Graded by core temperature, rewarmed according to severity
Expansion
Grading by core temperature
- Mild, 32 to 35 - shivering, tachycardia, vasoconstriction, confusion
- Moderate, 28 to 32 - shivering stops, bradycardia, reduced consciousness, dilated pupils, arrhythmia risk
- Severe, below 28 - coma, areflexia, ventricular fibrillation and asystole
ECG: bradycardia, J (Osborn) waves at the QRS-ST junction, prolonged intervals, atrial fibrillation and ventricular arrhythmia.
Rewarming
- Passive external: remove wet clothing, insulate, warm environment. Mild cases
- Active external: forced air warming blankets
- Active internal: warmed intravenous fluids, warm humidified oxygen, lavage, and extracorporeal rewarming for severe cases or cardiac arrest
Handle gently: rough movement can precipitate ventricular fibrillation in the irritable cold myocardium.
In cardiac arrest, drugs and defibrillation are less effective below 30 degrees: withhold drugs below 30, and limit defibrillation to three attempts until warmer.
“No one is dead until warm and dead.” Full neurological recovery has followed prolonged arrest in hypothermia, particularly after cold water immersion in children, so resuscitation continues during rewarming.
Afterdrop is a paradoxical fall in core temperature as cold peripheral blood returns centrally during rewarming.