Hypothermia: Symptoms, Types, Causes and Treatment

Hypothermia is a potentially life-threatening condition that occurs when the body's core temperature drops below the normal range required to maintain healthy physiological function. While it is often associated with exposure to cold environments, hypothermia can arise in a surprising variety of settings and can affect anyone, from newborns to the elderly. In this article, we’ll explore the symptoms, types, causes, and treatment of hypothermia, synthesizing the latest research and clinical insights.

Symptoms of Hypothermia

Recognizing the symptoms of hypothermia early is crucial for prompt intervention and prevention of severe outcomes. Symptoms can be subtle at first but become more pronounced as the core body temperature continues to fall.

Symptom	Description	Severity Level	Source(s)
Shivering	Involuntary muscle contractions	Mild to moderate	1 3 4
Lethargy	Unusual tiredness or fatigue	Mild to severe	1 3
Confusion	Impaired thinking, disorientation	Moderate to severe	1 2 3
Poor Coordination	Clumsiness, stumbling	Moderate to severe	1 3
Slowed Heart/Respiration	Reduced pulse and breathing rate	Severe	1 3 4
Unconsciousness	Loss of awareness, coma	Severe	2 3

Table 1: Key Symptoms of Hypothermia

Understanding the Signs

Hypothermia develops when the body loses heat faster than it can produce it, causing core temperature to dip below 35°C (95°F) 1 3 4. Symptoms often begin subtly and worsen as the temperature drops further.

Early Symptoms

• Shivering: The body's first defense, shivering is an automatic response designed to generate heat through muscle activity. Persistent shivering is a hallmark of mild hypothermia 1 3.
• Lethargy and Weakness: As the body’s temperature drops, energy levels plummet, leading to unusual fatigue and sluggishness 1 3.

Progressive Symptoms

• Confusion and Poor Coordination: As hypothermia progresses, brain function becomes impaired. People may appear confused, have difficulty speaking, or stagger when walking 1 2 3.
• Loss of Fine Motor Skills: Tasks like buttoning a shirt or holding objects may become difficult 3.

Severe Symptoms

• Slowed Heart Rate and Breathing: With severe hypothermia, the heart and lungs slow dramatically, increasing the risk of life-threatening complications 1 3 4.
• Unconsciousness and Coma: Eventually, the person may become unresponsive, slip into a coma, or even die if not treated promptly 2 3.

Special Populations

• Neonates and Infants: Newborns may not shiver but become limp, quiet, and feed poorly 6.
• Elderly: Older adults may not feel the cold as intensely, and their symptoms may be mistaken for dementia or stroke 1 7 8.

Types of Hypothermia

Not all cases of hypothermia are the same. Understanding the different types can help in tailoring prevention and treatment strategies.

Type	Definition / Criteria	Distinct Features	Source(s)
Mild Hypothermia	Core temperature 32–35°C (89.6–95°F)	Shivering, confusion	3 4 7
Moderate Hypothermia	Core temperature 28–32°C (82.4–89.6°F)	Slowed speech, drowsiness	3 4 7
Severe Hypothermia	Core temperature <28°C (<82.4°F)	Loss of consciousness	3 4 7
Accidental Hypothermia	Unintentional drop in temperature	Environmental exposure	4 7 8
Secondary Hypothermia	Due to medical conditions or substances	Linked to underlying cause	3 4
Neonatal Hypothermia	Hypothermia in newborns (<36.5°C [97.7°F])	High risk in infants	6
Paroxysmal Hypothermia	Recurrent spontaneous hypothermia episodes	Often linked to brain lesions	2

Table 2: Types of Hypothermia

Classification by Severity

Hypothermia is typically grouped into three categories based on core body temperature 3 4 7:

• Mild: Characterized by shivering, confusion, and impaired judgment.
• Moderate: Shivering may stop, coordination worsens, and the person may become drowsy.
• Severe: Loss of consciousness, very slow breathing and heart rate, and risk of cardiac arrest.

Accidental vs. Secondary Hypothermia

• Accidental Hypothermia: Results from unintentional exposure to cold environments, such as falling into cold water or being stranded outdoors in winter. This is the most common scenario 4 7 8.
• Secondary Hypothermia: Occurs due to underlying medical conditions (e.g., hypothyroidism, stroke) or certain drugs (e.g., alcohol, sedatives) that impair heat production or increase heat loss 3 4.

Special Types

• Neonatal Hypothermia: Newborns, especially in low-resource settings, are highly susceptible due to their large surface area relative to body weight and underdeveloped thermoregulation 6.
• Paroxysmal Hypothermia: Rare, involving spontaneous, recurrent hypothermia episodes, sometimes linked to specific brain lesions or epilepsy 2.

Causes of Hypothermia

Hypothermia can develop from a wide array of causes, both environmental and medical. Understanding these factors is essential for effective prevention and intervention.

Cause Category	Example Causes	High-Risk Populations	Source(s)
Environmental	Cold weather, immersion in water	Outdoor workers, homeless, elderly	1 4 7 8
Behavioral	Inadequate clothing, wet clothes	Children, substance users	1 7 8
Medical/Physiological	Endocrine/neurological disorders	Patients with chronic illnesses	3 4 2
Substance-related	Alcohol, sedatives, psychoactives	Substance abusers, elderly	1 8 7
Neonatal Factors	Poor thermal care, low birth weight	Newborns, preterms	6

Table 3: Major Causes of Hypothermia

Environmental Exposure

• Cold Weather: The most common cause. Prolonged exposure to cold air or water rapidly drains body heat. Wind and dampness increase risk 1 4 7 8.
• Water Immersion: Water conducts heat away from the body much faster than air, making immersion particularly dangerous 1 7.

