hemostasis and coagulation Flashcards
1
Q
ecchymoses
A
superficial hemorrhage of about 1cm in diameter
2
Q
epistaxis
A
bleeding from the nares
3
Q
hematoma
A
localized collection of blood, usually clotted, in an organ, space, or tissue
4
Q
petechia
A
pinpoint bleeding where tiny red spots are seen on mm due to the escape of small amounts of blood
5
Q
plasmin
A
aka fibrinolysin
- an enzyme that dissolves the fibrin of blood clots
6
Q
plasminogen
A
the inactive precursor to plasma that is found in body fluids and plasma
7
Q
prothrombin
A
a plasma protein involved in blood coagulation that, on activation by factors in the plasma including calcium, is converted to the enzyme thrombin
8
Q
what is thrombin converted from?
A
prothrombin
9
Q
purpura
A
- bruising
10
Q
scab
A
a blood clot that forms on the skin surface and fries
11
Q
thrombin
A
- an enzyme of the blood plasma that, in the presence of calcium, catalyses the conversion of fibrinogen to fibrin
12
Q
what is needed for thrombin to catalyze the conversion of fibrinogen into fibrin?
A
calcium
13
Q
what does thrombin catalyze the conversion of?
A
fibrinogen to fibrin
14
Q
thromboplastin
A
- an enzyme released from platelets that converts prothrombin to thrombin as blood starts to clot
15
Q
what helps convert prothrombin into thrombin as blood starts to clot?
A
thromboplastin
16
Q
thrombus
A
- a blood clot formed within a vessel that remains at the site of formation
- if it detaches into the bloodstream it becomes a thromboembolus causing a blockage in the vessel and causing heart attacks and strokes
17
Q
which coagulation factors are produced by the endothelium?
A
- Vlll
- antihemophilic factor, thromboplastinogen, von willebrand
18
Q
which coagulation factors are dependent on vitamin K?
A
ll
Vll
lX
X
19
Q
coagulation factor l
A
- synonym: fibrinogen
- produced by: liver
20
Q
coagulation factor ll
A
- sysnonym: prothrombin
- produced by: liver
- dependent on: vitamin K
21
Q
coagulation factor lll
A
- synonym: tissue thromboplastin
- produced by: liver
22
Q
coagulation factor lV
A
- synonym: calcium
- produced by: liver
23
Q
coagulation factor V
A
- synonym: labial factor, proaccelerin
- produced by: liver
24
Q
coagulation factor Vl
A
- unassigned
- produced by: liver
25
coagulation factor Vll
- synonym: proconvertin, stable factor
- produced by: liver
- dependent on: vitamin k
26
coagulation factor Vlll
- synonym: antihemophilic factor (AHF), thromboplasinogen, von willebrand
- produced by: endothelium
27
coagulation factor lX
- synonym: christmas factor, plasma thromboplastin component (PTC)
- produced by the liver
- dependent on: vitamin K
28
coagulation factor X
- Stuart-prower factor, Stuart factor
- produced by: liver
- dependent on: vitamin K
29
coagulation factor Xl
- synonym: plasma thromboplastin antecedent (PTA)
- produced by: liver
30
coagulation factor Xlll
- synonym: fibrin-stabilizing factors (FSF) Fibrinase, Laki-Lorand factor
- produced by: liver
30
coagulation factor Xll
- synonym: hageman factor glass activation factor
- produced by: liver
31
3 rules for sampling blood for coagulation test:
- clean puncture (avoids tissue injury)
- correct vial
- procedure (know what you are grabbing, where you are sending it, and how the lab wants it)
32
define hemostasis:
- the stoppage of blood which leads to the maintenance of proper blood flow
33
what is the end result of hemostasis?
- formation of a fibrin clot (mad of platelets and fibrin to prevent hemorrhage)
34
what are the 3 mechanisms hemostasis is dependent on?
- vascular integrity (the response of blood vessels to injury)
- platelet response (number and function)
- coagulation (stimulation of the clotting cascade)
35
describe the mechanisms dependent on vascular integrity for hemostasis
- smooth muscle of the arteries and arterioles contract almost immediately when the vessel is damaged
- sympathetic ns reflex
- the contraction is due to local stimulation of the muscle fibers
- this creates turbulence in which platelets may begin to attach
- most veins and capillaries rely on the contraction of the surrounding tissue
36
describe the mechanisms dependent on platelet response for hemostasis
- with vasculature injury, platelets are attracted to the charged surface of exposed sub-endothelial collagen
- this exposure activates the platelets to alter their surface membrane properties (become sticky and adhere to the vessel wall and to each other with the help of von Willebrand factor, instantly change shape, releases cytoplasmic granules)
- cytoplasmic granules stimulate rapid adherence and maintain vasoconstriction
37
what platelet membrane properties are altered when there is damage to the vasculature?
