Hemostasis

Question 1

What are the non-enzymatic coagulation factors?

Answer 1

Tissue Factor (III)

Factor Va

Factor VIIIa

Calcium and PLTs

Question 2

What binds and activates Prothrombin (II) to make Thrombin (IIa)?

Answer 2

Factor Xa

Question 3

What binds and activates Fibrinogen (I) to make Fibrin (Ia)?

Answer 3

Thrombin (IIa)

Question 4

The part of secondary hemostasis involving activation of Factor X, Prothrombin to Thrombin, and Fibrinogen to Fibrin is know as:

Answer 4

The common pathway

Question 5

What are the 3 phases of Cell Based coagulation model?

Answer 5

Initiation
Amplification
Propagation

Question 6

This is the activator of coagulation in vivo. It is expressed on cells outside the vasculature, and is exposed when the endothelium is disrupted.

Answer 6

Tissue Factor (III)

Question 7

What binds the circulating Factor VIII:vWF complex, causing the release of vWF and activation of VIII to VIIIa?

Answer 7

Thrombin (IIa)

Question 8

What is the primary amplifier in primary and secondary hemostasis?

Answer 8

Thrombin

Question 9

During propagation, large amounts of ______ are produced, and a clot begins to form.

Answer 9

Fibrin

Question 10

Fibrin is originally produced in a soluble form, but becomes cross-linked with the help of ____ to complete the clot.

Answer 10

Factor XIII

Question 11

Tissue Plasminogen Factor (TPA) is continually secreted by endothelial cells. TPA and Plasminogen bind to Fibrin, where TPA cleaves Plasminogen, forming _____.

Answer 11

Plasmin

Question 12

What is the function of Plasmin?

Answer 12

Break down Fibrin strands

Question 13

The breakdown of Fibrinogen and Soluble Fibrin by Plasmin leads to what by-products?

Answer 13

Fibrin Degradation Products (FDPs)

Question 14

The breakdown of cross-linked Fibrin by Plasminogen leads to what by-products?

Answer 14

D-dimers

Question 15

What can measuring D-dimers and FDPs tell us?

Answer 15

How many clots are being formed and broken down.

*DIC!

Question 16

_______ is involved in fibrinolysis, while ______ inhibits coagulation.

Answer 16

Plasmin; Antithrombin

Question 17

How does antithrombin inhibit coagulation?

Answer 17

Inhibits Factor Xa and Thrombin

*Without Thrombin, Fibrinogen can’t be activated to form Fibrin.

Question 18

What protein in circulation binds to antithrombin to express its thrombin binding site and increasing its activity by 1000x?

Answer 18

Heparin

Question 19

After heparin is released from antithrombin, AT is able to bind with thrombin and form the ___ ______, which is removed from circulation by phagocytes.

Answer 19

TAT complex

Question 20

What type of coagulation would you expect in a patient with protein-losing nephropathy?

Answer 20

Hyper coagulation!

*Antithrombin is REALLY small, so it’s one of the first molecules to leak out with glomerular injury.

Question 21

What are the 2 good tests we like to use to measure coagulation activity?

Answer 21

PTT (activated partial thromboplastin time)

PT (prothrombin time)

Question 22

What anticoagulation factors can we measure to determine fibrinolytic activity?

Answer 22

FDPs

D-dimers

Question 23

What anticoagulation factor can we measure to determine inhibitor consumption?

Answer 23

Antithrombin (AT) level

Question 24

What tube is blood collected in for coagulation panels?

Answer 24

Sodium citrate tube (blue top)

Question 25

Sodium citrate tubes are centrifuged to leave plasma and remove RBCs, WBCs, PLTs and Ca++. How do we determine coagulation function from the plasma?

Answer 25

Add back Ca++ and PLTs in controlled volumes

Question 26

You are performing an activated partial thromboplastin time (aPTT) test on a dog. You add contact activator, calcium and PLT substitute to your citrated plasma and determine that the coagulation time is prolonged. What is the minimum deficiency of coagulation factors in this dog and which factors are affected?

Answer 26

There is at least a 70% deficiency in factors in order for the aPTT to be prolonged. Affected factors will be from the intrinsic pathway or the common pathway (XII, XI, IX, VIII ; X, V, II I)

Question 27

The Activated Clotting Time test (ACT) is inexpensive and uses whole blood + contact activator to measure fibrin clot formation. Although it is an easy way to test the intrinsic and common pathways, why isn't it commonly used?

