Evaluation of Coagulation and Hemostasis Flashcards
What is hemostasis
Maintaining blood in its fluid state while stopping bleeding in case of trauma
What is hemostasis
Maintaining blood in its fluid state while stopping bleeding in case of trauma
What is primary hemostasis
A platelet plug
What is secondary hemostasis
Fibrin clot
What is Tertiary hemostasis
Breakdown of clot
What is the vascular response to injury
There is contraction and narrowing of the lumen of the vessel, which decreases the rate of blood loss and creates a turbulence in which platelets may begin to attach
Loss of endothelium exposes basement membrane (collagen) + releases vWF
Healthy endothelium inhibits platelet activation
Describe primary hemostasis
Formation of the temporary platelet plug
Normally Platelets are exposed only to the linings of the blood vessels (endothelium) and heart (endocardium)
blood vessel injury, platelets are exposed to the subendothelial basement membrane ( collagen)
Damaged endothelium secretes vWF
Describe platelet activation
exposure activates the platelets to alter surface membrane properties (become “sticky”) and to adhere to the vessel wall and each other
What products are released when platelets activate
ADP (adenosine diphosphate )
Serotonin and histamine vasoconstriction
PF 3coagulation cascade
What is purpura
superficial bleeding of skin or mucous membranes
What is petechiae
What is ecchymoses
larger, small arteriole/venule bleeding
What is superficial bleeding
bleeding from mucous membranes (eg epistaxis, hematuria, melena, etc)
What is Von Willebrand factor
vWF helps to make the platelets stick to each other and to form the platelet plug,
It is a protein produced by endothelial cells
What does the Von Willebrand factor cause
Platelet adhesion to collagen
Platelet–platelet binding or aggregation
vWF helps to activate factor VIII
What is Von Willebrand’s disease
most common hemostatic defect in dogs,
Von Willebrand’s factor, is not a clotting factor defect but a protein necessary for the platelets to adhere to the endothelium,
Its absence markedly slows or prevents the formation of a clot - vWF is also cofactor for factor VIII ( hemophilia factor)
What is Von Willebrand
It is a protein complex made up of 3 separate proteins
What is type 1 vWF problem
Type 1- has low amounts of vWF
Doberman Pinscher, the Shetland Sheepdog, the German Shepherd Dog, and the Standard Poodle
What is type 2 vWF problem
Type 2- is missing one of the 3 proteins
German Short-Haired and German Wire-Haired Pointers
What is type 3 vWF problem
Type 3- completely missing vWF factor
Most severe form
How do you treat vWF
Blood product called cryoprecipitate
Can give FRESH Frozen Plasma
hormone called DDAVP (or desmopressin acetate)
What does the DDAVP hormone do when given
It causes sudden release of von Willebrand’s factor into the bloodstream. After a 30-minute onset period, the use of DDAVP shortens the bleeding time for approximately 2 hours after the injection.
Thrombocytopenia
a decrease in platelet number
Thrombocytopathia
a decrease in platelet function
How do you count platelets
Impedance analysers
Clumped platelets may be read as WBC
Cat platelets are very large and clump easily
ALWAYS DO A SMEAR EVALUATION
Should have 10-20 per 40x Field other wise look for clumped platelets
What is the blood mucosal bleeding time
Blood that wells up from the incision is blotted with filter paper applied near (but not touching!!) the incision.
A stopwatch is started when the incision is made and stopped when a crescent of blood no longer develops on the filter paper.
Normal BMBT dogs is
What does a BMBT test show
platelets (number and function), vessel wall defects (rare) and vWf.
What does a prolonged BMBT show
inherited diseases, including vWD
thrombopathia (uremia and aspirin therapy).
thrombocytopenia (probably
In what 2 settings are BMBT used
1- As an in vivo pre surgical screening test for vWD, especially in Dobermans,
Pre Treatment for vWF:
vWF supplementation with fresh or fresh frozen plasma or cryoprecipitate. ( 4 hours)
Injection of Desmopressin –DDAVP ( lasts for 2 hours)
2- As a screening test to identify defects in platelet function (thrombopathia) that cannot be detected with routine hemostatic assays.
