Coagulation Modifiers Flashcards
3 processes involving blood coagulation
- Vasoconstriction
- Platelet clumping
- Cascade of clotting factors (coagulation)
First reaction to blood vessel injury.
- If injury is small, this can close the blood vessel and arrest the bleeding and allow the vessel to heal.
Vasoconstriction
- Injury to blood vessel exposes collagen and other substances under the endothelial lining of blood vessels.
- Platelets stick to site of injury
- Collagen and platelets release chemicals (serotonin, adenosine di-phosphate and thromboxane A2 etc.) which causes vasoconstriction and more platelets to attach.
Platelet Aggregation
If platelet plug and vasoconstriction not enough to seal injury, ______ process may occur.
Coagulation
2 pathways of coagulation
- Intrinsic Pathway
2. Extrinsic Pathway
Coagulation Pathway.
a. XII is activated to become XIIa
b. XIIa activates XI which leads to the activation of other factors in the pathway until the conversion of prothrombin into thrombin is reached.
c. Thrombin activates fibrinogen, then fibrinogen activates fibrin that forms a clot (thrombus) into the vessel. The thrombus (platelet + fibrin) then seals the blood vessel.
Intrinsic Pathway
Coagulation Pathway.
- Blood leaked out of the blood vessel into surrounding tissue also form a clot.
- Injured cells release tissue “thromboplastin” (tTP), which activates clotting factors in the blood and starts clotting cascade to form a clot on the outside of the blood vessel.
- The injury vessel is now vasoconstricted and has a platelet plug and clots on both sides of the injury.
Extrinsic Pathway
A chemical substance in the blood in which comes in contact with injured blood vessels.
Hageman Factor, XII
Chemical released by injured cells which activates clotting factors in the blood and starts clotting cascade to form a clot on the outside of the blood vessel.
Thromboplastin (tTP)
A clot that consists of platelets and fibrin that seals the blood vessel.
Thrombus
2 factors that inhibit blood clotting in the blood plasma.
- Anti-thrombin
2. Plasminogen
Factor that prevents the formation of thrombin.
Anti-thrombin
a. Activators converts plasminogen to plasmin.
b. Plasmin targets fibrin and dissolves clot.
The Plasminogen Mechanism
Activators that converts plasminogen to plasmin. (4)
ADH, NE, urokinase, streptokinase
A genetic deficiency or absence in clotting factor VIII, which causes increased bleeding and usually affects males.
- Regular drug Tx not required, concentrated mixture of factor use of severe bleed or bruising occurs.
Haemophilia A
Factor IX deficiency - low to absent.
Haemophilia B aka Christmas Disease
Clotting disorders can also be present in the absent or deactivation of what certain vitamin?
Vitamin K deficiency
The process that stops bleeding after injury to blood vessel.
Hemostasis
The process of formation of a fibrin blood clot (thrombus)
Thrombosis
A small fragment of a thrombus that breaks off and circulates until it becomes trapped in a capillary causing either ischemia or infarction to the area distal to the obstruction.
Embolus
Agents that inhibits the action or formation of clotting factors and therefore prevents clots from forming. No effect on clot that is already formed. For unstable angina, MI, atrial fib, indwelling devices. Reduce risk of venous thrombi (composed of fibrin and RBC) Most common is Heparin and Warfarin (Coumadin)
Anticoagulant
Agents that prevent platelet plugs from forming by inhibiting platelet aggregation. Reduce risk of arterial thrombi (due to platelet aggregation)
Anti-platelet agent
Agents that breakdown preformed clots.
Thrombolytic Agent (fibrinolytics)
Agents that promote blood coagulation and help in the management of conditions in which excessive bleeding would be harmful.
- Stop bleeding
- Prevention and Tx of excessive bleeding resulting from systemic hyperfibrinolysis or surgical complications such as repeated coronoary bypass surgery
Haemostatic Agent (antifibrinolytics)
Diseases associated with abnormal clotting within blood vessel.
thrombo-embolic diseases
Used to diagnose presence and aetiology of a thrombus and an embolism.
- Physical Exam
- Client History
- Doppler Ultrasound
- Phlebography
- Radiolabel fibrinogen studiees
- Angiogram
Lab tests for Heparin that are used to measure the effect of the drug on clotting. (2)
APTT (activated partial thromoplastin time) and/or ACT (activating clotting time)
Lab tests for “Oral Anticoagulants” that are used to measure the effect of the drug on clotting. (2)
PT (prothrombin time) or INR (international normalized ratio)
Amount of prothrombin in the blood is assessed by determining __________
Prothrombin Time (PT)
- Thromboplastin and Ca+ are added to a sample of the patients plasma and to a control sample simultaneously.
- The amount of time require for clot formation in both samples is measured.
- Prolonged indicates deficiency of one of the factors.
- Normal time is 11 to 12.5 s (vary from lab to lab)
Prothrombin Time
Test that is used to detect coagulation defect of the intrinsic system.
- Activated partial thromboplastin is added to a sample of the patients blood plasma and a control sample.
- Time required for formation of clot is measured.
- Delayed clotting time suggests abnormality in one or more factors of intrinsic system.
- Further tests require to identify specific abnormal factor.
- Used in detecting haemophilia and monitor effect of heparin.
- Normal 60-85 s after addition of reagent and Ca++ to blood (vary from lab to lab)
PTT Test
Test that determines the efficacy of various clotting factors.
- Normal time 32-51 s (vary from lab to lab)
APTT (activated partial thromboplastin time)
The prothrombin time ratio that would have been obtained if a standard reagent in the PT determination.
- Patient prothrombin time/ mean of prothrombin time of reference interval.
- a laboratory measurement of how long it takes blood to form a clot. It is used to determine the effects of oral anticoagulants on the clotting system.
International Normalized Ratio (INR)