thrombocytopenia Flashcards
thrombocytes
- aka platelets
- required for clotting
- precursor cells= megakaryocytes
- life span of 5-9 days
what stimulates thrombocyte production
- thrombopoietin
- produced by liver and kidneys
where are excess platelets stored
- spleen
normal platelet levels
- 150K- 400k
platelet level with post op bleed risk
- < 50k
platelet level with spontaneous bleed risk
- 10k- 20k
heparin induced thrombocytopenia (HIT)
- IgG ab to heparin- platelet factor 4
- binds to platelets and inactivates them
- causes thrombocytopenia and prothrombotic states
- consider whenever drop in platelets after heparin exposure
types of HIT
- HIT type 1
- HIT type 2
HIT type 1
- nonimmune
- dt direct effect of heparin on platelets
- causes decreased count in 48 hours
- will normalize
HIT type 2
- IgGmediated
- increased risk of prothrombotic complications: limb ischemia, CVA, MI, DVT/PE
dx of HIT
- assess “four T’s”
- confirm dx with PF4 heparin ELISA testing
tx of HIT
- DO NOT hold tx for lab confirmation
- d/c all heparin products
- argatroban until platelets 150k then bridge to warfarin
- LENI eval for DVT risk
what to do for a pt with hx of HIT
- not a risk of forming heparin ab with re-exposure
- ok to reintroduce after 100 days
what is the most common inherited bleeding disorder
- von willebrand disease
what is the normal role of vWF
- mediates platelet adhesion at site of vascular injury
- protects FVIII from degredation
type 1 vW disease
- make less vWF
- asx or mild sx
- most comon type
type 2 vW dsiease
- make vWF but less effective
- mod-severe bleeding
- dx in childhood
type 3 vW disease
- complete absence of vWF
- low levels of FVIII
- most severe form
- rare
dx of vW disease
- measure amount and functionality of vWF
- measure FVIII levels
tx of vW disease
- desmopressin in 1 and 2 -> increased relase of vWF and FVIII
- transfusion for type 3
- FVIII if severe bleeding or as ppx before major surgery
idiopathic thrombocytopenia purpura (ITP)
- isolated thrombocytopenia
- normal BM
- dx of exclusion
- may be assoc with SLE, hep c, HIV
pathophys of ITP
- IgG directed at platelet surface antigens and megakaryoctes
- reduced lev of thrombopoietin
si/sx of ITP
- isolated thrombocytopenia
- normal BM bx
- Ab only seen in 60% of pts
- purpuric rash
- increased tendency to bleed
- rarely have spont/ severe hemorrhage
tx of ITP
- only indicated if count < 20-30k or severe hemorrhage
- first line: IV steroids
- second line: IVIG
- platelet transfusion if severe hemorrhage
thrombotic thrombocytopenia purpura (TTP)
- normally ADAMSTS13 cleaves vWF to smaller pieces
- in TTP have faulty ADAMSTS13 or inhibited by Ab -> improper cleavage -> aggregation and microthrombi formation
- RBCs get damaged by microthrombo -> intravasc hemolysis and schistocytes -> ischemia
pentad of TTP
- thrombocytopenia
- microangiopathic hemolytic anemia
- neuro sx
- renal failure
- fever
tx of TTP
- first line: plasmapheresis
- refractor/ relapsing: immunosuppressives
- transfusion C/I d/t increased clot risk
- only give FFP in plasmapheresis
how do you monitor TTP
- LDH
- platelets
- schistocytes