What is the capillary bleeding time
Done on lateral shaved ,shaved surface of front toe with sphygmomanometer cuff on at a pressure of 60 mm hg
The skin is cut twice with a lancet
Bleeding should stop in 1 – 2.5 minutes
What is the intrinsic pathway
intrinsic pathway consists of factors present within the blood stream that can be activated without tissue contact
What is the extrinsic pathway
extrinsic pathway is activated by contact with cells and tissue fluid outside the vessel. Tissue thromboplastin
What is the common pathway
common pathway – results in formation of the fibrin clot
What does the extrinsic pathway provide
EXTRINSIC PATHWAY factor VII + tissue damage
What does the extrinsic pathway provide
EXTRINSIC PATHWAY factor VII + tissue damage
What is primary hemostasis
A platelet plug
What is secondary hemostasis
Fibrin clot
What is Tertiary hemostasis
Breakdown of clot
What is the vascular response to injury
There is contraction and narrowing of the lumen of the vessel, which decreases the rate of blood loss and creates a turbulence in which platelets may begin to attach
Loss of endothelium exposes basement membrane (collagen) + releases vWF
Healthy endothelium inhibits platelet activation
Describe primary hemostasis
Formation of the temporary platelet plug
Normally Platelets are exposed only to the linings of the blood vessels (endothelium) and heart (endocardium)
blood vessel injury, platelets are exposed to the subendothelial basement membrane ( collagen)
Damaged endothelium secretes vWF
Describe platelet activation
exposure activates the platelets to alter surface membrane properties (become “sticky”) and to adhere to the vessel wall and each other
What products are released when platelets activate
ADP (adenosine diphosphate )
Serotonin and histamine vasoconstriction
PF 3coagulation cascade
What is purpura
superficial bleeding of skin or mucous membranes
What is petechiae
What is ecchymoses
larger, small arteriole/venule bleeding
What is superficial bleeding
bleeding from mucous membranes (eg epistaxis, hematuria, melena, etc)
What is Von Willebrand factor
vWF helps to make the platelets stick to each other and to form the platelet plug,
It is a protein produced by endothelial cells
What does the Von Willebrand factor cause
Platelet adhesion to collagen
Platelet–platelet binding or aggregation
vWF helps to activate factor VIII
What is Von Willebrand’s disease
most common hemostatic defect in dogs,
Von Willebrand’s factor, is not a clotting factor defect but a protein necessary for the platelets to adhere to the endothelium,
Its absence markedly slows or prevents the formation of a clot - vWF is also cofactor for factor VIII ( hemophilia factor)
What is Von Willebrand
It is a protein complex made up of 3 separate proteins
What is type 1 vWF problem
Type 1- has low amounts of vWF
Doberman Pinscher, the Shetland Sheepdog, the German Shepherd Dog, and the Standard Poodle
What is type 2 vWF problem
Type 2- is missing one of the 3 proteins
German Short-Haired and German Wire-Haired Pointers
What is type 3 vWF problem
Type 3- completely missing vWF factor
Most severe form
How do you treat vWF
Blood product called cryoprecipitate
Can give FRESH Frozen Plasma
hormone called DDAVP (or desmopressin acetate)
What does the DDAVP hormone do when given
It causes sudden release of von Willebrand’s factor into the bloodstream. After a 30-minute onset period, the use of DDAVP shortens the bleeding time for approximately 2 hours after the injection.
Thrombocytopenia
a decrease in platelet number
Thrombocytopathia
a decrease in platelet function
How do you count platelets
Impedance analysers
Clumped platelets may be read as WBC
Cat platelets are very large and clump easily
ALWAYS DO A SMEAR EVALUATION
Should have 10-20 per 40x Field other wise look for clumped platelets
What is the blood mucosal bleeding time
Blood that wells up from the incision is blotted with filter paper applied near (but not touching!!) the incision.
A stopwatch is started when the incision is made and stopped when a crescent of blood no longer develops on the filter paper.
Normal BMBT dogs is
What does a BMBT test show
platelets (number and function), vessel wall defects (rare) and vWf.
What does a prolonged BMBT show
inherited diseases, including vWD
thrombopathia (uremia and aspirin therapy).
thrombocytopenia (probably
In what 2 settings are BMBT used
1- As an in vivo pre surgical screening test for vWD, especially in Dobermans,
Pre Treatment for vWF:
vWF supplementation with fresh or fresh frozen plasma or cryoprecipitate. ( 4 hours)
Injection of Desmopressin –DDAVP ( lasts for 2 hours)
2- As a screening test to identify defects in platelet function (thrombopathia) that cannot be detected with routine hemostatic assays.
What is the capillary bleeding time
Done on lateral shaved ,shaved surface of front toe with sphygmomanometer cuff on at a pressure of 60 mm hg
The skin is cut twice with a lancet
Bleeding should stop in 1 – 2.5 minutes
What is the intrinsic pathway
intrinsic pathway consists of factors present within the blood stream that can be activated without tissue contact
What is the extrinsic pathway
extrinsic pathway is activated by contact with cells and tissue fluid outside the vessel. Tissue thromboplastin
What is the common pathway
common pathway – results in formation of the fibrin clot
What does the intrinsic pathway provide
the intrinsic pathway; factors XII, XI, IX, and VIII are components of the intrinsic system.
- mnemonic -it is not $12, but $11.98” (for factors XII, XI, IX, and VIII).
