Hemostasis 1

Question 1

define hemostasis - response to, what components are involved, what is outcome

Answer 1

response to vascular injury, interactive process between BVs, platelets, coat proteins, and fibrinolytic system; leads to formation and resolution of hemostatic plug to stop bleeding

Question 2

describe 5 basic steps of hemostasis

Answer 2

vascular injury, vasospasm/vasoconstriction, platelet plug formation (primary hemostasis), coagulation (secondary hemostasis), clot retraction and fibrinolysis

Question 3

what are platelets and what is lifespan

Answer 3

nucleate cytoplasmic fragments from megakaryocytic in bone marrow, 4-6 days in circulation

Question 4

production of platelets can be dramatically produced in presence of

Answer 4

thrombopoeitin

Question 5

what causes platelet activation and what happens to a platelet when activated

Answer 5

exposure to sub endothelial collaged and adhesive protein vWF leads to platelet adhesion and activation. shape change from disc to sphere and develops projections.

Question 6

describe steps of primary hemostasis after an injured blood vessel occurs

Answer 6

1. Endothelin release causes vascular constriction within minutes of injury.
2. vWF (von Willebrand factor) is present on the subendothelium of injured vessels and acts as a tether for platelets.
   
   • NOTE: vWF is esp important for vessels with high blood flow.
3. Exposure to subendothelial collagen and vWF leads to platelets ADHERING to wall and becoming ACTIVATED.
   
   • Once activated, they change shape from disk to sphere and develop projections.
4. Activate platelets release GRANULES, RECRUIT others to site of injury, and AGGREGATE to form a HEMOSTATIC PLUG.
   Surface for firbirn formation and leukocytes are binding also.

Question 7

clinical signs of hemostasis

Answer 7

petechia 1-2 mm, purpura 3mm-2cm, ecchymosis 2-3 cm; persistent oozing from incisions or skin, epistaxis, melon, hematochezia, hematuria

Question 8

2 types of platelet disorders (primary hemostasis disorders)

Answer 8

thrombocytopenia = decreased platelet numbers (acquired or congenital); thrombopathia = platelet dysfunction disorder (again, acquired or congenital)

Question 9

if you see less than 2-3 platelets/hpf what do you do

Answer 9

consistent with thrombocytopenia, investigate for clinical hemorrhage

Question 10

name 3 mechanisms of acquired thrombocytopathia

Answer 10

increased platelet destruction, increased platelet consumptions, or decreased platelet production

Question 11

name a congenital thrombocytopenia, what is it in dogs

Answer 11

inherited macrothrombocytopenia; Cavalier King Charles Spaniel

Question 12

what are 2 causes of increased platelet destruction in acquired thrombocytopenia

Answer 12

primary (idiopathic) or secondary immune mediated thombocytopenia, IMT

Question 13

what are 2 causes of increased platelet consumption in acquired thrombocytopenia

Answer 13

DIC, thrombosis

Question 14

what are 3 causes of decreased platelet production in acquired thrombocytopenia

Answer 14

infiltrative bone marrow disease (myelophthisis) or myelofibrosis, drug induced, viral induced

Question 15

describe clin path change seen with primary (idiopathic) IMT, why is this happening, how is it diagnosed

Answer 15

severe platelet number drop, due to Abs being generated in response to target self antigen on platelets and potentially megakaryocytic as well, this is a diagnosis of exclusion

Question 16

describe clin path change seen with secondary IMT, why is this happening

Answer 16

as with primary IMT, see a severe platelet number drop; occurs with formation of immune complexes on platelet surfaces and can be associated with vaccines, drugs, rickettsial disease, viral disease, or neoplasia

Question 17

what effect does intravascular coagulation (localized or DIC) have on platelets

Answer 17

the increased clotting depleted platelets (and clotting factors). vasculitis can also damage endothelial cells, exposing sub endothelium so platelets will adhere and activate

Question 18

3 most common causes of severe thrombocytopenia are

Answer 18

primary or secondary IMT, drug induced, and decreased platelet production (neoplasia, fibrosis) ***

Question 19

define myelophthisis. what is clin path finding seen?

