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Thrombocytopenia in the ICU

About Platelets. Normal count ranges from 150 to 450k/ulProduced by megakaryocytes, about 30 to 50k/ul per dayProduction can be increased 8x during stressYoung platelets have much greater functionAverage platelet survival is 8-10 daysUp to 1/3 of platelets reside in spleen but this can be much higher in splenomegaly..

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Thrombocytopenia in the ICU

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    1. Thrombocytopenia in the ICU Matthew Volk Morning Report 4/6/2009

    2. About Platelets Normal count ranges from 150 to 450k/ul Produced by megakaryocytes, about 30 to 50k/ul per day Production can be increased 8x during stress Young platelets have much greater function Average platelet survival is 8-10 days Up to 1/3 of platelets reside in spleen but this can be much higher in splenomegaly.

    3. Thrombocytopenia Strictly defined as a platelet count of <150k/ul Distinguish from Defective platelet function (eg: Bernard-Soulier, aspirin usage, and uremia) Clotting factor deficiency (eg: hemophilia) Symptoms include petichiae, purpura, conjunctival hemorrhage, mucocutaneous bleeding

    4. Differential Diagnosis Decreased Production Marrow dz: Aplastic anemia, infiltration Production impairment: drugs, HIV Poor maturation Decreased Survival Immunologic destruction ITP, HIT, drug, infxn Nonimmune destruction DIC, TTP/HUS Sequestration splenomegaly (liver dz) Dilutional severe bleeding

    5. Differential Diagnosis Thrombocytopenia in Primary Care Most common: platelet clumping, wrong patient, or chronic ITP Need to r/o HIV and occult liver disease In pregnancy ?gestational thrombocytopenia In those age >60 ?myelodysplastic disorder May be congenital in those with longstanding thrombocytopenia

    6. Differential Diagnosis Thrombocytopenia in the ICU is usually 2/2 to an underlying medical condition: Sepsis 52% DIC 25% Drug Induced 10% Blood loss 8% HIT 1% Hematologic Malignancy - excluded

    7. Heparin-Induced Thrombocytopenia (HIT) Up to 5% chance with UFH, 1% with LMWH Can occur with heparin flushes, catheters Distinguish types of HIT Type 1 rapid onset, clinically insignificant Type 2 onset in 5-14 days, severe thrombosis Verify HIT 2 with PF4 antibody test Anticoagulate with Lepirudin, Argatroban, or bivalirudin (direct thrombin inhibitors) Avoid coumadin and platelet transfusion until platelet recovery

    8. Disseminated Intravascular Coagulation (DIC) Caused by an overwhelming release of tissue factor (infxn, trauma, obstretrics) DIC score calculated with platelet count, Pt, d-dimer (rises), and fibrinogen (falls). Also, AT3 level falls. Can replete with platelets, FFP, cryo (if low fibrinogen), or even AT3 concentrate.

    9. Thrombotic Thrombocytopenic Purpura (TTP) Etiology thought to be diffuse endothelial damage Pentad of fever, AMS, ARF, low platelets, and MAHA Diagnose with schistocytes at least 2-5 per high power field Therapy is plasmapheresis Platelet transfusion contraindicated

    10. Hematologic Malignancy - Lymphoma Bone marrow involvement can vary from <5% to >95% of cases, depending upon lymphoma type. Extranodal NK/T-cell lymphoma typically less than 5% involvement Thrombocytopenia can be present in as many as 70% of aggressive cases

    11. Diagnostic Approach

    12. Diagnostic Approach

    13. Platelet Transfusions Generally accepted parameters >10k/ul to prevent spontaneous bleeding, in particular devastating ICH Three studies show no difference between the 20k and 10k threshold, and 25% reduction in platelet transfusion. >50k/ul for procedures Recent review, however, recommended against transfusion certainly for central lines; possibly even for liver bxs, and LPs.

    14. References Arepally GM et al. Clinical Practice, Heparin Induced thromboctyopenia. N Engl J Med. 2006 Aug 24;355(8):809-17. Contran RS et al. Robbins Pathologic Basis of Disease 6th ed. Saunders: Philadelphia. 1999. Dogan A. Bone marrow histopathology in peripheral T-cell lymphomas. Br J Haematol. 2004 Oct;127(2):140-54. George JN. Evaluation and management of thrombocytopenia by primary care physicians. Uptodate Online. Heal JM, Blumberg N. Optimizing platelet transfusion therapy. Blood Rev. 2004 Sep;18(3):149-65. Landaw SA et al. Approach to the adult patient with thrombocytopenia. Uptodate Online. Levi M et al. Coagulation abnormalities in critically ill patients. Critical Care 2006, 10:222. Marino PL, The ICU Book 3rd edition. Lippincott Williams & Wilkins: Philadelphia. 2007. Win-yan A et al. Clinical differences between nasal and extra-nasal NK/T-cell lymphoma. Blood. Prepublished online Nov 24, 2008.

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