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.

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Aim

To guide Emergency Department (ED) staff with the assessment and management of hypothermia.

Definition¹

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. Refer to Sepsis Recognition and Management (ED Guideline)

Effects of hypothermia²

Temperature	Clinical effects
32°C	Decreased pulse, respiratory rate, blood pressure and/or 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 resuscitation³

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^1,2,4,5,6

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)
Beware: rewarming may lead to vasodilation and hypotension (so-called 'after shock'), which can contribute significantly to mortality. Aim to warm no faster than 1-2 ºC per hour
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. 3M^™ 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 sodium chloride 0.9% at 40°C
Gastric or bladder lavage with sodium chloride 0.9% at 40°C
Peritoneal lavage with potassium-free dialysate or sodium chloride 0.9% 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.

Nursing considerations

Aim to warm no faster than 1-2 ºC per hour (NB: Rapid rewarming may cause vasodilation and consequently hypotension.)^1,2
Monitor the patient’s temperature 15-30 minutely via axilla / tympanic thermometer or continuously with the reusable or single use Phillips™ oesophageal temperature probe (refer to PCC targeted temperature management).
Lower the temperature setting of the Bair Hugger™ if the patient is warming too quickly.
Turn off Bair Hugger™ once normothermia is reached. The blanket may be left in situ.
Skin must be inspected 1-2 hourly for potential thermal and pressure injury.
Patients must be kept dry as warming will be less effective if patient is damp³
Eyes should be protected by lubricant or patches when overhead warming devices in use ³

References

Corneli HM, Kadish H, Hypothermia in Children: Clinical Manifestations and Diagnosis. UpToDate. [Last updated: 16 September 2023. Cited 4 October 2023} Available from: Hypothermia in children: Clinical manifestations and diagnosis - UpToDate (health.wa.gov.au)
Hazinski, M F. Nursing Care of the Critically Ill Child. Missouri: Elsevier Mosby; 2013
Acworth J, Nuthal G, Aickin R (2021) ANZCOR Guideline 12.4 – Paediatric resuscitation in special circumstances. guideline-12-4-paediatric-resuscitation-in-special-circumstances-257.pdf (anzcor.org)
Hockenberry, M J, Wilson, D. Wong’s Nursing Care of Infants and Children. Missouri: Elsevier Mosby; 2015
McCullough L, Arora S (Dec 2004). "Diagnosis and treatment of hypothermia". Am Fam Physician
Textbook of Paediatric Emergency Medicine 3rd Edition Cameron P, Browne GJ, Mitra B, et al (2018) Publisher: Elsevier Edition updated
Nelson Textbook of Pediatrics: 21st Edition Robert M. Kliegman, St Geme JW, Blum MJ et al. 2020 Publisher: Elsevier
GE Healthcare. Warmers [Internet]. Australia: General Electric Company; 2017. Available from http://www3.gehealthcare.com.au/en-au/products/categories/perinatal_care/warmers

Endorsed by:	Co-director, Surgical Services (Nursing)	Date:	Oct 2023
		Review date:	Oct 2026

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