Workup for Chronic Hypothermia
The workup for chronic hypothermia should follow a structured approach based on severity classification, with initial assessment of core body temperature and evaluation for underlying causes, followed by implementation of appropriate rewarming strategies based on temperature severity. 1, 2
Initial Assessment
- Obtain accurate core body temperature measurement using low-reading thermometers, as clinical presentation may not always correlate with actual temperature severity 3
- Classify hypothermia based on core temperature:
- Cold stress (35-37°C)
- Mild hypothermia (32-35°C)
- Moderate hypothermia (28-32°C)
- Severe hypothermia (<28°C)
- Profound hypothermia (<24°C) 1
- Assess for immediate life-threatening complications:
- Cardiac arrhythmias (particularly atrial fibrillation)
- Coagulopathy
- Central nervous system depression 4
Diagnostic Evaluation
- Conduct thorough evaluation for underlying causes:
- Environmental exposure (most common cause)
- Metabolic derangements
- Endocrine dysfunction
- Infections
- Central nervous system disorders
- Toxin exposure 5
- Laboratory studies should include:
- Complete blood count
- Comprehensive metabolic panel
- Thyroid function tests
- Cortisol levels
- Blood cultures if infection suspected 5
- Additional diagnostics:
- ECG to assess for Osborn waves and arrhythmias
- Chest radiograph to evaluate for pneumonia
- Urinalysis to assess for infection 3
Treatment Algorithm
Mild Hypothermia (32-35°C)
- Remove wet clothing immediately
- Move to warm environment
- Apply warm blankets
- Provide high-calorie foods/drinks if patient is alert
- Monitor for deterioration 1, 2
Moderate Hypothermia (28-32°C)
- Continue all measures for mild hypothermia
- Implement active external rewarming:
- Heating pads
- Forced warm air blankets
- Chemical heat blankets
- Administer warmed intravenous fluids
- Provide humidified, warmed oxygen 1, 2
Severe/Profound Hypothermia (<28°C)
- Continue all measures for moderate hypothermia
- Activate emergency response system
- Consider active core rewarming methods:
- Warmed intravenous fluid infusions
- Peritoneal lavage with warmed fluids
- Extracorporeal blood warming for profound cases
- Handle patient gently to avoid triggering arrhythmias 1, 2, 6
Rewarming Considerations
- Target rewarming to a minimum core temperature of 36°C before transferring between units 1, 2
- Cease rewarming after reaching 37°C as higher temperatures are associated with poor outcomes 1, 2
- Natural rewarming rate is approximately 1.20°C/h, while shivering can increase the rate up to 3.6°C/h 2
- For rapid induction of rewarming, combine cold fluid infusion (1500-3000 mL of 4°C saline or Ringer's lactate) with an invasive or surface cooling device 7
Monitoring During Rewarming
- Continuous cardiac monitoring for arrhythmias
- Regular assessment of core temperature every 5-15 minutes depending on severity
- Monitoring for electrolyte abnormalities, particularly potassium, calcium, and magnesium
- Assessment for signs of rewarming shock 8, 2
Special Considerations
- Avoid aggressive rewarming in severe hypothermia as it may lead to rewarming shock and cardiovascular collapse 4
- Monitor for complications during rewarming:
- Cardiac arrhythmias
- Coagulopathy
- Burns from improper use of active external rewarming devices 1
- Early implementation of rewarming protocols has been shown to significantly reduce morbidity and mortality 2
Prevention Strategies
- Emphasis should be on prevention first and treatment second, as it becomes increasingly difficult to rewarm patients once significant heat is lost 2
- For at-risk individuals, implement preventive measures:
- Appropriate clothing
- Adequate shelter
- Nutritional support
- Education about early recognition of symptoms 5