Unrecognized platelet physiology is the cause of rewarming deaths in accidental hypothermia and neonatal cold injury.

Background: The lack of improvement in prognosis of accidental hypothermia and neonatal cold injury suggests that a major cause of mortality has not been appreciated.

Aim Of The Article: To show that thrombocytopenia that deepens on rewarming under certain conditions is that missing factor.

Scientific Basis: Below 34 °C the first stage of aggregation is accentuated, the platelets are more sensitive to ADP and aggregation studies show an increased response "first stage hyper aggregation". We have confirmed that the irreversible second stage of platelet aggregation does not occur below 34 °C. On rewarming, the first stage of aggregation is followed by disaggregation. When platelets are warmed to 34 °C the potential exists for the platelets to undergo an irreversible second stage of aggregation "second stage platelet hyper aggregation" that can cause a further drop in platelet count and a bleeding diathesis. This only occurs if the platelets have been sufficiently primed when cold and may not be appreciated if platelet counts are not followed.

Significance Of This Data And Correlation With The Literature: This thesis explains many other open questions. Why has the overall prognosis remained without improvement over the last half century? Why hypothermic cardiac surgery is free of this problem? Why the depth of hypothermia is alone not prognostic? Has following platelet counts been associated with improved prognosis? Why cardiac arrest does not affect prognosis? Why some patients die suddenly after recovering from hypothermia? Why are so many different rewarming techniques used? Why is the prognosis better in hypothermic suicide attempts? What is the pathophysiological explanation for reversible sequestration of platelets to the liver and spleen in hypothermia? Is DIC (diffuse intravascular coagulation) a problem in hypothermia? And how this new approach could improve prognosis?

Conclusion: Prognosis can be improved by following platelet counts during rewarming. In patients with prolonged hypothermia, this will show a life-threatening drop in such counts easily treated by platelet infusion.