Lecture 22: Anticoagulants and Hemostatic Agents Flashcards
A functional clotting system depends on what 3 things
- Production of clotting factors
- Functional platelets
- Fibrinolysis
Describe the intrinsic coagulation pathway to the common pathway
- Factor XII
- Factor XI
- Factor IX
- Factor VIII
- Factor X (start of common pathway), forms complex with factor V
- Factor II-thrombin
- Factor I-fibrinogen
- Clot formation
Describe the extrinsic pathway to the common pathway
- Tissue factor
- Factor VII
- Factor X, forms complex with factor V (start of common)
- Factor II-thrombin
- Factor I- fibrinogen
- Clot formation
What are the 4 vitamin K dependent clotting factors
II, VII, IX, X
What are some indications for anticoagulants in hyeprcoaguable/ thromboembolic states
- Cats with hypertrophic cardiomyopathy
- Dogs with IMHA
- Dogs with Cushing disease
- Animals with acute phase inflammation
- Protein losing nephropathy
How do cats with HCM initiate hypercoaguable states
Form blood clots in Left atrium—> left ventricle and can enter circulation causing saddle thrombi or even travel to the brain
How do dogs with IMHA cause hypercoaguable states
Activate coagulation system
How do animals with Cushing disease cause a hypercoaguable state
More fibrinogen floating around
How do animals with acute phase inflammation cause hypercoaguable states
More clotting factors
How do animals with protein losing nephropathy cause hypercoaguable states
Podocytes damaged causing anti-thrombin III to leak out
Antithrombin III important to keep thrombin from spontaneously going off in blood
What are some indications for coagulants in hypocoaguable states
- Post sx trauma
- Intoxication
- Genetic bleeding disorders
- Liver dysfunction
- Liver failure
How does liver dysfunction and failure lead to hypocoaguable states
Can’t make clotting factors
What part of coagulation system does warfarin sodium impact
Production of clotting factors
What is warfarin sodium indicated for
Prophylactic treatment of thrombotic conditions (HIGHLY CONTROVERSIAL)
What is the mechanism of action for warfarin
Blocks vitamin K reductive so can’t properly form clotting factors
Warfarin is associated with ___ with anemia
Fatal hemorrhage
___ can form in any system when patient is treated with warfarin sodium
Hematomas
Warfarin sodium requires frequent monitoring of ___
Prothrombin time
T or F: dogs easily develop tolerance with warfarin sodium
True
Where in the coagulation system does vitamin K1 impact
Clotting factors- promotes clotting
What are some indications for Vitamin K1
- Rodenticide or moldy sweet clover
- Prolonged sulfonamide to of birds with coccidosis
- Congenital vitamin k dependent coagulopathy
- Porcine hemorrhagic syndrome
Will vitamin K1 help with chronic liver failure, why or why not
It won’t, liver failure patients don’t make clotting factors so vitamin K can’t activate them
What are the pharmacodynamics of vitamin K
Conjugated to newly synthesized y-glutamyl carboxylase in liver by enzyme dl-diaphorase that makes new y-glutamyl carboxylase which is needed to form clotting factors
What is the Vd of vitaminK1 like
Low, binds to chylomicrons and concentrates in liver
What is enoxaparin sodium and dalteprin sodium
Low molecular weight heparin fraction
Where does heparin, enoxaparin sodium and datleparin sodium act in coagulation system
Prevent clotting factors from clotting
what is the reversal agent for heparin
Protamine sulfate
IM and deep SQ administration of heparin can cause __
Hematomas
Heparin requires the presence of __ to work
Anti-thrombin III
What is the bleeding risk associated with heparin use
10% of dogs with IMHA (promotes hypercoagulation) had bleeding incidents after treatment with low molecular weight heparin fraction
Nonspecific binding of heparin to platelets can cause what
- Immune mediated thrombocytopenia and platelet activation
- RBC agglutination in horses
What is the mechanism of action of rivaroxaban
Competitively inhibits Factor Xa
T or F: rivaroxaban, unlike heparin, does not require anti-thrombin III to work
True
Where in the coagulation system does acetylsalicyclic acid affect
Platelet function
What is the pharmacodynamics of acetylsalicyclic acid
Irreversible inhibition of COX1 preventing thromboxane A2 (TxA2) production
What are some toxicities associated with acetylsalicyclic acid
- Overdose- life threatening metabolic acidosis, depression, vomiting, hyperventilation, hyperthermia
- GI ulceration (block PG synthesis)
- Nephrotoxicity (especially in horses with colic or on antibiotics)
What are some contraindications for acetylsalicyclic acid
- Cats
- Bleeding disorders
- Kidney insufficiency
- Liver insufficiency
- Upcoming sx
Where in coagulation system does clopidogrel bisulfate act
Platelet formation
What are the pharmacodynamics of clopidogrel bisulfate
Irreversible inhibition of the platelet ADP receptor
In order for clopidogrel bisulfate to be absorbed it requires a __ pH
Low
What are the general pharmacodynamics of topical platelet forming drugs
- Activate patient platelets
- Inject fibrinogen and activating agent to cause quick clot/gel formation
What is collasate
Topical type I collagen foam to activate platelets
How does collasate work
Activates platelets by binding to their collagen receptor
At what point in the coagulation system does tissue plasminogen activator act
Fibrinolysis
What is tissue plasminogen activator indicated for
- Pulmonary thromboembolism
- Arterial thromboembolism
What are 2 examples of anti-fibrinolytic drugs
- Aminocaproic acid
- Tranexamic acid
What is aminocaproic acid used for
Post surgical bleeding in dogs and guttural pouch bleeding in horses
What is tranexamic acid used for
Post sx bleeding in dogs and cats
T or F: tranexamic acid is more effective than aminocaproic acid
True
Are the following hemostatics or anticoagulants: collasate, vitamin K, aminocaproic acid, tranexamic acid
Hemostatics
Are the following hemostatics or anticoagulants: tissue plasminogen activator, clopidogrel, aspirin, heparins, rivaroxaban, warfarin
Anticoagulants
