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Platelet Disease
Hematology
| Question | Answer |
|---|---|
| Examples of platelet disease | Acute Thrombocytopenia; HIT; ITP; TTP; HUS |
| Causes of thrombocytopenia (decrease in plt numbers) | Decreased prodn (BM prob); inc destn (meds, immune mediated, DIC); Sequestration (Splenomegaly) |
| ITP diagnosis is: | one of exclusion (ie, notable for what is not present) |
| ITP findings | Neg FH/SH/PMH. Labs = acute thrombocytopenia; all else normal. Bruising, petechiae, gingival bleeding, hemorrhagic bullae in kids |
| ITP tx | Immunosuppression (prednisone 1mg/kg/day; rituximab; cyclophosphamide ). Immune modulation (IVIg, splenectomy). Stimulate platelet production (eltrombopag, romiplostin) |
| 2 types of HIT | 1: transient decrease. 2: immune mediated (significant) |
| HIT mechanism | Heparin combines w/PF4; this plus Abs -> platelet activation -> limb or life threatening thrombosis |
| HIT PMHx | On heparin 4-10 days; Inflammation/necrosis?; limb asymmetry? ; Cool/pulseless extremities? |
| HIT tx | Stop all heparin products (inc hep lines & flushes & LMWHs); prompt tx w/alt. anti-coagulation: Direct Thrombin Inhibitor (Argatroban, Lepirudin, Bivalirudin); Fondaparinux (synthetic anti-coagulant); warfarin after plt normal; w/alt anticoag; 6-12 wks |
| Increase in ultra-high molecular weight multimers of von Willebrand factor (2/2 deficiency vWF proteolytic enzyme) = | TTP |
| Effects of TTP | Intra-vascular platelet aggregation; systemic manifestations (CNS, Renal, Cardiac, Hematologic) |
| H&P for TTP | mental status changes; Sx/Sx related to end-organ damage and those of acute & idiopathic thrombocytopenia |
| TTP tx | Emergent large-volume plasma plasmapheresis; RBCs and fresh plasma returned to patient. Possible prednisone & antiplatelet tx |
| Platelet release involves: | Release of PF3 (Platelet factor 3); intracellular Ca (enhances further activation); thromboxane A2 |
| Adult ITP is usually: | chronic (as opposed to children, no viral infxn). |
| Most common drug causing ITP | Heparin |
| TTP clinical findings | Pentad: MAHA; thrombocytopenia; CNS abnormalities; fever; renal dysfunction |
| HUS: mental status changes? | No |
| HUS findings | Thrombocytopenia |
| Dx similar to TTP but without neuro symptoms | HUS |
| AutoAb to ADAMTS13 seen in: | TTP |
| HUS prognosis | Self-limiting in kids. 40% mortality in adults; CKD in 80% |
| Platelet aggregation abnormal with ristocetin, which corrects with the addition of normal platelets, in: | Bernard-Soulier Syndrome |
| HIT involves: | IgG antibody to Platelet Factor 4 |
| Confirm HIT with: | Serotonin Release Assay |
| Most common drug induced form of thrombocytopenia | HIT |
| HIT type I | Non-immune mediated: 100K platelets, no thrombosis (dc heparin) |
| HIT type II | Immune mediated: 30K platelets, thrombosis risk (require dc heparin, Rx direct thrombin inhibitors & warfarin) |
| HUS tx | D+ HUS: supportive; NO PLTS, NO ABX. Plasmapheresis & FFP |
| IgG antibody to PF4: seen in: | HIT (both art & venous thrombosis) |
| Microangiopathic hemolytic anemia & thrombocytopenia without an identifiable cause = | TTP (also often see neuro sxs) |
| anemia with schistocytes, thrombocytopenia & renal dysfunction in the absence of other causes of coagulopathy = | HUS |
| DIC vs HUS: dx | DIC low fibrinogen; HUS normal fibrinogen |
| Anagrelide may be used for: | P vera; thrombocytosis |
| Bleeding disorder clinical findings: platelet vs coagulopathy | plt: mucosa & skin; petechiae in low plt (NOT plt dysfn); coag: skin & mx; spont hemarthrosis in severe hemophilia |
| most common cause of abnormal bleeding: | thrombocytopenia |
| HUS vs TTP | HUS: no neuro sxs, more renal > TTP |
| Causes of decreased platelet function: membrane defects | Glanzmann Thrombasthenia; Bernard-Soulier |
| Causes of decreased platelet function: Pathway Defects | Arachidonic Pathway Defect |
| Causes of decreased platelet function: medications | Aspirin/Clopidogrel use |
| Causes of decreased platelet function: acquired disease | MDS |
| Diseases causing ITP | SLE, CLL, virus (HIV/Hep C) |
| von W defect is in: | platelet adhesion only |
| HIT occurs when? | 4-10 days post heparin infusion |
| Adult ITP epidemiology | Peak = 20-50 y.o. (2-4 yo in kids). F:M = 2:1 |
| ITP etiology | Acquired autoimmune. Isolated thrombocytopenia. Autoantibody binds to platelet membrane antigen -> bound to splenic macrophages & destroyed in spleen -> low platelets 2/2 splenic sequestration & accelerated platelet destruction |
Created by:
Abarnard
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