What are the causes of hypothermia?

Causes of Hypothermia

Hypothermia results from two broad categories: primary (accidental) hypothermia from environmental cold exposure, and secondary hypothermia from underlying medical conditions, with acute medical illness and infection being the most common secondary causes in clinical practice.

Primary (Accidental) Hypothermia

Environmental exposure to low ambient temperatures represents the most straightforward cause, accounting for approximately 44% of cases in older adults 1. This occurs when heat loss exceeds the body's ability to generate warmth, particularly in:

• Prolonged cold exposure without adequate protection
• Immersion in cold water
• Vulnerable populations: elderly patients (who have impaired thermoregulation), young children (higher surface area-to-mass ratio, ineffective sweat glands), and homeless individuals 2, 3

Secondary Hypothermia: Medical Causes

Secondary hypothermia develops from underlying pathologic conditions that impair thermoregulation or increase heat loss 4. The most critical causes to identify include:

Infectious/Inflammatory Causes

• Sepsis and acute infections (incidence 10-32% in hypothermic patients) 1
• Acute medical illness (49-51% of secondary hypothermia cases) 1

Endocrine Dysfunction

• Severe hypothyroidism (myxedema coma) - a life-threatening cause that must not be missed 3, 1
• Diabetic ketoacidosis 3
• Adrenal insufficiency

Neurological Causes

• Acute spinal cord injury (disrupts autonomic thermoregulation) 3
• Central nervous system dysfunction 4
• Stroke or other brain injuries

Trauma and Toxicology

• Multisystem trauma (up to 14% incidence) 3, 1
• Alcohol intoxication (5-26% of cases - dominant precipitating factor) 1, 5
• Drug-induced hypothermia from sedatives, antipsychotics, or other medications 1, 4
• Cocaine and sympathomimetic poisoning 2

Cardiovascular

• Prolonged cardiac arrest 3
• Shock states 6

Clinical Pitfalls to Avoid

Do not assume environmental exposure is the only cause. In older patients presenting to emergency departments with hypothermia, systematically evaluate for:

1. Infection/sepsis first - most common treatable cause requiring immediate antibiotics 7
2. Thyroid failure - check TSH and free T4 urgently
3. Medication review - sedatives, antipsychotics, alcohol
4. Trauma history - even minor falls in elderly
5. Neurological examination - for stroke or spinal cord pathology

The mortality associated with hypothermia is substantial (approximately 20,000-25,000 deaths annually in developed countries), with unofficial numbers likely higher, particularly in elderly populations 5. Deaths during rewarming often result from inappropriate or ineffective treatment rather than the hypothermia itself 5.

Key principle: If a patient presents with hypothermia and no obvious environmental exposure, aggressively pursue secondary causes, starting with infection and endocrine dysfunction, as these require specific interventions beyond rewarming alone 1, 7.