What does the extrinsic pathway provide
EXTRINSIC PATHWAY factor VII + tissue damage
What are the Vitamin K dependant clotting factors
FII, FVII, FIX, FX
Clotting proteins produced by the liver
Require Vit K to be activated
What is deep bleeding
formation of large hematomas or bleeding into body cavities
Large Hematomas
Hemothorax
hemoperotoneum
What happens with a mixed hemostatic defect
Dogs and cats with mixed hemostatic defects (primary plus secondary) develop a combination of petechiae, ecchymoses, mucosal bleeding, hematomas, and intracavitary bleeding. Mixed hemostatic defects are almost exclusively associated with DIC, and are common in dogs and cats
What is DIC
disseminated intravascular coagulopathy
Sometimes called a consumptive coagulopathy
When does DIC occur
DIC does not occur by itself but as a complicating factor from another underlying condition or critical illness.
What are the clinical signs of DIC
Prolonged PT
Prolonged APTT
Increased FDP or D-dimers
Decreased platelets
How do you sample for coagulation tests
Clean venipuncture is essential. Poor venipuncture will result in activation of coagulation due to contamination with tissue factor
if the vein is not entered on the first attempt, a fresh needle should be used.
vacutainer collection is preferred
Blue citrate tube
Plastic tube, not glass
What is the ACT test used for
evaluation of the intrinsic and common pathways
Clotting Factors must be decreased by 95%
Whole blood without anticoagulant is added to a special tube containing diatomaceous earth
tube should be incubated at 37 C
ACT relies on the patient’s platelets for provision of phospholipid to support the reaction – but is not overly prolonged with thrombocytopathias
How do you do a ACT test
evaluation of the intrinsic and common pathways
Clotting Factors must be decreased by 95%
Whole blood without anticoagulant is added to a special tube containing diatomaceous earth
tube should be incubated at 37 C
ACT relies on the patient’s platelets for provision of phospholipid to support the reaction – but is not overly prolonged with thrombocytopathias
What % does a carrier of hemophilia have
A carrier may only have a 40 – 60 % decrease in factor VIII or IX
Bleeding problems occur when you have less than 5% of the factor
What is hemophilia A
Factor VIII deficiency
What is hemophilia B
Christmas disease; Factor X hemophilia
How do you get hemophilia
Sex linked
No breed predisposition
Quite rare
What is the normal ACT in dogs
Normal ACT for dogs is 60 - 90 seconds
Due to reliance on endogenous platelets for the reaction, platelet counts of
What is the normal ACT in cats
For cats is 45 - 160 seconds.
What causes a prolonged ACT
liver disease,
congenital coagulopathies ( hemophilia A and B),
vitamin K-responsive coagulopathies (FII, FVII, FIX, FX)
DIC,
What is the aPTT associated with
intrinsic and common pathways like ACT
Collect in blue top tube ( citrate)
Add a contact surface activator of the intrinsic system + Calcium
It will not be affected by low platelets
What is PT associated with
Extrinsic( VII) and common pathway factors.
Tissue thromboplastin (a source of tissue factor) and calcium are added to the patient plasma and the time for clot formation is recorded. N= 7-10 sec
sensitive indicator of poisoning with anticoagulant rodenticides ( warfarin)
factor VII is the vitamin K-dependent factor with the shortest half-life (approximately 6 hours in the dog), the PT may be prolonged within 24 hours following rodenticide ingestion
What is PIVKA
Proteins induced by Vitamin K Absence
Describe PIVKA
vitamin K-dependent coagulation factors (FII, FVII, FIX, FX) are produced in the liver as nonfunctional precursors
precursors are activated, in the presence of vitamin K,
absence of vitamin K, there is an increase in these precursors
Can detect rodenticide poisoning earlier than 6 hours
What are the Misc tests for coagulation
Clot retraction
Whole blood clotting time
What is fibrinogen
Fibrinogen is an acute phase reactant protein and elevated values are seen in inflammation and renal disease
How do you calculate fibrinogen
Heat precipitation:
2 edta microhematocrit tube
second tube is heated at 56 C for 3 minutes to casuse the firinogen to become fibrin
Spin and measure the protein
The difference between the 2 is the fibrinogen
What is Fibrolysis
Plasminogen, a proenzyme, is activated by F XIIa to Plasmin
Plasmin biodegrades fibrinogen and fibrin, generating fibrin degradation products (FDPs)
FDPs also exert a profound inhibitory effect on platelet function
contributing to the petechiae and ecchymoses in patients with disseminated intravascular coagulation (DIC)
how do you test for tertiary hemostasis
check for Fibrinogen degradation products-FDP
Describe DIC
Prolonged PT
Prolonged APTT
Increased FDP or D-dimers
Decreased platelets