- become sticky and adhere to the vessel wall and each other with the help of the von Willebrand factor
- instantly changes shape
- releases cytoplasmic granules
38
what are the quantitative platelet responses?
- thrombocytosis
- thrombocytopenia
39
what is a qualitative platelet response?
- something that damages or inhibits platelets
40
what substances are in the platelet's cytoplasmic granules?
- ADP
- serotonin
- histamine
- thromboxane A2
41
describe the mechanisms dependent on coagulation for hemostasis.
- numerous soluble proteins (factors) and other substances are inactive in the bloodstrream
- when activated, they change the physical form of blood in the region of trauma from a liquid to a semi-liquid structure
- chain reaction
- each factor initiates the next factor
42
what are 2 non-protein essential molecules for coagulation?
- vitamin K
- calcium
43
How many pathways exist that can activate the formation of a clot?
2
intrinsic and extrinsic pathway
44
describe the function of vitamin K in clotting.
- promotes clotting by increasing the synthesis of prothrombin
- factors 2,7, 9 and 10 are vitamin k dependent
45
describe the function of calcium in clotting
- necessary as a cofactor to activate many of the clotting factors
46
together, the intrinsic and extrinsic pathways activate what?
the common pathway
47
describe the intrinsic pathways
- occurs in the blood vessel
- leads to the activation of factor X (the point of convergence for the intrinsic and extrinsic pathways)
- activated by factors within the bloodstream (eg cell damage)
- activated without tissue contact
48
What factor does the intrinsic and extrinsic pathways lead to?
factor x
49
describe the extrinsic pathway.
- activated by contact with cells, tissue, and/or fluids outside the vessel (eg, needle puncture)
- leads to activation of factor X
- The primary initiator is factor Vll
- basis for the 'cell-based model' of the coagulation cascade
50
what are the three phases of the cell-based model of coagulation?
- initiation
- amplification
- thrombin activation
51
from the cell-based model describes initiation
- first step (site of injury)
- occurs at the site of vascular injury
- factor Vll becomes activated and in turn activates factor X
52
what factor does the initiation phase of the cell-based coagulation activate?
Vll
53
from the cell-based model describe amplification
- second phase
- factor X has been activated and produces a small amount of thrombin
- thrombin activates more platelets
- activated factor X + cofactors + activated platelets = prothrombinase complex= thrombin burst
54
from the cell-based model, describe thrombin activation
- third phase
- the thrombin burst leads to the conversion of fibrinogen to fibrin (a cross-linked fibrin clot)
55
activation of the common pathway
- activation of the intrinsic and extrinsic pathways starts a cascade leading to the common pathway
56
what is the result of the common pathway?
- the conversion of fibrinogen to fibrin
- fibrin forms a loose mesh which, in the presence of factor Xllla, forms covalent crosslinks that convert fibrin (soluble) to a dense aggregation of fibers (where the fibrin is no longer soluble)
- the mesh traps platelets and RBCs, forming a blood clot
- this process starts in as little as 15 seconds
- can be completed in 5 minutes
57
in the common pathway, describe the breakdown of fibrin
- tPA and plasmin
- break down soluble fibrin into fibrin degradation products
- breaks insoluble fibrin into insoluble FDPs and D-Dimers (protein D-fragments from clot breakdown)
58
describe primary hemostasis
- needs vitamin K and Calcium
- formation of a clot (platelet plug)
- the intrinsic and extrinsic pathways
- mechanical phase
59
describe secondary hemostasis
- activation of the common pathway (factor X)
- Ca+ lll + PF3 = prothrombin activator
- the clot is stabilized by fibrin
- this is the chemical phase
60
describe tertiary hemostasis
- clot is degraded to re-open the vascular lumen
- as each factor is activated to stimulate the next step, it will be rapidly destroyed by local enzymes (eg fibrinolysis [plasmin])
- this helps contain the coagulation to the damaged region
- clot formation is a balance between stimulation of formation and removal
- once the damaged vessel is repaired, the clot will be removed
61
what 3 factors are evaluated for clotting?
