Application of a clinical decision rule and laboratory assays in pediatrics: Adult heparin-induced thrombocytopenia

Where have all the platelets gone? HIT, DIC, or something else?

Thrombocytopenia in ill children is common; accurately diagnosing the underlying etiology is challenging and essential for appropriate management. Triggers for accelerated consumption of platelets are numerous; common downstream mechanisms of clearance include platelet trapping in microvascular thrombi, phagocytosis, and platelet activation. Thrombocytopenia with microangiopathic hemolytic anemia (MAHA) is frequently due to disseminated intravascular coagulation. Thrombotic microangiopathy (TMA) is a subgroup of MAHA. Specific TMA syndromes include thrombotic thrombocytopenic purpura, complement-mediated TMA (CM-TMA), and Shiga toxin-mediated hemolytic uremic syndrome. Isolated thrombocytopenia is characteristic of immune thrombocytopenia; however, concomitant cytopenias are frequent in critically ill patients, making the diagnosis difficult. Immune thrombocytopenia with large vessel thrombosis is a feature of heparin-induced thrombocytopenia and antiphospholipid antibody syndrome. In addition, thrombocytopenia is common with macrophage activation, which is characteristic of hemophagocytic lymphohistiocytosis. While thrombocytopenia in ill patients can be driven by hypoproliferative processes such as myelosuppression and/or bone marrow failure, this review will focus on consumptive thrombocytopenia due to immune and nonimmune causes.

Heparin Induced Thrombocytopenia - Pathophysiology, Diagnosis and Treatment: A Narrative Review

Heparin-induced thrombocytopenia (HIT) is a life-threatening, immune-mediated complication following heparin exposure and is considered to be the most severe adverse reaction to heparin treatment that is not associated with bleeding. Development of autoantibodies against platelet factor 4 (PF4) - heparin complex constitutes the basis of the pathophysiological changes in patients suffering from HIT, which then binds to the surface of platelets and monocytes, thus provoking their activation and subsequent aggregation, ultimately leading to the formation of thrombosis. Formation of arterial and venous thrombosis is aggravated by the simultaneous activation of platelets and monocytes with a substantial mortality rate. The incidence of HIT is reported to be significantly lower in pediatric patients compared with adults. Diagnosis of HIT in pediatric population remains a clinical entity supplemented by laboratory evaluation. The positive predictive value of laboratory evaluation is further elevated by the use of scoring systems and predictive models used for hastening the diagnosis of HIT. Use of alternative anticoagulants like direct thrombin inhibitors and factor Xa inhibitors form the mainstay of treatment in cases of HIT, however, more prospective studies would be required in the pediatric population to delineate definitive guidelines for proper management of patients in this age-group. This article delivers diagnostic and treatment approach in case of patients with HIT, wherein the pathophysiology, clinical manifestations, diagnostic approach and the management of patients with HIT has been described.