Clinical course of critically ill infants and children is sometimes complicated by unexpected thrombocytopenia following surgical interventions during anticancer therapies. The concen-tration of plasma β-TG and PF-4 which are considered to be the most sensitive markers of in vivo platelet activation was measured simultaniously with platelet count and aggregation in surgical patients, aged 20 days to 13 years, in order to evaluate the mechanisms of the loss of circulating platelet. In the case of thrombocytopenia induced by suppressed or impaired thrombogenesis of bone marrow resulting from sepsis or anticancer therapy, the levels of β-TG and PF4 remaind lower than normal range, however, those levels immediately increased following the improvement of bone marrow function. In the cases of Kasabach-Merritt syndrome, these proteins changed parallel with the size of hemangioma. In the case of idiopathic thrombocytopenic purpura (ITP), their platelets increased after splenectomy followed by the immediate increase of β-TG and PF4 above normal levels, suggesting the increase of absolute volume of intravascular destruction of plate-lets. In the recovery stage of disseminated intravascular coagulation (DIG), these proteins also increased parallel to the restoration of platelet count. In cases of neuroblastoma and a case of snake bite injury. platelet functions were accentuated by unknown mechanisms and β-TG :and PF4 concentrations also showed high levels in plasma. Although the cases are small in number in this study, it may be concluded that the measure-ment of β-TG and PF4 are useful in order to evaluate the abnormal platelet kinetics often observed in critically ill infant and children. Further investigation is neccessary whether the measurement of these proteins is valuable in early diagnosis of DIG.
