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Hemostasis
Dr. Porter test 1
63
Veterinary Medicine
Undergraduate 2
08/29/2013

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Term
What is hemostasis?
Definition
The process of forming blood clots. A protective mechanism.
Term
What are the two hemostatic mechanisms?
Definition
-Primary hemostasis
-Secondary hemostsis
Term
What does primary hemostasis deal with?
Definition
the vessel wall and thrombocytes
Term
What does secondary hemostasis deal with?
Definition
Coagulation factors that form fibrin
Term
Injury of the vessel wall results in what?
Definition
Vasoconstriction
Term
What does vasoconstriction do?
Definition
-Cuts down on blood flow temporarily
-Stimulates release of factor III
Term
Where are thrombocytes produced?
Definition
The bone marrow
Term
When a cut is made in the skin, what do the thrombocytes do?
Definition
-adhere to subendothelial collagen of vessel wall
-release bioactive substance (which stimulates extrinsic and intrinsic pathways
-Aggregate forming plug
-Stimulate secondary hemostasis
Term
What is a megakaryocyte?
Definition
the "mother of thrombocytes"
bits of broken off pieces form platelets
Term
What is petechiae?
Definition
small purple dots on the skin (small bruising)
Term
What is ecchymoses?
Definition
wide spread purple marks on the skin (larger bruising)
Term
What is epistaxis?
Definition
bleeding fromt he nose
Term
Are clotting factors categorized under primary or secondary hemostasis?
Definition
Secondary
Term
Where are the clotting factors produced?
Definition
Most are produced in the liver
Term
Are all clotting factors proteins?
Definition
No, Calcium is not. The rest are.
Term
How do the clotting factors function as enzymes?
Definition
They activate eachother causing a chemical reaction
Term
What is the end point of the intrinsic and extrinsic pathways?
Definition
Fibrin
Term
What does fibrin do?
Definition
stabilizes the platelet plug
Term
If any clotting factors are missing or defective, what happens?
Definition
It inhibits the making of fibrin
Term
What is different about factor III compared to the other clotting factors?
Definition
It comes from the vessel wall, not the liver
Term
What is the goal of the intrinsic pathway?
Definition
To activate factor X
Term
Is factor VII part of the intrinsic or extrinsic pathway?
Definition
Extrinsic
Term
What is the common pathway?
Definition
Where the intrinsic and extrinsic pathways come together
Term
How does heparin work to prevent clotting?
Definition
It blocks the making of thrombin from prothrombin
Term
How does EDTA work to prevent clotting?
Definition
It pulls the calcium out of the blood. This process is called chelating
Term
What are some signs of secondary hemostasis?
Definition
-Bruises and hematomas
-Bleeding into the SQ, muscles, and joints
Term
When does fibrinolysis occur?
Definition
After a clot has formed
Term
What is the process of fibrinolysis?
Definition
Plasminogen is converted to plasmin, which breaks down the clot allowing blood to flow again.
Term
Why is it important to get a detailed history on suspected hemostatic patients?
Definition
You need to know how long it has been going on because some disorders are inherited, and some can be caused by drugs or disease
Term
How soon should you do a thrombocyte count after collecting the sample?
Definition
Within 4 hours
Term
If you have a "true" thrombocytopenia, will it be easy to find platelets on a smear?
Definition
No, you will see very few if any
Term
Why should you always do a manual platelet count on cat blood?
Definition
Cat platelet counts on machines are often inaccurate due to similar size of platelets and RBC's
Term
When will you see abnormal results in a thrombocyte count?
Definition
When numbers are less than 50,000
Term
What is the clot retraction test?
Definition
A crude test of platelet function
Term
How is a clot retraction test performed?
Definition
Leave blood in a tube with no anticoagulant. Check tube every 30 minutes for clotting. Clot should retract from walls of tube by 50% within an hour
Term
When is the clotting time considered prolonged?
Definition
If it takes longer than 24 hours for clot to retract
Term
What is the Activated Clotting Time testing for?
Definition
It is a crude test for hemostasis, testing the intrinsic and common pathways.
Term
What does an ACT tube contain?
Definition
Diatomaceous earth
Term
What are the normal ACT's for dogs and cats?
Definition
Dogs: 60-110 sec.
Cats: 50-75 sec.
Term
What will cause these times to be prolonged?
Definition
A factor defect or severe thrombocytopenia
Term
What does the partial thromboplastin time (PTT) detect?
Definition
Intrinsic and common pathways (secondary hemostasis)
Term
What is it used to diagnose?
Definition
hemophilia
Term
What type of plasma must be used?
Definition
Citrated
Term
What tube contains sodium citrate?
Definition
Blue top
Term
Why must you fill the sodium citrate tube completely?
Definition
You must have the correct ratio of citrate and blood (1:9) to get an accurate result
Term
What does the prothrombin time (PT) detect?
Definition
Extrinsic and common pathways (secondary hemostasis)
Term
When would this test have prolonged results?
Definition
With coumarin toxicity
(also in DIC)
Term
What is the most common inherited bleeding disorder?
Definition
Von Willebrand's disease
Term
What is vW disease?
Definition
A deficiency in the vW factor
Term
What does the vW factor do in the coagulation process?
Definition
-facilitates platelets to adhere to eachother
-carries factor VIII
Term
Do signs appear as a primary or secondary disorder?
Definition
Primary, unless it is severe, then it would show secondary signs
Term
What type of plasma is used in testing for the vWf?
Definition
Citrated
Term
Which breed is most likely to have von Willebrand's disease?
Definition
Doberman Pinscher
Term
What does DIC stand for?
Definition
Disseminated Intravascular Coagulation
Term
What is DIC?
Definition
Massive stimulation of clotting mechanisms. Clotting everywhere!
Term
What is the hail mary drug given to DIC patients?
Definition
Heparin
Term
What are some common causes of DIC?
Definition
-Pancreatitis
-Heartworm Disease
-RMSF and ICH
-FIP and FeLV
-GDV
-Neoplasia
Term
How can you diagnose DIC?
Definition
-Bleeding/organ failure
-Thrombocytopenia
-All coagulation tests will be prolonged
Term
What is hemophilia A?
Definition
a factor VIII deficiency
Term
What is hemophilia B?
Definition
a Factor IX deficiency
Term
How do you detect hemophilia?
Definition
There will be a prolonged PTT/factor assays
Term
What happens in a coumarin/warfarin toxicity?
Definition
It blocks vitamin K and there is a deficiency in factor VII
Term
How is it diagnosed?
Definition
Often from a patient history as well as prolonged PT
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