Coagulation Cascade Flashcards
Plasma
Contains many substances dissolved in water
Component: proteins + water + other solutes (includes electrolytes)
Plasma proteins
Albumin (most abundant; 57% of plasma proteins)
Globulins (HDL, prothrombin, hormone-transporting proteins)
Clotting proteins (I.e. fibrinogen)
Blood cellular components
Erythrocytes, leukocytes, neutrophils, eosinophils, basophils, monocytes/macrophages, lymphocytes, natural killer cells, platelets
Platelets
Not true cells (cell fragments)
Contain cytoplasmic granules which can release adhesive proteins, and coagulation/growth factors in response to vessel injury
Platelet count
Normal: 150,000-400,000
Thrombocytopenia: <100, 000
Additional platelets are stored in the spleen
Platelet aggregation process
Blood vessel damage->increased platelet adhesion->platelets release contents of granules (degranulation)->platelets aggregate by adhering to the vascular wall and other platelets->platelet plug formed (temporary)->clotting cascade initiated/activated
Blood clot
Meshwork of fibrin strands, platelets, and trapped cells; blood clot plugs the damaged vessel and stops the bleeding (enables hemostasis); blood clots stabilize the platelet plug
Platelets and blood clots
Platelets are the primary activators of blood clot formation
Thrombin
Active enzyme form of prothrombin (a plasma protein)
Why is thrombin so important?
Catalyzes the conversion of fibrinogen to fibrin, and fibrin is an important component of blood clots
Blood clot components
Fibrin mesh
Platelets
Trapped blood cells
Intrinsic clotting pathway
Involves factors:
12, 11, 9, 10, 2, and 1
Factor II
Prothrombin
Factor IIa
Thrombin (active)
Factor I
Fibrinogen
Factor Ia
Fibrin
Extrinsic clotting pathway
Factors involved:
3, 7, 9, and 10
Factor III
Tissue factor
Factor Xa
Catalyzes the conversion of prothrombin to thrombin; thrombin then catalyzes the formation of fibrin; factor common to both the intrinsic and extrinsic pathway
Intrinsic vs. extrinsic clotting pathway
Blood clot formation occurs primarily through the extrinsic pathway but the extrinsic pathway can trigger the intrinsic pathway for MORE thrombin formation; extrinsic pathway is activated first then the intrinsic is turned on
Clotting factors activated by thrombin
5, 7, 8, 11, and 13
Factor XIII
Activated by thrombin; stabilizes the fibrin network by forming cross links between fibrin strands
Serum
Plasma minus clotting factors
Antithrombin III
Circulating inhibitor of thrombin (inhibits clotting)
Tissue factor pathway inhibitor
Inhibits factor Xa (factor that converts prothrombin to thrombin)
Fibrinolytic system
System that dissolves an already formed clot; involves activation of plasminogen to plasmin (active); plasmin digests fibrin; t-PA is an example of a plasminogen activator
Goals of coagulation therapy
Prevent clot formation, break apart existing clots, increase circulation/perfusion, decrease pain, prevent further tissue damage
Greatest concern of anti-coagulants?
Bleeding; side effect of ALL anti-coagulants; bleeding can be internal or external; know sites at risk for bleeding; monitor HgB/HCT/vitals
Anti-coagulants
Inhibits the action or formation of the clotting factors; PREVENTS the formation of clots; interferes with the clotting cascade
Anti-platelets
Inhibit platelet aggregation and prevent platelet plug formation; best for preventing heart attacks and strokes; remember platelet aggregation occurs before the coagulation cascade
Heparin MOA
Activates antithrombin III which indirectly inactivates clotting factors 2 (thrombin) and 10; inactivation of these clotting factors prevents blood clot formation; heparin inhibits fibrin formation (because thrombin is inactivated)
heparin that only inactivates factor Xa and NOT factor II (thrombin)
Low molecular weight heparin enoxaparin (Lovenox)
heparin indications
Conditions requiring quick anti coagulation; evolving stroke/PE/massive DVT; adjunct therapy for patients having open heart surgery or dialysis; low-dose therapy for post-op DVT prophylaxis/prevention; to treat disseminated intravascular coagulation
Heparin nursing considerations
Only given parenteral (IV/SUBQ), can be given 5000 U injection 2-3x a day or as an IV drip with bolus (usually weight based)
Heparin nursing considerations
Starts working quickly (20-30 minutes for SUBQ; immediately for IV); antidote is protamine sulfate, use cautiously in patients with spinal/epidural anesthesia; high risk (must double check other another RN prior to rate changes/bolus)
Heparin onset (SUBQ)
20-30 minutes
Heparin onset IV
Immediate