Hypothermia

Disclaimer These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.  Read the full PCH Emergency Department disclaimer.

Aim 

To guide staff with the assessment and management of hypothermia.

Definition

Hypothermia is core temperature < 35°C. Young children are at risk due to high body surface area to weight ratio.

Background 

• Hypothermia is usually due to environmental causes e.g. immersion and exposure.
• Check core temperature using a rectal or oesophageal thermometer.
• Be aware that sepsis may present with hypothermia.

Temperature	Clinical effects
32°C	Decreased pulse / respiratory rate / BP / conscious state Shivering stops. Muscle rigidity (may mimic rigor mortis) Atrial arrhythmias appear – usually innocent and revert when rewarmed
28°C	Ventricular arrythmias (including VF) Fixed dilated pupils
26°C	Comatose Absent reflexes Apnoea
20°C	Asystole
15°C	Temperature of the coldest known survivor

Hypothermia in resuscitation

• Hypothermia substantially reduces effectiveness of defibrillation and resuscitation drugs. It is reasonable to attempt defibrillation, but if unsuccessful, continue cardiac compression until core temperature is > 30°C, when defibrillation / drugs are more likely to be effective.
• Drugs are generally withheld until core temperature is >30°C, as accumulation may occur while cold, with resultant toxicity when rewarmed.
• Never diagnose death and thus stop resuscitation until the patient is rewarmed to at least 32°C or cannot be rewarmed despite active measures.

 

Assessment

• Monitor core temperature
• Monitor heart rate and rhythm
• Check electrolytes and glucose.

Management

Important Principles

• Actively rewarm to 32°C, then allow passive rewarming. Once above the fibrillation threshold (32°C) there is no urgency in rewarming
• Mild brain hypothermia may limit reperfusion injury
• Avoid hyperthermia (keep temperature < 36.5°C)
• Never diagnose death and thus stop resuscitation until the patient is rewarmed to at least 32°C, or cannot be rewarmed despite active measures
• Beware: rewarming may lead to vasodilation and hypotension (so-called 'after shock'), which can contribute significantly to mortality
• Beware: Peripheral rewarming and vasodilation can result in cold, acidotic blood being shunted to the core, with a drop in core temperature (so-called 'after drop') and an increased risk of arrhythmias
• Hypokalaemia is common, even in the presence of marked acidosis
• Check blood gases, potassium, glucose, and haematocrit with every few degrees of warming.

 

External rewarming (for temperature > 32°C)

• Passive external rewarming:
  • remove wet clothes, dry patient
  • warm blankets
  • cover with sheet of foil/space blankets
• Active external rewarming (truncal areas only):
  • overhead warmers
  • warm air system e.g. Bair Hugger
  • thermal mattresses.

 

Active core rewarming (for temperature < 32°C)

• Warm IV fluids to 39°C with blood warmer (slow) - start with pre-warmed IV 0.9% saline at 40°C
• Gastric or bladder lavage with 0.9% saline at 40°C
• Peritoneal lavage with potassium-free dialysate or 0.9% saline at 40°C. Use 20 mL/kg cycled every 15 minutes
• Ventilation with humidified gas heated to 42°C
• Pleural or pericardial lavage
• Haemodialysis, extra-corporeal blood warming.

 

Bibliography

1. Cullough L, Arora S (Dec 2004). "Diagnosis and treatment of hypothermia". Am Fam Physicican
2. Textbook of Paediatric Emergency Medicine 2nd Edition Cameron Elesevier
3. Nelson Textbook of Pediatrics: 20th Edition Robert M. Kliegman, Bonita M.D. Stanton, Joseph St. Geme, Nina F Schor Publisher: Elsevier

Endorsed by:	Executive Director, Medical Services	Date:	Oct 2021
		Review date:	Oct 2022

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