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74 Cards in this Set
- Front
- Back
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The interaction of what three elements determine whether a patient bleeds, stops bleeding, or develops blood clots?
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- Vessel endothelium
- Platelets - Clotting factors |
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What is the end product of the clotting cascade?
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Fibrin
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What causes vasoconstriction during an injury?
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Endothelin release from endothelial cells
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What starts the clotting cascade?
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Exposure of tissue factor
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Where does the tissue factor lie?
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Underneath endothelial cells
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What increases platelet adhesion to subendothelial collagen?
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von Willebrand Factor
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3 things that occurs in platelets during injury
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- Release stored products from their granules
- Conformation change to expose fibrinogen binding sites - Exposure of platelet phospholipids |
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What are a platelet's phospholipids used for?
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Activation of clotting cascade
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What are platelet's fibrinogen binding sites used for?
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Allows platelets to bind together
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What is formed as a result of exposure of tissue factor?
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Thrombin
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What is thrombin used for?
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Activates fibrinogen to fibrin
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What function does fibrin ultimately have?
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Holds clots together
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What is resolution of the clot (fibrinolysis) mediated by?
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Plasmin
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4 anticoagulants released by blood vessels
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- Prostacyclin
- Nitric oxide - Thrombomodulin - Heparan sulfate |
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What does prostacyclin do? (2)
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- Vasodilation
- Platelet inhibition |
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What does nitric oxide do?
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Vasodilation
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What does thrombomodulin do?
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Inhibits factor Va and VIIIa
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What does heparan sulfate do?
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Inhibits thrombin formation
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4 procoagulant properties
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- von Willebrand Factor
- Plasminogen activator inhibitor type 1 (PAI - 1) - Exposure of sub-endothelial collagen and tissue factor - Endothelin release |
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Lifespan of platelets
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7 - 10 days
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Where is the majority of von Willebrand Factor kept?
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Inside endothelial cells
- Rest is circulating |
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How does thromboxane released from platelets aid in clotting? (2)
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- Vasoconstriction
- Platelet aggregation |
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How does Calcium released from platelets aid in clotting? (2)
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- Essential for clotting cascade
- Necessary for contraction of platelets |
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What are two factors released from a platelet that activate other platelets?
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- Platelet Activating Factor (PAF)
- ADP |
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What does the 'a' after a clotting factor indicate?
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Activated form of the factor
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What is the name of Factor I?
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Fibrinogen
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What is the name of Factor Ia?
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Fibrin
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What is the name of Factor II?
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Prothrombin
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What is the name of Factor IIa?
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Thrombin
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What is the name of Factor III?
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Tissue Factor
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What is the name of Factor IV?
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Calcium
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What is the name of Factor XIII?
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Fibrin stabilizing factor
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What does Vitamin K do in regards to the clotting cascade?
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Used in synthesis of certain factors
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Which four factors is Vitamin K necessary in the formation of?
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- II
- VII - IX - X |
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Which two proteins is Vitamin K necessary for the formation of?
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- C
- S These are inhibitory to clotting |
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Where are factors produced?
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Liver
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Which activated factor circulates in the blood?
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VIIa
- Only 1% of all VII circulates as VIIa though |
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Which four factors are consumed during clotting, and why is this significant?
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- I
- IV - V - VIII They can become depleted |
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How does bleeding differ between coagulopathies and platelet disorders?
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Coagulopathies have more localized and dramatic bleeding
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Two types of coagulopathies
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- Inherited
- Acquired |
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Which coagulopathy type is rare?
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Inherited
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Why do you not see Calcium deficits in coagulopathies?
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Death occurs first
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What's the most common factor deficiency in cats?
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XII
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What's the most common factor deficiency in cattle?
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XI
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Which 4 factor deficiencies lead to spontaneous bleeding?
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- V
- VIII - IX - X |
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Which two factor deficits cause severe spontaneous bleeding?
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- I
- II |
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3 causes of acquired coagulopathies
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- Disseminated intravascular coagulation (DIC)
- Vitamin K antagonism or deficiency - Hepatic disease |
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What four factors and two proteins require Vitamin K for production of normal functional factors?
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- II
- VII - IX - X - Protein C - Protein S |
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What's the most common cause of Vitamin K antagonism?
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Rodenticide toxicity
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What shrubbery leads to Vitamin K antagonism?
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Sweet clover (Mellitus spp.)
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Two test values that will be prolonged due to Vitamin K antagonism/deficiency
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- Prothrombin time (PT)
- APTT |
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Why is Prothrombin time the first test value to change?
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Due to short HL of Factor VII
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Two reasons that animals develop coagulopathies from hepatic disease
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- Failure to synthesize clotting factors and natural inhibitors of the clotting pathways
- Failure to clear fibrin degradation products which interferes with platelet to platelet binding |
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How much of the liver must be affected for a coagulopathy to manifest?
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2/3
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4 tests used to evaluate clotting pathways and factors
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- Activated Clotting Time (ACT)
- Activated Partial Thromboplastin Time (APTT) - Prothrombin Time (PT) - Functional factor assays |
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What does the Activated Clotting Time test use for a sample?
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Whole blood
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How much of a decrease in factors must there be for the Activated Clotting Time test to detect them?
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95% decrease from normal
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What does a prolongation of Activated Clotting Time indicate?
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Decrease in one or more factors in:
- Intrinsic pathway - Common pathway |
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What platelet level is required for Activated Clotting Time test to work?
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> 10,000 platelets/ul
So don't do the test in a patient with less than that because you may get a false positive |
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What pathways does the Activated Partial Thromboplastin Time test?
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- Intrinsic
- Common |
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What does the Activated Partial Thromboplastin Time test require for activation?
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- Ca++
- Phospholipid |
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What must factor levels be to be detected by Activated Partial Thromboplastin Time test?
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30% of normal (70% decrease from normal)
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What pathways does the Prothrombin Test test?
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- Extrinsic pathway (Factor VII)
- Common pathway |
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Coagulation tests that measure the intrinsic pathway
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- ACT
- APTT |
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Coagulation tests that measure the common pathway
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- PT
- ACT - APTT |
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Coagulation tests that measure the extrinsic pathway
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PT
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3 clinical signs of DIC
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- Petechia
- Ecchymoses - Hemorrhage |
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4 coagulation profile tests used to diagnose DIC
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- PT
- APTT - AT - D-dimer |
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3 CBC profile tests used to diagnose DIC
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- Platelets
- Fibrinogen - Schistocytes |
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Which coagulation profile value in DIC is often prolonged first, and why?
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APTT
- Due to consumption of V and VIII because they're not enzymes |
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What's a very sensitive CBC indicator of DIC that's present in the majority of cases?
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Thrombocytopenia
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What's a very sensitive coagulation panel indicator of DIC that's present in the majority of cases?
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D-dimer
- Not pathognomonic, but close. |
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Two plasma components that decrease in DIC
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- Antithrombin
- Fibrinogen |
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What RBC morphology can indicate DIC, and why?
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Schistocytes
- Shearing of RBCs due to increased thrombosis deposition |
