Haemostasis Flashcards
Primary hemostasis has 3 main components. What are they?
- Endothelium injury exposing collagen and releasing vWF
- vWF adheres platelets to endothelium
- Platelets - adhere, change shape, secrete, aggregate
What are the Vi-K dependent enzymes related to coagulation?
II, VII, IX, X
What factors are from the extrinsic pathway that feed into tenase?
VIIa-TF-Ca2+
What factors from the intrinsic pathway feed into tenase?
VIIIa-IXa-Ca2+ - PF3
What factors go into prothrombinase?
Va-Xa-Ca-PF-3
What causes coagulation inhibition?
Antithrombin III inhibits intrinsic & common pathways
TF inhibitor is an extrinsic pathway inhibitor, inhibits LACI, extrinsic tenase
What is fibrinolysis?
Blood clot lysis mediated by serine protease plasmin
Plasminogen is activated by…
tPA (tissue plasminogen activator)
UPA (urokinase PA)
tPA & UPA activators are inhibited by…
PAI-1 (plasminogen activator inhibitor 1) which binds free tPA
plasmin is inhibited by:
alpha2-antiplasmin
alpha2-macroglobulin
Plasmin formation is inhibited by
TAFI (thrombin-activatable fibrinolysis-inhibitor)
What does TAFI do?
Plays important role in stabilizing the fibrin clot, protecting it from lysis
TAFI is activated by
thrombin, especially with thrombomodulin as a cofactor
TAFI inactivates…
bradykinin which causes vasodilation, non-vascular smooth muscle contraction, increased vascular permeability, pain
What causes hemorrhagic diatheses?
- Deficiency/defective coagulation factors
- Quantitative or qualitative defects of platelets
- Diffuse endothelial injury
- Bleeding including hematoma, sites of mechanical stress, hemarthroses, purpura
Prothrombin time tests
the extrinsic and common coagulation pathways
Activated partial thromboplastin time tests
the intrinsic and common coagulation system
What tube is required for coagulation tests?
Na citrate blood
Thrombin time measures
the time it takes to convert fibrinogen to fibrin
Activated clotting time tests
the intrinsic system
FDP’s increase as…
fibrinogen is cleaved by plasmin
D-dimer increases as
X-linked fibrin is cleaved by plasmin
ATIII decreases as
it is consumed by binding clotting factors
PT increases when
APTT increases
When would you suspect Bleeding diathesis?
- prolonged bleeding after a minor cut/wound
- bleeding defect in newborns
- access to poisons
- purpura - small bleeding sites in skin & MM’s
- Petechiation - pinpoint bleeding MM’s, platelets decreased
- bleeding into body cavity or into muscle/eye
- Txt w/ aspirin, estrogen, bute, heparin
What are some hereditary bleeding disorders?
Haemophilia A-D
What results would you expect if a patient had haemophilia A & B?
prolonged APTT, normal PT
Hemophilia A is sex-linked in what species?
dog, cat, horse
An increase in APTT may demonstrate…
Classic hemophilia A (VIII)
Hemophilia A affects…
VIII (Antihemophilic factor A)
Hemophilia B affects…
IX (Christmas factor)
Hemophilia C affects…
XI (plasma thromboplastin antecedent - PTA)
Hemophilia D affects
XII (Hageman factor)
What are some inherited coagulation defects?
I: Congenital afribrinogenemia
II
VII
VWF deficiency
What are some acquired disorders?
Vit K Def/antagonism
DIC - consumption coagulopathy
Angiostrongylus vasorum
What are some clinical signs of vit K deficiency/antagonism?
Anemia
Weakness
Pallor
Epistaxis
Weakness
What abnormalities might be see on coagulation tests when DIC is in progress?
APTT, PT increases
FDP/D-Dimer +
ATIII decreases
Antiaggregant of platelets produces
nitric oxide aka EDRF (endothelium-derived relaxation factor)
What are common anticoagulants?
Heparin
Thrombomodulin
TPA
DDAVP is used to treat
vWF deficiency
