text: It is usually recommended not to declare a person dead until their body is warmed to a near normal body temperature of greater than , since extreme hypothermia can suppress heart and brain function. This is summarized in the common saying "Youre not dead until youre warm and dead." Exceptions include if there are obvious fatal injuries or the chest is frozen so that it cannot be compressed. If a person was buried in an avalanche for more than 35 minutes and is found with a mouth packed full of snow without a pulse, stopping early may also be reasonable. This is also the case if a person's blood potassium is greater than 12 mmol/L.
  Those who are stiff with pupils that do not move may survive if treated aggressively. Survival with good function also occasionally occurs even after the need for hours of CPR. Children who have near-drowning accidents in water near  can occasionally be revived, even over an hour after losing consciousness. The cold water lowers the metabolism, allowing the brain to withstand a much longer period of hypoxia. While survival is possible, mortality from severe or profound hypothermia remains high despite optimal treatment. Studies estimate mortality at between 38% and 75%.
  In those who have hypothermia due to another underlying health problem, when death occurs it is frequently from that underlying health problem.