He or she needs a gentle source of heat, like another human body. Apply hot packs to the neck, armpits, sides, chest and groin. Keep the head covered. Do not warm, rub or stimulate the severely hypothermic patient's extremities. This may bring cold, stagnant blood from the body surface to the body core, resulting in cardiac arrest.
Hot drinks are also dangerous as they draw warm blood away from vital organs.
Acidosis occurs as the acid waste products from cell metabolism in the extremities is returned to the heart, which may result in re-warming shock. Both afterdrop and acidosis may precipitate cardiac arrest. Bystanders may be tempted to start CPR on a severe case as it is very difficult in the field to distinguish between severe hypothermia and cardiac arrest. But chest compressions or any other rough handling of a severely hypothermic person are particularly likely to convert a slow, low output heart rhythm into ventricular fibrillation, a form of heart attack. Therefore, to reduce heat loss, protect these areas.