- vascular integrity
- platelet integrity
- coagulation
62
reasons for platelet testing
- prolonged bleeding after minor trauma
- prolonged bleeding after partition
- dark, tarry stool (melena)
- evidence of bleeding into cavities
- evidence of hemorrhage (petechiae, ecchymoses, hematoma, epistaxis)
- a potential bleeding disorder
- pre-sx
63
describe the clot retraction test
- a coagulation test
- simple and easy
- tests platelet function
- take a blood sample and in a red top tube allow it to clot (37 degrees Celsius)
- after one hour, there should be some serum squeezed out of the clot
- after 24 hours, the clot should be maximally contracted and should be no lysis
64
what does activated clotting time evaluate?
all clinically significant clotting factors except factor Vll
65
which coagulation test may be affected by thrombocytopenia?
Activated clotting time
66
which is the most sensitive test of the intrinsic and common pathways?
activated partial thromboplastin time
67
what does prothrombin time screen for?
Vitamin K antagonist poisoning
68
which test is used to detect DIC?
fibrin degradation products; fibrin split products
69
where is the fibrinogen protein produced?
the liver
70
what increases the synthesis of fibrinogen?
inflammation
71
what does buccal mucosal bleeding time detect?
- abnormal platelet function
- screens for von Willebrand disease
72
name the 7 coagulation tests
- Russell's viper venom test
- activated clotting time
- fibrin degradation products; fibrin split products
- buccal mucosal bleeding time
- activated partial thromboplastin time
- prothrombin time
- fibrinogen determination; thrombin time
73
what are the 2 categories of hemostatic disorders?
primary and secondary coagulation disorders
74
describe primary coagulation disorders
- are rare and inherited
- is a defect in the production of a coagulation factor (or something assisting a factor)
- affects concentration and function of coagulation factors
- The most common is von Willebrand disease
75
primary coagulation disorders are especially rare in which species?
cats
76
5 known examples of primary coagulation disorders
- factor Vll deficiency (hemophilia A)
- factor lX deficiency (hemophilia B)
- Factor X and Xl
- deficiency of von Willebrand factor (most common)
77
describe von Willebrand's disease
- is a family of related diseases caused by the von Willebrand Factor (vWF)
- vWF is a blood glycoprotein that aids in platelet adherence and carries clotting protein factor Vlll to the site of injury
78
what breed is von Willebrand disease common in?
dobermans
79
what other disease is von Willebrand disease often seen with?
hypothyroidism
80
which species is von Willebrand disease seen in?
- dogs
- rabbits
- swine
81
what are the three categories of secondary hemostatic disorders?
- vascular disorders
- platelet disorders
- coagulation factor disorders
82
describe secondary coagulation disorders
- acquired disorder
- most bleeding disorders in vet med are secondary to some other disease process
83
what diseases can affect secondary coagulation?
- decreased or increased destruction of platelets (thrombocytopenia is most common)
- infectious agents (Parvovirus, Ehrlichia, Dirofilaria)
- nutritional deficiencies
- liver disease (due to decreased production of coagulation factors)
- medications (eg. aspirin can cause bleeding disorders)
- toxic substances (rat poison)
84
describe what can occur if secondary hemostatic vascular disorder occurs
- prolonged bleeding time
- trauma
- septicemia
- viremia
- anaphylaxis
85
what are the 2 categories of platelet disorders
- quantitative abnormalities
- qualitative abnormalities
86
describe qualitative platelet disorders
- certain drug therapies can affect platelet function
- systemic diseases
87
describe quantitative secondary hemostatic platelet disorders
- Platelet destruction/production is affected
- thrombocytosis and thrombocytopenia
- autoimmune disease
- infectious agents (viruses, bacteria, fungi, parasites)
88
describe secondary hemostatic coagulation factor disorders
- liver disease
- nutrient deficiencies (calcium, vitamin K) (often due to the ingestion of Coumarin derivatives)
89
DIC (what does it stand for)
Disseminated intravascular coagulation
90
describe DIC
disseminating intravascular coagulation
- is associated with many pathologic conditions
- a hemostatic disorder where the normal processes of coagulation and fibrinolysis are not performed in equilibrium (clots are formed faster than they are disintegrated)
- is often seen in cases of trauma or infectious disease
- frequently present as systemic hemorrhage or microvascular thrombosis
- will see true schistocytes
- most patients with DIC have alterations in 3 or more coagulation tests, including APTT, elevated fibrinogen and thrombocytopenia
- due to the primary issue
- increased chance of hemorrhage
91
what are the 3 different vacutainers used for the different coagulation tests?
- lavender (EDTA for platelet evaluation)
- sodium citrate (for factors test)
- red top (for activated clotting time test)
92
what coagulation tests need a lavender vacutainer?
platelet evaluation
93
which coagulation tests used sodium citrate vacutainers?
factor tests
94
which coagulation tests use a red top vaccutainer?
clotting time tests
95
what should be done to the sample in order to transport it?
- must be centrifuged
- plasma must be frozen
