thrombocytopenia

Question 1

thrombocytes

Answer 1

• aka platelets
• required for clotting
• precursor cells= megakaryocytes
• life span of 5-9 days

Question 2

what stimulates thrombocyte production

Answer 2

• thrombopoietin

- produced by liver and kidneys

Question 3

where are excess platelets stored

Answer 3

• spleen

Question 4

normal platelet levels

Answer 4

• 150K- 400k

Question 5

platelet level with post op bleed risk

Answer 5

• < 50k

Question 6

platelet level with spontaneous bleed risk

Answer 6

• 10k- 20k

Question 7

heparin induced thrombocytopenia (HIT)

Answer 7

• 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

Question 8

types of HIT

Answer 8

• HIT type 1

- HIT type 2

Question 9

HIT type 1

Answer 9

• nonimmune
• dt direct effect of heparin on platelets
• causes decreased count in 48 hours
• will normalize

Question 10

HIT type 2

Answer 10

• IgGmediated

- increased risk of prothrombotic complications: limb ischemia, CVA, MI, DVT/PE

Question 11

dx of HIT

Answer 11

• assess “four T’s”

- confirm dx with PF4 heparin ELISA testing

Question 12

tx of HIT

Answer 12

• 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

Question 13

what to do for a pt with hx of HIT

Answer 13

• not a risk of forming heparin ab with re-exposure

- ok to reintroduce after 100 days

Question 14

what is the most common inherited bleeding disorder

Answer 14

• von willebrand disease

Question 15

what is the normal role of vWF

Answer 15

• mediates platelet adhesion at site of vascular injury

- protects FVIII from degredation

Question 16

type 1 vW disease

Answer 16

• make less vWF
• asx or mild sx
• most comon type

Question 17

type 2 vW dsiease

Answer 17

• make vWF but less effective
• mod-severe bleeding
• dx in childhood

Question 18

type 3 vW disease

Answer 18

• complete absence of vWF
• low levels of FVIII
• most severe form
• rare

Question 19

dx of vW disease

Answer 19

• measure amount and functionality of vWF

- measure FVIII levels

Question 20

tx of vW disease

Answer 20

• 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

Question 21

idiopathic thrombocytopenia purpura (ITP)

Answer 21

• isolated thrombocytopenia
• normal BM
• dx of exclusion
• may be assoc with SLE, hep c, HIV

Question 22

pathophys of ITP

Answer 22

• IgG directed at platelet surface antigens and megakaryoctes
• reduced lev of thrombopoietin

Question 23

si/sx of ITP

Answer 23

• isolated thrombocytopenia
• normal BM bx
• Ab only seen in 60% of pts
• purpuric rash
• increased tendency to bleed
• rarely have spont/ severe hemorrhage

Question 24

tx of ITP

Answer 24

• only indicated if count < 20-30k or severe hemorrhage
• first line: IV steroids
• second line: IVIG
• platelet transfusion if severe hemorrhage

Question 25

thrombotic thrombocytopenia purpura (TTP)

Answer 25

• 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

Question 26

pentad of TTP

Answer 26

• thrombocytopenia
• microangiopathic hemolytic anemia
• neuro sx
• renal failure
• fever

Question 27

tx of TTP

Answer 27

• first line: plasmapheresis
• refractor/ relapsing: immunosuppressives
• transfusion C/I d/t increased clot risk
• only give FFP in plasmapheresis

Question 28

how do you monitor TTP

Answer 28

• LDH
• platelets
• schistocytes