Room temperature ADP-induced first-stage hyperaggregation of human platelets: the cause of rewarming deaths by thrombocytopenia in neonatal cold injury.

No satisfactory explanation has been proposed to explain the rewarming deaths common in neonatal cold injury (NCI). Since thrombocytopenia exists in NCI, aggregation studies were performed on human platelets at the relevant temperatures to search for a mechanism that would link thrombocytopenia with this complication. At the temperatures found in infants suffering from NCI, an increased sensitivity to ADP was noted: room-temperature ADP-induced first-stage hyperaggregation. Evidence exists to suggest that adequate release of ADP from erythrocytes occurs in vivo to cause such aggregation. Hypothermic platelets on being rewarmed undergo a second stage of irreversible aggregation that correlates well with the postwarming drop in platelet count seen in NCI and offers an explanation of the massive pulmonary hemorrhage and other bleeding phenomena seen in infants who die while being rewarmed.