Answer 19

replacement normal hematopoietic tissue with normal tissue (eg. neoplasia); leads to severe drop in platelet numbers, like IMT

Question 20

define myelofibrosis

Answer 20

replacement of normal hematopoietic tissue with fibrous tissue

Question 21

name at least 2 and at least 2 viruses that decrease platelet production; what is mechanism

Answer 21

estrogen, griseofulvin, cyclophosphamide, chloramphenicol suppress bone marrow. FeLV, FIV, Parvo, distemper, EIA, BVD destroy directly or indirectly platelets and potentially MKs

Question 22

characteristic findings and C/S inherited macrothrombocytopenia

Answer 22

large platelets and decreased platelet numbers; thrombocytopenia persistent and no C/S; not associated with hemorrhage

Question 23

breeds affected by inherited macrothrombocytopenia (a congenital thrombocytopenia)

Answer 23

CKCS! Chihuahuas, lab retrievers, poodles, shih tzus, maltese, jack russels

Question 24

name the most common hereditary bleeding disorder in dogs, pigs, and people. is it extrinsic or intrinsic?

Answer 24

von Willebrands disease vWD. [this is an extrinsic disorder of platelet dysfunction, and an inherited thrombopathia (platelet disorder)]

Question 25

what is cause of vWD.

Answer 25

extrinsic disorder of platelet dysfunction that is caused by a deficiency in vWF. (vWF is a tether for platelets to sxbendothelial collagen at site of vessel injury and is important in vessels with high shear stress, ie. the small vessels)

Question 26

species vWD is common in? rare in?

Answer 26

dog pig people. rare in cat horse cattle

Question 27

there are 3 types of vWD reported in dogs. describe type 1: how common? how severe? breeds?

Answer 27

type 1, most common over 95% cases, variable severity. LOW vWF protein but NORMAL strx and fxn, many breeds eg. Doberman pinschers.

Question 28

there are 3 types of vWD reported in dogs. describe type 2: how common? how severe? breeds?

Answer 28

LOW numbers vWF proteins and ABNORMAL strx and fin, severe but rare. German shorthaired and wire-haired pointers

Question 29

there are 3 types of vWD reported in dogs. describe type 3: how common? how severe? breeds?

Answer 29

markedly reduced to absent vWF protein. severe but rare. Chesapeake bay retrievers, Scottish terriers, shetland sheepdogs and others.

Question 30

what should you look at in your blood tests for primary hemostasis? include CBC and morphology and tube type.

Answer 30

blood smear look for giant placements and platelet clumps (which are normal in monolayer). EDTA purple top is best. thrombocytopenia will be under 50 x 10^9 platelets/L on our CBC with platelet count

Question 31

what clinical test should you perform for primary hemostasis (except in cases of thrombocytopenia)? what does it evaluate, what is normal range, what should you consider if prolonged

Answer 31

buccal mucosal bleeding time, usually <4 min, if prolonged consider thrombopathia likely vWD. evaluates platelet function WHEN NORMAL PLATELET NUMBERS. if you have thrombocytopenia–>don’t perform, test will likely be prolonged.

Question 32

what test might you perform to differentiate between IMT and myeloproliferative disease, for primary hemostasis

Answer 32

bone marrow aspirate

Question 33

you suspect vWF disease because of a mild to severe bleeding tendency, prolonged BMBT (a fairly insensitive test) and normal platelet numbers. what test can you perform for vWF deficiency or vWD? what range would you expect? what sample should you use?

Answer 33

vWF antigen assay, vWF:Ag. vWF:Ag <50% considered decreased and a carrier of vWF trait, and you would expect <25% in bleeding dogs, often <15%. use EDTA or citrated plasma sample.

Question 34

an 8 y/o Staffy has been mildly lethargic, has petechial hemorrhages in his mucus membrane, and biochemistry results are WNL. his bloodwork shows slight polychromatic, occasional nRBCs, mild leukocytosis monocytosis, neutrophilia, and thrombocytopenia. what is going on?

Answer 34

leukogram–could be inflammation of stress component.