Hematologic Emergencies ), and the clinical features of an underlying entity such as septic shock or extensive trauma, with which DIC is associated The increased red cell destruction in HUS and thrombotic thrombocytopenic purpura (TTP) is also caused by intravascular fibrin deposition Thrombocytopenia and uremia may lower the hemoglobin concentration even further via blood loss, impaired red cell production, shortened red cell survival, and increased plasma volume In some instances, anemia may be severe despite only mild uremia and absent thrombocytopenia, raising doubt about the diagnosis In more typical cases, however, the diagnosis is readily apparent from the findings of oliguria, central nervous system abnormalities, increased blood urea nitrogen, thrombocytopenia, and abnormalities of red cell morphology on peripheral blood smear, including fragments and helmet cells Another form of microangiopathic anemia involves the proliferation of blood vessels within a cavernous hemangioma that may trap red cells or initiate a localized consumptive coagulopathy, causing erythrocyte destruction Anemia in these cases is rarely severe unless the thrombocytopenia, which is more typical of the disorder, contributes to chronic blood loss Blood Loss Pallor resulting from sudden, massive hemorrhage is commonly secondary to trauma; it is usually accompanied by signs of hypovolemic shock and evidence of injury Patients may present in compensated or decompensated hypovolemic shock (see Chapter 10 Shock ) and need to be emergently managed Alternatively, the repeated loss of smaller amounts of blood over time may be associated with few findings other than pallor The finding of iron-deficiency anemia despite normal dietary iron intake or iron supplementation may be a clue to the presence of chronic blood loss from the gastrointestinal (GI) tract or less commonly within the lungs or urinary tract EVALUATION AND DECISION The initial assessment of the child with pallor should include an immediate determination of the severity of illness Rapid evaluation and intervention is imperative for the severely ill child In the presence of hypovolemic shock, immediate support of vascular volume is required When high-output cardiac failure from severe anemia occurs, transfusion with small aliquots of packed red cells is necessary After stabilization with initial therapeutic efforts, a thorough evaluation of the anemia can proceed If the child with pallor is not acutely ill, a deliberate search for the cause of pallor should be undertaken ( Fig 62.1 ) This may be accomplished by obtaining