Hypothermia

We're all used to deliberately inducing hypothermia in patients who have had an arrest, or similar - but not so used to treating hypothermia. For a good environment based start to your hypothermia training, there are plenty of Wilderness Medicine and Polar Medicine courses about.

EnlightenMe has got a lot of resources on hypothermia. Most of them are about adults, but that is better than nothing! e-LfH has a module on hypothermia too. We have some learning about ECG changes, a CEMPedia article, CEMPedia on cardiac arrest in special circumstances. BMJLearning has two modules - hypothermia for Paramedics and accidental hypothermia which has an excellent list of things that predispose people to hypothermia. LITFL also talks about ECG changes, as does Circulation- the height of the Osbourn wave is proportional to the degree of hypothermia.

There is a podcast here, a LITFL summary, and an abbreviation heavy summary here on crashing patient. There is an excellent summary here on Academic Life in Emergency Medicine. There are also some well thought of videos here.

For those who are wondering whether it's all worth it or not, there is a brilliant video about a hypothermia survivor.

Statistics
In Great Britain, hypothermia cases are estimated at 6-8 patients per 1000 patients Most cases of hypothermia occur in an urban setting and are related to environmental exposure attributed to alcoholism, illicit drug use, or mental illness, often exacerbated by concurrent homelessness.

Primary hypothermia usually affects young males and infants. Secondary hypothermia usually affects patients who are elderly, homeless, mentally ill, victims of trauma, or have multiple co-morbidity.

Older adults are at risk of hypothermia as a consequence of:

• A reduced ability to recognise and respond to lower ambient temperature, compared with younger adults. 
• An impaired peripheral vasoconstrictor response to cold.
• A lower basal metabolic rate compared with younger adults. 
• Falls, which are common in older people can result in prolonged periods lying on the floor, allowing heat loss by conduction.

Signs and Symptoms
There are plenty of signs and symptoms of hypothermia - some of which are subtle, others aren't.
Shivering
Impaired judgement
Confusion
Tachycardia
Tachypnea

Bradycardia
Respiratory depression
Hyperglycaemia
Dysarthria
Ataxia

Stupor
Lethargy
Osbourne Waves on the ECG - ( Osborn or J waves on the ECG. The upward deflection of the terminal S wave)
Loss of reflexes
Hypotension
Asystole

Treatment

• ABCD approach
• Handle carefully
• In general, the hypothermic patient is dehydrated and fluid depleted consider a fluid challenge of warmed 0.9% saline or dextrose-saline as they may also be hypoglycaemic. Hartmann’s is best avoided as the hypothermic liver can't metabolise lactate. 
• Passive Rewarming
• Active Rewarming
• Core Rewarming - IV fluids and warm, humidified oxygen
• Extracorporeal Blood Rewarming

In cardiac arrest
 - Total of three shocks (if indicated) until core temperature greater than 30degrees.
 - No drugs under 30degrees, then given with twice the time interval until normothermia
 - Chest compressions may be harder work.

Investigations
Urea & electrolytes
Full blood count
Clotting screen,
Arterial blood gas
Creatinine kinase level
Calcium
Magnesium
Amylase