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List the parts of the normal hemostatic mechanism.
- primary hemostasis: vessel wall & thrombocytes
- secondary hemostasis: coagulation factors form fibrin
- fibrinolysis: plamin dissolves fibrin
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List 5 different mechanisms by which hemostatic disorders can be produced.
- thrombocytopenia
- thrombocytopathy
- hemophilia A & B
- von Willebrand's disease
- coumarin toxicity
- DIC
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List 6 different clinical signs associated with hemostatic disorders.
- petechiae & ecchymosis
- epistaxis
- hematuria
- melenia
- ocular hemorrhage
- gingival bleeding
- bruises
- hematomas
- bleeding into sub q, muscles, and joints
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Which anticoagulant is used for coagulation factor tests?
sodium citrate
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Define megakaryocyte.
cell in bone marrow that thrombocytes break off of
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Define activated clotting time.
tests intrinsic/common pathways (secondary hemstasis)
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Define petechia
little hemorrhages
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Define epistaxis.
nose bleed
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Define coumarin.
rodenticide
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Define DIC
clots occuring intravascularly all over the body.
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Define melena.
digestive blood in poop
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Name 3 inherited hemostatic disorders.
- Hemophilia
- vonWillebrand's disease
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Name 4 diseases often associated with hemostatic disorders.
- DIC
- vonWillebrand's disease
- hemophilia
- coumarin toxicity
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List three pathophysiologic mechanisms by with a thrombocytopenia may be produced.
- decreased production
- increased destruction
- consumption
- sequestration
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List three different tests which may be run on the SCA 2000.
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What is hemostasis?
- coagulation
- blood clotting
- a protective mechanism
- prevents blood loss due to minor injury
- protects against disorders that cause bleeding
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What is thrombocytopathy?
disease of thrombocytes not functioning correctly
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What is thrombocytopenia?
decrease in the normal amount of thrombocytes
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What does DIC stand for?
dissemenated intravascular coagulation
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What happens when there is injury to the vessel wall?
vasoconstriction occurs within seconds which stimulates the release of factor III
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How long does vasoconstriction last when there is injury to the vessel wall?
lasts less than 1 minute
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Are vasculopathies rare?
yes
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Where are thrombocytes produced?
in bone marrow
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What do thrombocytes adhere to?
subendothelial collagen of vessel walls
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What do thrombocytes release?
bioactive substances
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What do thrombocytes stimulate?
second degree of hemostasis
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Where are clotting factor produced?
in the liver
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Which clotting factor is not produced in the liver?
calcium
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How many clotting factors are there?
12
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What do clotting factors function as?
enzymes activating on another
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Do we need all 12 clotting factors to get fibrin?
yes
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What happens if we do not have all 12 clotting factors?
unstable clot that will cause bleeding again
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What are the three different chemical reactions in clotting factors?
- intrinsic pathway
- extrinsic pathway
- common pathway
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What is the end result of the clotting factors pathway?
fibrin
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What does fibrin do?
stabilizes platelet plug
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What does anticoagulants do? What does EDTA specifically act on? Heparin?
- act on clotting factors to prevent clotting
- EDTA removes calcium from the blood
- Heparin prevents prothrombin from converting to thrombine
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What are the clotting factors in the extrinsic pathway?
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What are the clotting factors in the intrinsic pathway?
factors XII, XI, IX, VIII, VI, Ca
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What are the clotting factors in the common pathway?
Factors X, V, IV, III, II, I
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Which clotting factor is the most important in the extrinsic pathway? What is it specifically?
-
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Where are the intrinsic pathways?
- all within the vessel
- already found in blood
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How is the extrinsic pathway activated?
tissue factor III activated by tissue injury
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What is needed to make factor VII?
vitamin K
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What is the common pathway?
where intrinsic and extrinsic pathways come together
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In the common pathway, X, V, and calcium activate what? What does the reaction do?
- X, V, and calcium activate factor II
- prothrombin turns to thrombin
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Factor II activate what? What does this reaction do?
- factor II activates factor I
- fibrinogen turns to fibrin
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What are the signs and defects of secondary hemostasis?
- bruises and hematomas
- bleeding into sub q, muscles, and joints
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When does fibrinolysis occur?
after the clot has formed
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In fibrinolysis, plasminogen is converted to what?
plasmin
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Plasmin are fragments of what?
fibrin
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Where is fibrin removed?
by the liver
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Is a detailed history from the owner important when diagnosing hemostatic disorders?
yes
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What can hemostatic signs be due to?
anemia
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When do we do screening tests for a hemostatic disorder?
when we suspect a clot disorder
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What kind of controls can we use when doing screening tests for hemostatic disorders?
normal animals in the hospital
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How many platelets are normal in an oil field?
8 - 10
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What will make the platelet count appear low?
clumping
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When should we do a direct thrombocyte count?
within 4 hours of collecting the blood or they will disappear
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Which species thrombocyte count is usually inaccurate when using an automated counter?
cats
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At what platelet count do we usually see signs of hemostatic disorders?
< 50,000
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What are the mechanisms of thrombocytopenia? And what causes each one?
- decreased production: drugs, anaplasma platys, FeLV
- increased destruction: immune mediated, modified live virus, drugs
- consumption/sequestration: DIC, splenic torsion, sepsis
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What is sepsis?
local or generalized invasion of the body by pathogenic microorganisms or their toxins
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How do we check thrombocyte morphology?
check a blood smear
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What do we look for in thrombocyte morphology?
