Hypothermia

Related Subjects: Acute Kidney Injury | Acute Rhabdomyolysis | Hyperkalaemia

You're not dead until you're warm and dead. It is important to note that some may be young and have more scope for survival

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About

• Definition: An unintentional fall in core body temperature < 35°
• Use a low reading rectal thermometer
• Hypothermia: < 35°C. Moderate < 32°C. Severe Hypothermia < 28°C

Risks

• Less common in UK due to temperate climate. Common in colder climates
• Can be seen with winter sports and wilderness enthusiasts and often young
• Also seen urban poor/homeless + alcohol, drugs, malnutrition and poor socioeconomic conditions
• Another group at risk is exposure with prolonged surgery
• Can be a method of attempted suicide

Hypothermia occurs when the body’s core temperature falls below 35°C. Infants/Children are susceptible because they have poor thermoregulation and a high body surface area-to-weight ratio, but the elderly are at highest risk.

Clinical

• Elderly are at highest risk of accidental hypothermia
• Mild hypothermia: reflex shivering, desire to put on warm clothes and turn up heating.
• Moderate: Mild ataxia, confusion and dehydration. Little attempt to reduce heat loss.
• Severe: Bradycardia, hypotension.
• Below < 28 C: Coma, absent pupillary responses, absent corneal reflex, cardiac standstill
• Can be seen as part of stroke or falls when patients become incapacitated in a cold environment. Consider CT scan. Check Capillary blood glucose

Causes

• Falls, stroke, Confusion, Wandering, Alcohol, sedation and drug taking
• Poverty and no heating in winter, Homelessness
• Could this be Hypothermia and
• Stroke (get CT)
• Brain injury (get CT)
• Drugs: alcohol, opiates, benzodiazepines
• Carbon monoxide poisoning
• Alcohol excess: DTs later
• Drowning, Electrocution
• Myxoedema coma
• Hypoglycaemia (Diabetic)

Investigations

• FBC: ↑↑ Haematocrit ↑ WCC
• U&E: ↑Urea, ↑ creatinine dehydration. ↑↑ as a consequence of rhabdomyolysis or AKI or both. Arrhythmias are possible so telemetry and treat.
• ECG: classic J or Osborne waves (see above), AF or VF/VT. ↑↑ K changes
  • Bradycardia
  • 'J' wave . small hump at the end of the QRS complex
  • First degree heart block
  • Long QT interval
  • Atrial and ventricular arrhythmias
• ↑↑ CK from fall and lying on floor
• Blood gases: Metabolic acidosis
• TFT: exclude hypothyroidism can cause hypothermia ↑ TSH
• Cortisol: if Addison's considered
• ↑Amylase from Pancreatitis
• Toxicology screen: drugs taken
• Measure COHb: Carbon monoxide poisoning

Electrocardiogram

Height of the Osborne wave is roughly proportional to the degree of hypothermia

Management (expert help needed)

• ABC. Get IV access. Telemetry. Keep covered after the full survey. Warm fluids without K. High FiO2. Closely watch ABG and K+ and CBT.
• Mild 32-35C then warm blankets and drinks if able.
• Severe < 32 C then needs ITU/HDU bed and warmed fluids via NG tube. Warm peritoneal fluids. Cardiac bypass can be used. Risk of cardiac arrest. Warm fluids can be given to Pleural, peritoneal spaces or bladder lavage with warmed fluids. Heart bypass for some ECMO.
• Hot baths run the risk of falls in BP with vasodilation also impossible to defibrillate. It may be considered for immersion victims. Some have tried
• Cardiac arrest: Full resuscitation facilities must be available - may need defibrillation. Do not declare the patient as dead until the Core temperature is normal. Need to be warm and dead is the old adage before stopping resuscitation
• Steroids/Thyroxine: If any possibility of hypoadrenalism and/or hypothyroidism and myxoedema coma then give IV steroids +/- T3 as needed. Consider IV dextrose, Thiamine, Naloxone.

References

• Diagnosis and Treatment of Hypothermia 2004