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

Drowning

Drowning and near drowning is a fascinating area. As a dinghy sailor, I regularly teach about drowning on our first aid courses, but as we sail on top of the water and not in the water, I've still never seen it! If you get a chance to watch the Cold Water Casualty video, it is well worth a watch. The Royal Yachting Association has a good summary about cold shock, hypothermia and drowning. The RNLI provides some UK statistics. Drowning is specifically mentioned in the cardiac arrest competencies, and in HAP11 Environmental emergencies (an adult competency).

WHO provides us a statistical summary about drowning, and Update in Anaesthesia provides a very thorough overview as does BMJ best practice, LITFL, EP monthly and the AHA.

There is an e-learning module on drowning here and here. Unless you are a Paramedic you're unlikely to have access to the former, and there are so many alternative resources out there I wouldn't subscribe. Enlighten me has an excellent CEMPedia article on drowning  and an adult case.


Statistics
Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid. In 2000, there were 409,272 deaths from unintentional drowning worldwide, decreasing slightly in 2004 to an estimated 388 000. 150 people drown in the UK coast every year - and 80% of these are male. Drowning is the second highest cause of death from injury, after road traffic injuries.

Young children are at risk as they are unaware of the dangers and less able to escape from water once submerged.

Things Drowning Causes
There are four main problems drowning causes:

• Hypothermia and Cold Water Shock
  Not everyone drowns in warm water! Hypothermia causes its own special problems. The most relevant problem is that blood gets diverted in to the core of the body - causing chilly blood outside, and warm blood inside. When you start to mix the warm and chilly blood, the body gets a bit confused - and arrhythmias can occur.
  Cold shock can happen at any water temperature below fifteen degrees - the average UK water temperature is twelve degrees.
• Associated injuries
  Remember to think about what people injured when they drowned themselves - neck and c-spine injuries are common.
  Awareness of injuries will be low because of natural adrenaline, and vasoconstriction in the extremities.
• Water aspiration
  As you hit the water, before the diving reflex is triggered, you get a gasp reflex (as you do when you first get in a really cold swimming pool!). If you enter turbulant water, as waves crash overhead you are even more likely to inhale some water. Aspiration of even small amounts of water significantly impairs gas exchange. The water dilutes and inactivates surfactant, so alveoli are prone to collapse. The water can also cause direct lung injury.
• Post rescue Collapse
  Loss of hydrostatic pressure of water on the body results in loss of peripheral resistance and venous pooling. Patients should be extricated from the water in a horizontal position.
• Post Drowning Infection
  Some people contract infections after drowning. Swamp water might cause fungal infection (aspergillosis)- so think about it in your poorly patients. Stagnant water with rat urine may cause Weil's disease (Leptospirosis). There are many case reports (1 2 3) about pneumonia after drowning - but there is still no evidence for prophylactic antibiotics.

Investigations
- ABG if significant history of submersion as saturations may not be reliable.
- CXR
- ECG - look closely for a prolonged QTc.
- Core temperature measurement
- Electrolytes and BM
- Blood culture in patients with significant aspiration

Treatment

• ABCD approach
• For children, no modifications to the resuscitation sequence are recommended.
• If intubation needed, ventilate using an ARDS protocol. 
• Observe for  at least six hours.
• After discharge, written discharge advice is well received by families. 
• There is no evidence to support giving prophylactic antibiotics on discharge.

PMP3: Cardiopulmonary Resuscitation

Paediatric Arrests don't happen often - but when they do we should be ready. The curriculum and summaries are on this page.
To have a look at the detailed posts and links for each topic, please go here.

The ALiEM summary on hypothermia is so good there's no point reinventing the wheel.For more hypothermia blog posts, please click here.

For more NLS blog posts, please click here.

For more PLS blog posts, please click here.

For more electrocution blog posts, please click here. 

For more blog posts on arrest drugs, please click here.

There are also posts on:
Venous Access 
SIDS
Drowning