- large platelets
- schistocytes
- organisms
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What causes large platelets?
- megakaryocytic hyperplasia (young platelets)
- a regenerative response
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What are schistocytes?
rbc fragments
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When do we usually see schistocytes?
in DIC or vascular neoplasia
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What is cyclic thrombocytopenia?
thrombocytopenia that comes and goes
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What are the different tests we can do for hemostatic disorders?
- bleeding time
- clot retraction
- activated clotting time
- partial thromboplastin time (PTT)
- prothrombin time (PT)
- blood coagulation analyzers
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What kind of blade do we use for the bleeding time test?
#11
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When is the bleeding test over?
when a clot forms
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How do we do the buccal mucosal bleeding test?
- cut a hairless area (gums work best)
- gentle blotting with no pressure
- note time until clot forms
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What are the normal times for a clot to form in a dog? Cat?
- dog: 1.7 - 4.2 min
- cat: 1.4 - 2.4 min
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What does bleeding time evaluate?
primary hemostasis
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The most common reason we see a bleeding defect is due to _____. Most common type of _____ is _____.
- thrombocytopenia
- thrombocytopenia
- immune mediated
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If there is a prolonged bleeding time then we know we have a problem with what?
vessel wall
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What is clot retraction?
crude test of platelet function
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How do we do a clot retraction test?
- leave blood in a tube without anticoagulant
- clot should retract from the wall of the tube within 1 hour
- we consider it a problem if it takes more than 24 hours - suggests platelet malfunction
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How do we do an activated clotting time test?
- must use a vaccutainer
- avoid the first few drops of blood
- fill a 2ml ACT tube
- warm the tube and blood to body temperature
- leave in the warmer for 50 second, and invert every 10 seconds
- note the time the blood clots
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What is in the ACT tube?
diatomaceous earth...dinosaurs :(
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How long should it take a dogs blood to clot during the activated clotting time test? Cats?
- dog: 60 - 110 seconds
- cat: 50 - 75 seconds
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If an animal has thrombocytopenia what will happen during the activated clotting time test?
will automatically be prolonged giving us false results
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What does partial thromboplastin time test?
intrinsic/common pathways
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Which test is more sensitive, PTT or ACT?
PTT
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What does PTT stand for?
partial thromboplastin time
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What time of plasma must we use for the PTT test and what tube do we use to get it?
- citrated plasma
- blue top tube (sodium citrate)
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What is PTT used to diagnose?
hemophilia
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Do we need to fill the sodium citrate tube completely when running the PTT test? Why or why not?
- yes
- must have the appropriate ratio of blood to sodium citrate
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When should we run the PTT test?
within 3-4 hours of collecting the blood
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What does the prothrombin time test for?
- extrinsic/common pathways
- tests for factor VII
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What does PT stand for?
prothrombin test
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What kind of plasma is needed to run PT test?
citrated plasma
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When should we run the PT test?
within 2 hours of collecting blood
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What does PT mostly diagnose?
coumarin toxicity and DIC
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What are the most common blood coagulation analyzers?
- COAG Dx (formally SCA 2000)
- VS Pro (Abaxis)
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What kind of test does the COAG DX (SCA 2000) run?
-
What does the COAG Dx (SCA 2000) evaulate?
evaluates intrinsic, extrinsic, and common pathways
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What kind of tests does the VS Pro (Abaxis) run?
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What is von Willebrand's disease?
- an inherited bleeding disorder
- deficiency of vW factor
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What is the vW factor?
chemical that facilitates platelets attaching
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What does the vW factor carry?
factor VIII
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von Willebrand's disease has a deficiency of what?
vW factor
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How do we test for vWf (vW factor)?
- send out citrated plasma
- separate immediately, freeze quickly
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Are there genetic tests available for von Willebrand's disease?
yes
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What is DIC?
massive stimulation of clotting mechanisms
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What are some clinical signs of DIC?
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What is usually the outcome of DIC?
death usually occurs
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What are some common causes of DIC?
- pancreatitis
- heartworm disease
- RMSF
- ICH
- FIP
- feline panleukopenia
- GDV
- neoplasia
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How do we diagnose DIC?
- initiating condition present
- bleeding/organ failure (petechiae/ecchymoses)
- TCP
- all coagulation tests are prolonged
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What is hemophilia?
unable to clot blood
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What are the two types of hemophilia?
-
Is hemophilia inherited?
yes, sex linked
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Which chromosome is hemophilia carried on?
X
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What type of deficiency does hemophilia A have?
factor VIII
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What type of deficiency does hemophilia B have?
factor IX
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What test is prolonged when we have a patient with hemophilia?
PTT
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What is coumarin toxicity?
rodenticides
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What does coumarin block?
vitamin K
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What factor does coumarin toxicity lack?
factor VII
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How is coumarin toxicity diagnosed?
- history
- prothrombin time is prolonged
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Which tests are normal with coumarin toxicity?
-
What is in rodenticides that causes the calicum in an animal to increase?
cholecalciferol
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What are vascular disorders?
disease of vessels
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What type of diseases are vascular disorders?
- vasculities (FIP)
- hyperadrenocortisim (cushings)
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How are vascular disorders diagnosed?
- history
- signs
- eliminating other possibilities
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