Platelets

Question 1

Hemostasis

Answer 1

process by which bleeding stops (involved: blood vessels, platelets, plasma proteins - coag factors)

Question 2

Primary hemostasis

Answer 2

activation of platelets and forming the platelet plug

Question 3

Platelet plug

Answer 3

Platelet + vessel + von Willebrand Factor

Question 4

Primary hemostasis defects

Answer 4

petechia, ecchymoses, bleeding from mucosal sites (gingival bleeding, hematuria, epistaxis, GI Bleeding)

Question 5

Secondary Hemostasis

Answer 5

Coagulation cascade for the fibrin clot

Question 6

secondary hemostasis defects

Answer 6

hematoma, hemarthosis, hemoabdomen, hemothorax

much larger areas of hemorrhage!! more like bleeding into spaces.

Question 7

Platelet comes from

Answer 7

bone marrow - megakaryocyte (precursor)- platelet

Question 8

Thrombopoietin (TPO)

Answer 8

main stimulation for platelet production. Produced by the liver!
Levels of secretion seem constant.
Degraded by platelets if too much.
Inverse relationship between platelet mass and free TPO

Question 9

platelet lifespan/circulating concentration

Answer 9

6 days
Production, consumption (vasculitis), destruction (immune-mediated),
Redistribution (spleen)

Question 10

Response to blood vessel injury

Answer 10

1) exposure to sub endothelial collagen
2) VWF exposed and platelets adhere to it
3) platelet shape change
4) make and release signaling molecules to recruit more platelets and secondary hemostasis (ADP, TXA2)
5) form aggregation (hemostatic plus)

Question 11

Platelet evaluation

Answer 11

platelet concentration, platelet morphology, mean platelet volume (MPV), Plateletcrit (PCT - percent of volume of sample that is occupied by platelets), Bucal mucosal bleeding time (BMBT), Additional tests

Question 12

Platelet concentration

Answer 12

performed by analyzer (EDTA preferred)
Estimate based on smear (adequate or inadequate amount of platelets)
8-10 per 1000x field (dogs, cats, cattle)
5 per 1000x (horses)
Evaluate for platelet clumps
Hemorrhage from thrombocytopenia alone <25,000/microL

Question 13

KEY THING TO NOTE WHEN USING ANALYZER

Answer 13

know if there is clumping in platelets!!!!!!! it will give an inaccurate reading!

Question 14

large platelets (macroplatelets)

Answer 14

response to a thrombocytopenia ( weak evidence of bone marrow regeneration)
increased MPV

Question 15

Plateletcrit (PCT)

Answer 15

% of blood volume taken up by platelets
calculated from MPV and platelet concentration
Assessment of total circulating platelet mass

Question 16

Buccal mucosal bleeding time (BMBT)

Answer 16

Test platelet function (primary hemostasis - thrombopathias)
Sufficient platelet numbers (no thrombocytopenia) but have signs of primary hemostatic defects present
normal 1-3 minutes to stop bleeding

Question 17

Prolonged BMBT

Answer 17

> 4-5 minutes
inherited or acquired platelet function defect (thrombopathia)
- vWD, NSAIDS, Glanzmanns
- moderate to marked thrombocytopenia (SHOULD NOT BE PERFORMING BMBT TO BEGIN WITH)

Question 18

Thrombocytopenia (increased consumption/destruction)

Answer 18

Immune-mediated thrombocytopenia (ITP)

• common of marked
• <50,000/ microL
• Ab mediated destruction
• more primary than secondary
• if with IMHA (Evan’s Syndrome)

Question 19

Thrombocytopenia (vasculitis)

Answer 19

lead to prothrombotic state
due to 
- infection
- immune mediated
- mild to moderate thrombocytopenia

Question 20

T-penia (DIC)

Answer 20

• Systemic, uncontrolled activation
• ALWAYS secondary to underlying process
• mild to moderate decreases in platelets

Question 21

T-penia (Blood Loss)

Answer 21

• mild to moderate blood loss usually DOES NOT result in thrombocytopenia
• severe acute blood loss sometimes
• due to consumption as part of repeated attempts to stop bleeding

Question 22

T-penia (decreased production)

Answer 22

• Aplastic pancytopenia
• BM replacement or damage
• immune mediated destruction of megakaryocytic precursors
  
  • rare and Ab directed at them

Question 23

T-penia (abnormal distribution/ “sequestration”)

Answer 23

• splenic congestion/splenomegaly
  
  • pooling of platelets in spleen
  • splenomegaly
    RARE TO CAUSE

Question 24

T-penia (Multifactorial)

Answer 24

Neoplasia - decreased prod. or increased consumption
Infectious agents (erlichia, anaplasma): decreased prod. or increased consumption

Question 25

T-penia (inherited)

Answer 25

macrothrombocytopenia of CKCS
   - do not have abnormal bleeding
   - thrombocytopenia and macroplatelets
Calvier King Charles Spaniel 
- use PCT to assess platelet mass

Question 26

Macrothrombocytopenia

Answer 26

mutation in gene encoding beta-1 tubulin
seen in other breeds
Norfolk or Cairn Terriers

Question 27

What do you use for platelet mass assessment in inherited dz animals?

Answer 27

Plateletcrit (PCT)

Question 28

Thrombocytosis (increased production)

Answer 28

• inflammation
  
  • cytokines (IL-6) Stimulates TPO production
• iron deficiency
• Rebound thrombocytosis
• others

Question 29

Thrombocytosis (redistribution)

Answer 29

strenuous exercise and epinephrine - may result in mild

Question 30

Thrombocytosis (hemic neoplasia)

Answer 30

Primary (essential)
chronic myeloproliferative disorder of platelet precursors that result in large numbers of relatively normal platelets (RARE)

Question 31

Thrombopathy

Answer 31

Decreased platelet function
inherited and acquired causes
results: clinical bleeding in animal with normal platelets

Question 32

Thrombopathy (inherited)

Answer 32

vWD: most common hereditary disorder of dogs
have bleeding tendencies inspite of normal platelets
Dx: prolonged BMBT with normal platelets or vWF assay and multimetric analysis

Question 33

Thrombopathy (acquired)

Answer 33

variable degrees

secondary too: drugs, DIC, hepatic dz, hyperglobulinemia, uremia