Aspects of bleeding complications and hemostasis at central line insertion and mild induced hypothermia

Sammanfattning: Bleeding complications range from 0.5 to 1.6% in connection with central venous catheter insertions but are more frequent in patients with bone marrow failure and severe thrombocytopenia. Although supportive evidence is scarce, prophylactic platelet transfusion is sometimes performed in these patients before catheter insertion. Furthermore, the ideal threshold platelet count and timing of transfusion remain controversial among clinical studies. Hypothermia is generally considered to reduce coagulation and platelet function. However, studies performed in animals, healthy volunteers, and patients have shown conflicting results. Paper I, a retrospective study in non-intensive care unit patients, showed that serious bleeding complications in association with central line insertions were uncommon and that insertion of a large bore catheter may be an independent risk factor for mild bleeding complications in this population. Paper II, a prospective observational study, evaluated the efficacy of prophylactic platelet transfusions in thrombocytopenic patients with bone marrow failure. Transfusion improved hemostatic parameters in ROTEM and Multiplate tests by increasing the number of platelets and not by enhancing platelet function. Improved clotting parameters persisted between 1 and 4 hours after transfusion. Paper III demonstrated increased platelet aggregation and strengthened clot formation over time in out-of-hospital cardiac arrest patients treated with hypothermia. In patients with dual platelet inhibition, including ticagrelor and aspirin, this effect was offset by powerful P2Y12 blockade, confirmed by analysis of vasodilator-stimulated phosphoprotein. The effect of ticagrelor was delayed in survivors of cardiac arrest, probably due to slow gastric emptying. Paper IV demonstrated prolonged clot initiation and decreased clot propagation in ROTEM testing (EXTEM, FIBTEM, and APTEM assays) in whole blood from out-of-hospital cardiac arrest patients treated with mild induced hypothermia. Paper V investigated whole blood from acute coronary syndrome patients treated with ticagrelor and aspirin. In vitro applied hypothermia to 33 degrees C markedly increased platelet activity measured by flow cytometry, whereas a viscoelastic coagulation test (Sonoclot) revealed a hypocoagulative response.