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COAGULATION / COAGULOPATHY
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Goal of Caoagulation is to form a localizeed fibrin meshwork. Three components necessary for normal coagulation are intact vasculature (trauma, vasculitis), coagulation factors (DIC, rodenticide, liver failure, congenital), and platelets (aspirin, NSAIDs). Most common bleeding problems are dt thrombocytopenia and coag factor deficiency.
Intrinsic pathway
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Starts w/ exposure to abnormal surface. Factors XII, XI, IX, VIII. Factor VIII deficiency is hemophilia A, most common inherited bleeding deficiency in dogs and cats. X-linked, females are asymptomatic carriers, males are affected. Factor IX deficiency is hemophilia B.
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In cats, Factor XII deficiency commonly recognized but rarely causes clinical bleeding.
Extrinsic pathway
- Starts with tissue injury, factor III (Thromboplastin) released. Factor VII.
Common pathway
- Factor V, X, prothrombin to thrombin, fibrinogen to fibrin.
ATIII
- Thrombin antagonist. Acts on II, IX, X, XI, XII.
Vitamin K dependent factors
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II, VII, IX, X. Vita K antagonism or deficiency assoc with rodenticide toxicity (warfarin, coumarin), malabsorption, heriditary (devon rex cats), and hemorrhagic porcine stress syndrome. Expect prolonged clotting times (PT, then PTT). PIVKA. If suspicious, treat with Vitamin K and watch for improved clotting times with in 24-48 hrs.
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Vascular or platelet abnormalities
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Coagulation Factor Abnormalities
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Petechiation
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Petechiation rare
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Hematomas rare
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Hematomas common
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Multiple sites common
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Frequently localized
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Mucosal bleeding common
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Mucosal bleeding can occur
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Hemarthrosis rare
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Hemarthrosis common; delayed onset of bleeding, then profuse rebleeding
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Prolonged bleeding from cuts
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Purpura and ecchymoses rare
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Purpura and ecchymoses common
Body cavity hemorrhage rare
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Big body cavity hemorrhage common
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Test of Vasculature
Test of Platelets
- Need good,clean stick. Platelet count, blood smear, platelet aggregation, bleeding time test.
Test of Coagulation Factors
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Intrinsic system with ACT, PTT (XII, XI, X, IX, VIII, II or I). Extrinsic system with PT (VII, X, V, II, I), also good test for vita K antagonism since factor VII has shortest t½ of vita K dependent factors.
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Fibrinogen and FDP assay for DIC, vWD assay in certain breeds (DPs), PIVKA (glorified PT, rodenticide testing).
Inhibitors of Coagulation
- ATIII, aspirin, EDTA (binds divaalent Ca ions), heparine (activates ATIII), dicoumarol (Vitamin K antagonist, rodenticide).
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Participants