death

Also, warming up too quickly after having hypothermia can also cause other complications, such as:

• Takotsubo cardiomyopathy, a type of heart disease
• Body-wide inflammation
• Electrical imbalances including an excess of potassium in the blood, too little phosphorus, magnesium, and calcium
• Infectious diseases like pneumonia
• Issues with platelets, which are critical for blood clotting
• Changes in blood sugar level from reduced glucose usage to insulin resistance

Quick identification and proper treatment can help to lessen the chances of these complications.

Preventing Hypothermia

Hypothermia, which is a dangerous drop in body temperature, can be prevented. Medical professionals can help by teaching patients ways to avoid this condition. One way is by adjusting behavior. This means trying to stay indoors when the weather is cold. If you have to go outside, then make sure to wear clothes that can protect you from the cold.

The second way is to look out for those at home who may not be able to protect themselves. Parents, caregivers, and others responsible for young children, the elderly, or people with mental health problems, need to make sure these individuals are kept warm. Also, any medications that could potentially cause hypothermia if taken in large doses should be stored safely away and out of reach.

Another is to make sure homes are well-heated, and to install all necessary safety measures if you’re using any form of fire for heat. The last strategy is to avoid doing things that could put you at higher risk of getting hypothermia. This includes activities like snowboarding or climbing mountains in cold places.