Hypothermia

Question 1

Define hypothermia

Answer 1

Temp less than 35

Question 2

What are the risk factors for hypothermia

Answer 2

Elderly, homeless, alcohol, immersion, trauma

Question 3

Define mild moderate and severe hypothermia and describe how a patient would present

Answer 3

Mild 32-35 (normal mental state and shivering)
Moderate 28-32 (altered mental state and not shivering)
Severe 24-28 (unconscious with vital signs) or 13.7-24 (no vital signs)
Dead <13.7

Question 4

How does the ALS algorithm change for hypothermic patients?

Answer 4

CENTRAL pulse check for 1 minute (low pressure, low volume state means its harder to find)
Can also use ECG and Echo to determine signs of life
Harder compressions
Maximum 3 shocks until rewarmed to 30
No drugs below 30
Double interval between doses from 30-35

Question 5

How can you rewarm a hypothermic patient

Answer 5

Remove wet clothes
Dry
Cover in wool blankets or aluminium foil
Put in a warm environment
Warm IV fluids
Warm inspired air
Bladder lavage
VA ECMO
Exercise if possible

Question 6

When should ECMO for hypothermic patients be used?

Answer 6

Patient below 32 with potassium <8mmol/L

Question 7

Why is prognosis for a frozen patient good?

Answer 7

Decreased metabolic rate conserves ATP and oxygen so cells last longer before hypoxic damage

Question 8

At what temperature can a cold patient be pronounced dead?

Answer 8

32 is generally the cut off

Question 9

How do humans generate and lose heat?

Answer 9

Generated by cellular metabolism primarily in the liver

Lost by convection (currents of air), conduction (adjacent surface), radiation and evaporation (of sweat)

Question 10

What does the hypothalamus stimulate when low temperature is detected?

Answer 10

Shivering
Increased sympathetic drive
Stimulates thyroid
Peripheral vasoconstriction

Ultimately leads to increased metabolism, CO and ventilation

Question 11

At what temperature does metabolism drop and shivering stop?

Answer 11

32

Question 12

What are the physiological effects of hypothermia?

Answer 12

Bradycardia 
Hypotension 
Low minute volume (tidal volume x RR)
Arrhythmia (AF progress to VF to CA)
J waves on ECG
Peripheral vasoconstriction 
Hypoglycaemia progressing to hyperglycaemia
Cold diuresis (reduced ADH)

Question 13

Why do you get arrhythmias in hypothermia?

Answer 13

Difference in temperature across the myocardium leads to variability in electrical conduction

Question 14

Why are hypothermic patients hypotensive?

Answer 14

Bradycardic
Low volume
Reduced myocardial contractility

Question 15

What happens to glucose levels in hypothermic patients?

Answer 15

Initially hypo because shivering uses it up

Progress to hyper because insulin used up + there is insulin resistance

Question 16

How is hypothermia diagnoses

Answer 16

Oesophageal probe placed in lower 1/3 of oesophageal

Rectal probe often more practical and available

Question 17

What changes to CPR should be made in a patient <28 degrees

Answer 17

Intermittent CPR can be carried out

5 minutes of CPR followed by <5 minutes no CPR

Question 18

Why does a hypothermic patient being rewarmed need fluids

Answer 18

As they rewarm they will vasodilate

Question 19

Is rectal temperature (hypothermia) recommend or not and why

Answer 19

No - it lags behind core temperature

Question 20

Will tympanic temperature readings be higher or lower than core

Answer 20

Depends on environment and things in the EAM eg snow

Question 21

Primary goal prehospitally for hypothermic patients is…

Answer 21

Get them out of the environment - shouldn’t prolong transport with any treatments or investigations as most patients will continue to drop their temperatures and you need to get them out of there

Question 22

What is the effect of cold diuresis on electrolytes?

Answer 22

Hypophosphataemia, hypokalaemia, hypomagnasaemia, hypocalcaemia