Behavioral and Social Factors

• Inadequate Clothing: Wearing insufficient or wet clothing accelerates heat loss 1 7.
• Homelessness and Socioeconomic Factors: Those with limited access to shelter and heating are at greater risk, especially in low-population or low-socioeconomic regions 8.

Medical and Physiological Causes

• Underlying Illnesses: Disorders of the endocrine or central nervous system can affect the body’s ability to regulate temperature 3 4.
• Paroxysmal Hypothermia: Rare neurological syndromes, often after brain injury, can cause recurrent episodes 2.
• Neonatal Risks: Newborns can lose heat quickly due to their small size, thin skin, and lack of brown fat 6.

Substance Use

• Alcohol and Drugs: Alcohol impairs the body’s ability to sense cold and dilates blood vessels, increasing heat loss; sedatives and psychoactive drugs blunt normal responses to cold 1 7 8.
• Other Agents: Some medications or toxins can disrupt thermoregulation 3.

Special Populations

• Elderly: Reduced physiological reserve and impaired perception make older adults particularly vulnerable 1 7 8.
• Infants: Inability to shiver or communicate distress increases risk 6.

Treatment of Hypothermia

Prompt and appropriate treatment is vital for survival and recovery from hypothermia. The approach depends on the severity and the underlying cause.

Treatment Level	Description / Methods	Typical Setting	Source(s)
Passive External Warming	Move to warm environment, dry clothing	Mild cases, field care	3 4 7
Active External Warming	Warm blankets, heating devices	Moderate cases	3 4 7
Active Core Rewarming	Warmed IV fluids, heated oxygen, lavage	Severe hospital cases	3 4 7
Neonatal Interventions	Skin-to-skin care, incubators	Newborns	6
Avoiding Harmful Drugs	E.g., avoid benzodiazepines in PH	Special cases (PH)	2
Therapeutic Hypothermia	Controlled cooling (e.g., after cardiac arrest)	ICU/cardiac arrest	9 11 12 13

Table 4: Treatment Approaches for Hypothermia

Initial Steps

• Remove from Cold and Wet: The first priority is to move the individual to a warm, dry environment and remove any wet clothing 3 4 7.
• Passive Warming: For mild hypothermia, covering with blankets and offering warm (non-alcoholic) fluids can be effective 3 4.

Active External and Core Rewarming

• Active External Warming: Use of heating blankets, warm packs, or other devices to raise skin temperature 3 4 7.
• Active Core Warming: In severe cases, medical interventions like warmed intravenous fluids, heated humidified oxygen, peritoneal or thoracic lavage, or even extracorporeal blood warming may be needed 3 4 7.

Special Considerations

• Neonatal Care: Skin-to-skin contact, radiant warmers, and incubators are essential for newborns. Prevention is key, especially in low-resource settings 6.
• Avoid Harmful Medications: In rare cases like paroxysmal hypothermia, misdiagnosis can lead to inappropriate treatment (e.g., benzodiazepines may worsen symptoms) 2.

Therapeutic and Induced Hypothermia

Interestingly, controlled hypothermia is sometimes deliberately induced as a medical therapy, particularly after cardiac arrest, to protect the brain and improve outcomes 9 11 12 13. This is done in a hospital setting using specialized devices and protocols.

• Therapeutic Hypothermia: Targeted temperature management (e.g., cooling to 32–34°C) after cardiac arrest has been shown to improve survival and neurological outcomes in adults, especially those with shockable heart rhythms 9 12 13.
• Children: Studies show mixed results; some trials did not find a significant benefit in pediatric populations 10.

Monitoring and Complications

• Cardiac Monitoring: Severe hypothermia can lead to dangerous heart rhythms; continuous monitoring is required 11.
• Infection Risk: Lowered body temperature impairs immune responses, raising the risk of infection during and after treatment 11.
• Rewarming Shock: Careful, gradual rewarming is critical to avoid complications like low blood pressure or arrhythmias 11.

Conclusion

Hypothermia is a complex, preventable medical emergency that demands awareness and swift action. Whether it arises from environmental exposure, underlying health issues, or rare neurological conditions, understanding its symptoms, types, causes, and treatments can save lives.

Key Points:

• Hypothermia symptoms progress from shivering and confusion to severe unconsciousness and slowed vital signs 1 3 4.
• Types of hypothermia include mild, moderate, severe, accidental, secondary, neonatal, and rare paroxysmal forms 3 4 6 7 2.
• Main causes are environmental exposure, inadequate protection, medical conditions, substance use, and age-related vulnerabilities 1 3 4 7 8 6.
• Treatment ranges from passive warming to aggressive medical interventions; prevention and special care for vulnerable groups are essential 3 4 6 7.
• Controlled (therapeutic) hypothermia is sometimes used in critical care to improve outcomes after cardiac arrest, especially in adults 9 11 12 13.

By recognizing the signs and knowing how to respond, we can reduce the toll of hypothermia and protect those most at risk.