Answer 27

Requires a 95% deficiency in factors to be detected as prolonged.

Question 28

You are performing a prothrombin time (PT) test on a dog. You add tissue factor, Ca++, and PLT substitute to your citrated plasma and determine that the clotting time is prolonged. What deficiencies can this indicate?

Answer 28

Prolonged PT can indicate 70% deficiency in Factor VII (extrinsic pathway) or X, V, II, I (common pathway) It can also be a good test for Vit K deficiency since Factor VII is Vit K dependent.

Question 29

Measurement of FDPs and D-dimers is done by immunologic methods, using _______ to identify fibrin fragments and D-dimer antigens.

Answer 29

Antibodies

Question 30

What can increased FDPs and D-dimers indicate?

Answer 30

Increased fibrinolysis (DIC!) Severe internal hemorrhage with fibrinolysis Decreased clearance of FDP by the liver (live dz)

Question 31

In pathologic conditions, what does a severely increased amount of FDP have on platelets?

Answer 31

Inhibits platelet function (DIC)

Question 32

What are the patterns of hemorrhage in coagulation disorders?

Answer 32

IM hematomas Ecchymosis Bleeding into cavities (thorax/abdomen) Bleeding into joints Blood in stool/vomit/urine

Question 33

A dog is brought into the ER after ingesting a piece of rat bait. He is dyspneic, anemic, weak, and is unable to walk. A blood test confirms that the anemia is regenerative, and PLT counts are normal. You perform a PT, which is prolonged. What is the mechanism of the anemia?

Answer 33

Internal hemorrhage due to warfarin poisining. *Coumarin is a Vit K antagonist, which affects Vit K dependent coagulation factors X, IX, VII, II. PT and PTT will both be prolonged

Question 34

The rat bait dog is decontaminated in clinic and receives a blood transfusion. What is the home treatment plan?

Answer 34

Vitamin K supplements 7 days for Warfarin 3-4 weeks for 2nd generation Warfarin derivatives (Test PT before discontinuing treatment plan)

Question 35

What are the potential causes of DIC?

Answer 35

Induction/exposure of tissue factor Endothelial damage exposing collagen Proteolytic enzymes Stagnant blood flow

Question 36

Snake venoms and trypsin release during pancreatitis cause DIC by what mechanism?

Answer 36

Proteolytic enzymes

Question 37

Necrosis, sepsis, and neoplasia cause DIC by what mechanism?

Answer 37

Exposure of tissue factor

Question 38

An ER patient with sepsis is currently suffering from thrombosis and ischemia to the organs, causing renal and respiratory failure. What phase of DIC is this?

Answer 38

1st phase. Hypercoagulation.

Question 39

The same septic ER patient is now suffering from uncontrolled bleeding, and severely reduced PLTs, coagulation factors, and AT. What phase of DIC is this patient in?

Answer 39

2nd phase. Consumptive phase.

Question 40

Why is there an increase in FDPs with DIC?

Answer 40

Increased thrombus formation leads to increased fibrinolysis, which leads to increased degradation products. *FDP concentration this high also inhibits fibrin polymerization, which makes hemorrhage worse in combination with depletion of coagulation factors!

Question 41

In DIC, mucosal bleeding is due to _____ consumption, while hemorrhage is due to _____ consumption.

Answer 41

platelet; factor

Question 42

A very sick dog presents to your clinic and your tests indicate that she has a moderate thrombocytopenia, prolonged PT/PTT, increased FDPs and D-dimers, and you see schistocytes on the blood film. What secondary disorder are you worried about and how do you proceed with treatment?

Answer 42

DIC Try to identify and eliminate the underlying disorder, start fluid therapy, give blood transfusion.

Question 43

You are about to perform a liver biopsy on a cat with a suspected liver disease. What should you screen for prior to biopsy?

Answer 43

Coagulation disorders Liver disease = decreased synthesis of coagulation factors or production of dysfunctional factors. These animals may bleed excessively.

Question 44

A client brings in a foal with a small cut that hasn't stopped bleeding. PLT counts and PT are normal, but PTT is prolonged. Given the age and history of the patient, you suspect Hemophilia A. Which factor is deficient in this case?

Answer 44

VIII

Question 45

If a young dog has a deficiency in coagulation factor IX, what inherited disorder does he have?

Answer 45

Hemophilia B

Question 46

A cat with a prolonged PTT, normal PT, and no signs of bleeding has a deficiency in what coagulation factor?

Answer 46

XII (Hageman's disease)