Platelets

Question 1

Platelets

Answer 1

Initial hemostatic plug
Temporary

Question 2

Coagulation proteins

Answer 2

Reinforce the platelet framework and part of definitive hemostatic plug

Question 3

What is the precursor cell to platelets

Answer 3

Megakaryocyte, cytoplasmic fragments

Question 4

How are platelets released in blood

Answer 4

Megakaryocyte in bone marrow and reach out branches into the blood vessel and the sheer flow of blood will cause portions of the cytoplasm to break off

Question 5

Platelet regulation

Answer 5

Thrombopoietin from the liver at a constant rate and removed from blood by circulating platelets. If platelet mass reduces there is an increase in TPO concentration resulting in increased production. Inflammatory cytokines also increase production

Question 6

Thrombopathia

Answer 6

Qualitative disorder of platelets

Question 7

Extrinsic platelet disorder

Answer 7

Platelets are normal but there is some other part of the way the platelets work is not. IE von Willebrand factor missing

Question 8

Intrinsic platelet disorder

Answer 8

Platelets are abnormal

Question 9

4 categories of platelet disorders

Answer 9

1. Congenital for abnormal conc
2. Acquired causes for abnormal conc, most common
3. Congenital functional defect
4. Acquired functional defect

Question 10

Platelet type bleeding from thrombocytopenia or thrombopathia

Answer 10

Bleeding from mucosal surfaces including: epistaxis, gingival, UT, and GI bleeding. See petechial or ecchymotic hemorrhage on any skin or mucosal surface

Question 11

At what point can you get spontaneous bleeding due to low platelet conc?

Answer 11

<50,000platelets/ul

Question 12

Mean platelet volume

Answer 12

MPV from automated platelet concentration.
Average size of circulating platelets

Question 13

High MPV with thrombocytopenia

Answer 13

Megakaryocytes are trying to respond to low platelet numbers. Not you and will stay that big. Good sign

Question 14

Low MPV with thrombocytopenia

Answer 14

May indicate insufficient number of megakaryocyte present or failure to response

Question 15

Normal MPV in thrombocytopenia

Answer 15

Megakaryocytes not responding or it is too early for response

Question 16

When do we test platelet function

Answer 16

When the concentration is adequate but have platelet type bleed

Question 17

Buccal mucosal bleeding time

Answer 17

Indicate primary hemostasis or platelet status. Only use on pt with adequate platelet concentrations. Can’t be used to detect coagulopathies

Question 18

Clot retraction

Answer 18

Test platelet function and do not do on pt with medications that affect clotting. Tests to see if blood mixed with thrombin will form a clot retraction. Always do duplicates and with control

Question 19

Platelet aggregometry

Answer 19

Gold standard. Highly specialized and not readily available and must be completed quickly

Question 20

Cats and platelets

Answer 20

-Tend to be more clumped (reactive)
-Variable size
-See more giant platelets
-Do not use impedance hematology analyzers
-Often have no clinical signs of thrombocytopenia

Question 21

Inherited macrothrombocytopenia signalment

Answer 21

Cavalier King Charles are poster child

Question 22

Inherited macrothrombocytopenia

Answer 22

Low number but larger so there is no clinical bleeding

Question 23

Immune mediated thrombocytopenia

Answer 23

Circulating platelets or megakaryocytes destroyed by immune mediated mechanism

Question 24

Causes of ItP

Answer 24

1. Primary or autoimmune
2. Secondary to immune complex absorption or neoantigen expression
3. Incompatible transfusion

Question 25

Rickettsial induced thrombocytopenia

Answer 25

-Erlichia canis
-Anaplasma platys and phagocytum
-Rickettsia rickettsia
Have immune mediated clearance and decreased lifespan as well as vasculitis induced consumption

Question 26

Drug induced thrombocytopenia

Answer 26

-Primary-> destroyed by drug interaction
-Secondary immune mediated-> drug dependent (if you stop drug and stops reaction to platelets) or independent
-Secondary bone marrow suppression

Question 27

DIC

Answer 27

Pathologic process characterized by widespread activation of clotting cascade and get clots throughout body and use up all the platelets. See if there is massive tissue damage

Question 28

Destruction or crowding of marrow cavity thrombocytopenia

Answer 28

Inflammatory disease
Myeloproliferative disease
Myelopthsis/myelofibrosis

Question 29

Von Willebrand disease

Answer 29

Most common congenital extrinsic platelet function disorder in dogs. Decreased VW factor reduces platelet adhesion

Question 30

Diagnosis of von Willebrand

Answer 30

ELISA to determine antigen levels using plasma not serum
Clot retraction and APTT is normal

Question 31

Diagnosis of von Willebrand

Answer 31

ELISA to determine antigen levels using plasma not serum (EDTA or citrated plasma)
DNA test is available
Clot retraction and APTT is normal

Question 32

Glanzmann Thrombasthenia

Answer 32

Congenital intrinsic platelet dysfunction. No clot retractions. Defect in GpIIb-IIIa so abnormal fibrinogen binding and unable to aggregate platelets

Question 33

CalDAG-GEFI Thrombopathia

Answer 33

Congenital intrinsic platelet dysfunction. Abnormal signal transduction so decreased binding of platelets to fibrinogen. Normal clot retraction

Question 34

Acquired Qualitative Platelet Function disorders

Answer 34

-FeLV
-Drug induced (TXA2)