HEMATOLOGY - platelet disorders + TRA Flashcards
EXAM 2 content
what are thrombocytes? what can they do?
thrombocytes = platelets
- irregularly shaped anuclear cytoplasmic fragments = not true cells
- needed for blood coagulation + control bleeding
- an injury to a blood vessel –> plates release adhesive proteins, coagulation & growth factors
- plates can assume different shapes + form extensions –> increase surface area & plug vascular openings to control bleeding – main component in primary hemostasis
what is the normal thrombocyte concentration in the blood?
150,000 - 400,000 platelets/mm3
- 1/3 platelets are pulled into spleen
what is thrombocytopenia? what kinds of risks can happen with lower level of plates?
thrombocytopenia = low plate count
- < 150,00 plates
- < 50,000 –> risk of hemorrhage w minor trauma
- 10,000 - 15,000 –> risk of spontaneous bleeding w/o trauma (mucous membranes like gums + nose bleeding, petechiae, ecchymosis, purpara)
- < 10,000 –> risk of severe spontaneous bleeding (fatal on GI, resp, or CNS)
what are the threshold for platelet transfusions?
- actively bleeding = transfused to keep plate counts of 50,000+ plates
- pt w/ thrombocytopenia needs surgery = transfused prior, increased to at least 50,000
- pts w/ below 10,000 –> transfused to prevent spontaneous bleeding
what is petechiae, ecchymosis, & purpura?
- petechiae = pinpoint round spots on skin bc of bleeding
- ecchymosis = bruising (escaped blood from tissues or ruptured blood vessels)
- purpura = patches of purple discoloration (from blood into skin + mucous membranes)
what are causes of thrombocytopenia, decreased platelet production?
- viruses: EBV, rubella, CMV, HIV
- drugs: thiazides, estrogens, quinine-containing drugs, chemo agents, ethanol
- nutritional deficiencies: vit b12 or folic acid
- chronic renal failure
- cancer
what are causes of thrombocytopenia, increased plate consumption? (these are what are are focusing on)
- heparin induced thrombocytopenia (HIT)
-immune thrombocytopenia purpura (ITP) - thrombotic thrombocytopenic purpura (TTP)
- disseminated intravascular coagulation (DIC)
what is heparin induced thrombocytopenia (a type of increased plate consumption)? cause? character? diagnosis? treatment?
a immune mediated reaction to heparin (unfraction or low molecular weight)
- results from: forming antiplatelet antibodies (plate activation + consumption)
- characterized by: precipitous drop in platelet count + venous/arterial thrombosis might occur bc of prothrombotic state
- diagnosis: blood test for anti-heparin platelet factor 4 antibodies
treatment:
- stop all forms of heparin, never give again –> check allergy list
- give direct thrombin inhibitors (ARGARTROBAN) – another anticoagulant
what is immune thrombocytopenia purpura (a type of increased plate consumption)? cause? manifestations? treatment?
- acute: antigen forms immune complexes with circulating antibody –> bind to receptors on plates –> destruction in spleen
- chronic: IgG autoantibodies against plate specific antigens – autoantibodies bind to platelet antigens –> antibody coated platelets removed from blood by macrophages in spleen
- clinical manifestations: petechiae, purpura, epistaxis & risk of severe bleeding
treatment:
- glucocorticoids: suppress immune responses & prevent sequestering + further destruction of spleen
- intravenous immune globulin (IVIG): increases plate count by interfering with phagocytosis of antibody coated platelets by macrophages (for chronic)
- splenectomy: plates are in or by the spleen
what are the drugs that can be a treatment for ITP (immune thrombocytopenia purpura)? what is the over class? which one is the exemplary? what do they do?
Thrombopoietin Receptor Agonists (TRAs) – stimulate production of platelets
- ROMIPLOSTIM (Nplate) – exemplary
- AVATROMBOPAG (Doptelet)
- ELTROMBOPAG (Promacta)
what is the mechanism of action of ROMIPLOSTIM?
ROMIPLOSTIM is a peptibody (combo of peptide & antibody) –> mimics thrombopoietin –> stimulates megakaryocytes – cells that become platelets
what are the therapeutic uses of ROMIPLOSTIM?
only AFTER traditional ITP treatments have failed
what are the adverse effects of ROMIPLOSTIM?
- arthralgia, dizziness, insomnia, pain in extremities, abdominal pain, myalgia, shoulder pain, dyspepsia, & paraesthesias
uncommon but serious:
- bone marrow fibrosis = bone forming cells replaced by fibrotic tissue
- hematologic malignancy – from stimulation of bone marrow cells
- thrombotic/thromboembolic complications – from excessive platelet production
what are the contraindications/precautions when taking ROMIPLOSTIM?
platelet count may drop to pretreatment levels when drug is discontinued
how do we administer ROMIPLOSTIM?
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