Coagulation / Coagulopathies

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Coagulation / Coagulopathies
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Hemostasis

• Hemostasis is the ability of the bodys systems
  to maintain the integrity of the blood and blood
  vessels.
• Hemostasis involves the arrest of the escape of
  blood by either natural (clot formation or vessel
  spasm), or by artificial (compression or
  ligation) means, or the interruption of blood
  flow to a part, or the artificial stimulation of
  clotting (i.e. electrocautery)

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Hemostasis contd

• Coagulation the formation of a clot.
• Platelets aka thrombocytes. Small, anucleated,
  discoid-shaped, light blue staining cells that
  may have multiple, fine, ping to purple granules
  in the cytoplasm.
• Platelets are formed in the bone marrow. 1/3 of
  the total blood platelets are in the spleen, 2/3
  remain in the circulating blood.
• Due to their adhesion and aggregation
  capabilities, platelets can occlude small breaks
  in blood vessels and prevent the escape of blood.

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Platelets on a Blood Film
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Hemostasis contd

• Hemostasis involves a number of complex pathways,
  platelets, and coagulation (clotting) factors.
• The ability for blood to clot, depends on
  vascular integrity, adequate numbers and normally
  functioning platelets, and a complete complement
  of coagulation factors.
• ANY ALTERATION IN THESE PERAMETERS CAN RESULT IN
  A BLEEDING DISORDER!!

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Coagulation

• Coagulation proceeds through a mechanical phase
  and a chemical phase.
• Each phase is counterbalanced by several
  thrombolytic factors to prevent excessive
  thrombosis.

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Coagulation contd

• Mechanical Stage (Primary Hemostasis)
• A blood vessel is ruptured or torn
• The exposed vessel subendothelium is a charged
  surface, consisting of collagen fibers, and
  platelets are attracted to this surface.
• Platelets congregate at the site of injury.
• Platelets undergo morphologic and physiologic
  changes, causing the platelets to adhere to each
  other as well as the blood vessel endothelium.
  This causes an initial plug of platelets.
• Platelets release the initiating factor for the
  chemical phase of hemostasis.

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Coagulation contd

• Chemical Phase (Secondary Hemostasis)

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Coagulation contd

• Chemical Phase (Secondary Hemostasis)
• Hemostasis relies upon a wide range of proteins
  called clotting factors and cofactors such as
  calcium and vitamin K.
• Each factor participates in a chemical reaction
  that serves to initiate the next reaction in the
  pathway.
• The end result of the coagulation cascade is the
  formation of prothrombin into thrombin which
  converts fibrinogen to fibrin.
• Each clotting factor is essential for the
  formation of fibrin.
• If any single factor is absent, the clotting
  cascade cannot be completed, and a fibrin mesh
  cannot be manufactured.

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Coagulation contd

• Chemical Phase (Secondary Hemostasis)
• Fibrin gathers around the platelets , capturing a
  mesh of RBCs and WBCs to complete the clot

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related
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The Formation of a Clot

1. Platets
2. Clotting Factors
3. Fibrinogen
4. Wbcs / Rbcs

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Fibrinolysis

• The final phase of hemostasis.
• Involves the breakdown / degredation of the
  fibrin clot by the body.

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• So what happens if there is an interruption with
  the hemostatic process?

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• Coagulopathy
• any disorder of blood coagulation.

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Coagulation Testing

• Evaluate specific portions of the hemostatic
  mechanisms.
• Some tests measure the mechanical (primary) phase
  of hemostasis, while others can measure specific
  parts of the chemical phase.
• All patients should be evaluated for coagulation
  defects before undergoing surgery.

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Coagulation Testing contd

• Blood samples should be collected carefully, with
  minimal tissue damage and minimal venous stasis.
• Never collect samples through indwelling
  cathethers.
• The preferred anticoagulant for coagulation test
  is sodium citrate.

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Coagulation Test contd

• Platelet Count manual platelet count is
  performed on a blood smear or on an automated
  analyzer.
• However, if a clotting disorder is suspected, a
  manual count is needed because the automated
  reader will misread clumped platelets.
• Platelets are counted at 400X in a hemacytometer.

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Hemostatic Defects

• Bleeding disorders may be caused by congenital or
  acquired defects in coagulation proteins,
  platelets, or the vasculature.
• Most bleeding disorders found in veterinary
  species are secondary to another disease process.

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• Signs of hemostatic deficiencies in coagulation
  proteins usually involve delayed deep tissue
  hemorrhage and hematoma formation.
• Signs associated with deficiencies include
• Petechia
• Ecchymotic Hemorrhage

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• The majority if congenital coagulation factor
  disorders involve a deficiency or abnormality of
  a single factor.
• Usually, signs of a congenital coagulopathy will
  be apparent before 6 mo of age.

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Von Willebrands Disease

• The most common inherited disorder of hemostasis.
• Normally, von Willebrands factor (vWF) promotes
  platelet clumping.
• With decreased amounts, or lack of this factor, a
  bleeding disorder results.
• Affected breeds Dobermans, GSD, Labs.
• 54 breeds affected total in the U.S.

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Von Willebrands Disease

• Dogs with this disorder SHOULD NOT BE USED FOR
  BREEDING!
• Predisposed breeds should be tested before
  breeding to ensure offspring will be clear.
• Special care must be take with surgical
  procedures.
• Clinical signs
• Easy bruising in predisposed breeds
• Prolonged bleeding during estrus
• Prolonged bleeding from venipuncture site

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Secondary Coagulation Disorders

• Result from decreased production or increased
  destruction of platelets.
• Nutritional deficiencies
• Liver disease
• Ingestion of certain medications or toxic
  substances.

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Secondary Coagulation Disorders contd

• Thrombocytopenia refers to a decreased number of
  platelets and is the most common coagulation
  disorder seen in small animal veterinary
  practice.
• The causes are often unknown.
• Infection with certain bacterial, viral, and
  parasitic agents can result in thrombocytopenia

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• .
• Thrombocytopenia can also occur as a result of
  bone marrow depression, which reduces the
  production of platelets or autoimmune disease
  that increases the rate of platelet destruction.
• The liver is the site of production of most
  coagulation factors, any condition that affects
  liver function can result in a coagulation
  disorder.

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Warafin Ingestion (Rat Bait)

• Inhibits the funciton of vitamin K function.
• Vitamin K is required for synthesis and
  activation of some coagulation factors. This
  creates a deficiency in several necessary
  components of the coagulation cascade.