Thrombocytopenia Flashcards
A platelet count of <100,000/μL generally defines (1). (2)
usually does not occur until counts are <50,000/μL .Platelet counts <20,000/μL are associated with
(3), and <10,000 with (4)
- thrombocytopenia 2. Hemorrhage from minor trauma 3. spontaneous (i.e. non traumatic) bleeding 4. risk of spontaneous intracerebral hemorrhage
Generally spontaneous bleeding involves ?
small blood vessels, skin, and mucosal membranes of the GI or GU tract
What are the general causes of thrombocytopenia?
- Decreased platelet production 2. Decreased platelet survival 3. Splenic sequestration 4. Dilution thrombocytopenia
Decreased platelet production is due to conditions affecting (1) production of platelets or those that directly affect (2) function
- marrow 2. megakaryocyte
Common causes of decreased platelet production include what drugs?
drugs such as alcohol, thiazide diuretics and cytotoxic chemotherapy agents
Bone marrow failure as in (1) causes severe thrombocytopenia as does replacement of bone marrow by tumor (2).
- aplastic anemia 2. leukemia or metastatic tumor involving bone marrow
Viral infections such as (1) directly infect (2) causing decreased platelet production.
- HIV and measles 2. megakaryocytes
Common causes of decreased platelet production include?
Drugs - etOH, thiazide diuretics, cytotoxic chemotherapy agents; Aplastic anemia; Leukemia; Metastatic tumor involving bone marrow; Viral infections - HIV, measles; Myelodysplasia; Vit B12 and folate deficiency
Decreased platelet survival may be due to what immune causes?
acute or chronic immune thrombocytopenia Infection or drug induced secondary autoimmune Autoimmune disease: SLE, B cell lymphoma, post-transfusion and neonatal isoimmune thrombocytopenia
(1) may induce secondary autoimmune thrombocytopenia as may certain infections (2)
- Quinidine, heparin, vancomycin and sulfa drugs 2. HIV and mononucleosis
Non immune mediated causes of decreased platelet survival include (1)
- DIC, the thrombotic microangiopathies like TTP and HUS
What conditions are associated with hypersplenism leading to splenic sequestration and thrombocytopenia?
liver disease portal hypertension CHF mononucleosis Myeloproliferative neoplasms Myelofibrosis
caused by (1) autoantibodies usually directed against (2). These autoantibodies are recognized by (3) receptors on (4) with destruction of the platelets occurring in the (5)
- IgG 2. platelet glycoproteins IIb‐IIIa 3. IgG Fc or opsonins 4. macrophages 5. spleen refers to ITP Chronic Immune Thrombo-cytopenia
Chronic ITP may be primary or secondary and associated with entities such as?
HIV; SLE; chronic lymphocytic leukemia
S/S of chronic ITP
skin or mucous membrane petechiae or ecchymosis; excessive menstrual bleeding; frequent nosebleeds; melena; *Head trauma in this patient can result in intracranial bleeding”
Treatment for chronic ITP
steroids or splenectomy
How is acute ITP different from chronic ITP?
Chronic ITP tends to affect women in their 40s, whereas acute ITP tends to affect children following a recent viral infection. Acute ITP is self-limiting, normally resolves within 6 months but 20% of cases progress to chronic ITP.
About 5% of patients on (1) experience a form of immune thrombocytopenia with many with serious consequences
- heparin
Heparin binds (1), resulting in a neo‐antigen that stimulates the production of antibody. This process induces (2) and results in (3)
- platelet factor 4 2. platelet activation 3. thrombosis and thrombocytopenia as platelets are consumed
How long does it take HIT to occur?
Generally platelet counts begin to drop 5‐10 days after heparin therapy is started.
All patients starting on heparin should have a (1) prior to initiation of heparin therapy.
- platelet count
A drop in platelet count of (1)% or more from baseline is highly suspicious for HIT and if noted, heparin must be discontinued and the patient placed on (2) (this greatly lowers the risk of HIT but does not completely eliminate it!).
- 50% 2. low molecular weight heparin
If HIT goes unrecognized and heparin therapy not stopped the patient may experience extensive arterial thrombotic episodes resulting in ?
vascular insufficiency to limbs, DVT and pulmonary thromboembolism
Other drugs such as (1) can bind platelet glycoproteins and induce an antibody response resulting in thrombocytopenia but not (2) as in HIT.
- quinine, quinidine and vancomycin 2. thrombosis
