What are the causes of hypothermia?

Causes of Hypothermia

Hypothermia is caused by exposure to cold environments, trauma, medical conditions, and iatrogenic factors that lead to heat loss exceeding the body's ability to generate and retain heat. Understanding these causes is crucial for prevention, early recognition, and appropriate management to reduce morbidity and mortality.

Environmental Causes

• Cold exposure: Direct exposure to cold environments, especially in combination with wet conditions 1
• Inadequate clothing: Lack of proper insulation or wearing wet clothing that accelerates heat loss 1
• Immersion: Contact with cold water, which conducts heat away from the body 25 times faster than air
• Wind chill: Increases convective heat loss from the body surface

Trauma-Related Causes

• Severe injuries: Blood loss, large open wounds, and significant head injuries disrupt temperature regulation 1
• Shock: Hypoperfusion leads to decreased heat production and impaired thermoregulation
• Open body cavities: Exposure of internal organs during surgery or trauma accelerates heat loss 1
• Burns: Extensive skin damage impairs the body's ability to regulate temperature

Medical Conditions

• Endocrine disorders: Hypothyroidism, hypopituitarism, hypoglycemia 1
• Neurological conditions: Spinal cord injuries, stroke, or hypothalamic dysfunction 2
• Metabolic disorders: Malnutrition, hypoadrenalism, hypoglycemia 3
• Infections: Sepsis can initially present with hypothermia, especially in elderly patients
• Age-related factors: Very young and elderly have reduced thermoregulatory capacity 1

Iatrogenic and Treatment-Related Causes

• Medication effects:

  • Sedatives and anesthetics impair thermoregulation and reduce shivering 1
  • Vasodilators increase heat loss through the skin
  • Neuromuscular blockers prevent shivering 1

• Medical procedures:

  • Infusion of cold fluids (temperature below 21°C) 1
  • Prolonged surgery with exposure of body cavities 1
  • Ventilation with cold gases 1
  • Induction of anesthesia (typically decreases temperature by 1°C within 30 minutes) 1

• Therapeutic hypothermia: Intentional cooling for neuroprotection after cardiac arrest 1

Substance-Related Causes

• Alcohol intoxication: Causes peripheral vasodilation and impairs judgment about cold exposure 3
• Drug use: Various substances can impair thermoregulation 1

Risk Factors for Developing Hypothermia

• Advanced age: Elderly have reduced thermoregulatory capacity and impaired perception of cold 1
• Homelessness: Prolonged environmental exposure without adequate shelter 1
• Severity of injury: Higher injury severity scores correlate with increased risk of hypothermia 1
• Prehospital intubation: Associated with 5.18 times higher odds of developing hypothermia 1
• Hypotension: Systolic blood pressure <100 mmHg increases risk (OR 3.04) 1

Clinical Progression of Hypothermia

Hypothermia progresses through predictable stages 1:

• Cold stress (35-37°C): Alert, possibly shivering
• Mild hypothermia (32-35°C): Altered responsiveness, shivering
• Moderate hypothermia (28-32°C): Decreased responsiveness, with or without shivering
• Severe hypothermia (<28°C): Unresponsive, may appear lifeless
• Profound hypothermia (<24°C): Cessation of shivering, slow heart rate and breathing, high risk for cardiac arrest

Prevention Strategies

• Wearing proper layered clothing (moisture-wicking base layers, wool/fleece middle layers, moisture-repellent outer layers) 4
• Removing wet clothing promptly 1
• Using warmed fluids during resuscitation 1
• Maintaining appropriate ambient temperature during procedures 1
• Monitoring core temperature during anesthesia and surgery 1
• Implementing active warming measures for at-risk patients 1

Understanding the multifactorial causes of hypothermia is essential for implementing appropriate preventive measures and treatment strategies to reduce the significant morbidity and mortality associated with this condition.