Secondary Hemostasis Flashcards
What is involved in primary hemostasis?
vascular system and platelets
What is involved in secondary hemostasis?
Coagulation and fibrinolytic systems
What are the three separate processes in primary hemostasis?
Adhesion, aggregation, and secretion.
What is the by product of primary hemostasis?
An unstable platelet plug
What pathways are involved in a formation of a stable fibrin cloth around platelet plug?
intrinsic and extrinsic coag. pathways
Where does secondary hemostasis 3-D processes take place?
On the surfaces of platelets or on endothelial cell p.m. phospholipids
Can secondary hemostasis pathways occur on the appropriate kinds of lipids in the absence of a cell surface?
Yes, involved in in vitro clotting time assays. Discussed later
What do serine proteases do?
Cleave peptide bonds and have serine residue in active sites.
Zymogens are what and how do they work?
Inactive enzymes and must be modified in order to become active
The enzymes are of the coagulation cascades do what and require what cofactor?
The enzymes of the coagulation cascade do binding to the phospholipids and use calcium ions as a cofactor
What do cofactors do?
Bind to enzymes and make the enzymes more stable and reactive
What is another name for factor I
fibrinogen
What is another name for factor II?
Prothrombin
What is another name for factor III?
Tissue thromboplastin
What is another name for Factor IV?
Plasma calcium
What is another name for Factor V?
Labile factor
What is another name for Factor VII?
Stable factor
What is another name Factor VIII?
Antihemophilic factor
What is another name Factor IX?
Christmas factor
What is another name Factor X?
Stuart Prower factor
What is another name for Factor XI?
Plasma thromboplastin antecedent (PTA)
What is another name for Factor XII?
Hageman factor
What is another name for factor XIII?
Fibrin - stabilizing factor (FSF)
What is another name for Prekallikrein?
Fletcher factor (Pre - K)
What does HMWK stand for and what is another name for it?
Stands for High - Molecular - Weight Kininogen and another name is Fitzgerald factor
What is another name for platelet factor 3?
Platelet phospholipids
All the factors from coagulation cascade are involved in the formation of what?
fibrin clot
What test is used to test for the coagulation cascade pathway?
Activated partial thromboplastin time (APTT)
What factor initiates the intrinsic system cascade?
Factor XII aka Hageman factor
What does vascular damage do to the blood vessels?
Expose negatively - charged subendothelial tissue
What zymogen is attracted to negatively charged endothelial surface (damaged blood vessels)?
Factor XII aka Hageman factor. Once it attaches to the negatively charged endothelial surface it will expose its active serine center.
What are the four products of XIIa reactions?
- Prekallikrein (zymogen form)
- Plasminogen
- Factor XI
- C1
What does bradykinin do?
Increases local vasodilation and membrane permeability to increase local blood flow
The intrinsic pathway requires what as a cofactor?
HMWK (Homework) but really stands for High - molecular - Weight Kininogen
The “contact factor” complex is composed of what?
Factors XIIa, HMWK, and prekallikrein
Patient has pulmonary embolism (PE) and other thrombotic disorders. What could the patient be missing that leads to these conditions?
Doesn’t have or lacks enough factor XII. Teacher note: very little option for triggering fibrinolysis. Factor XII deficiency is the only coag. deficiency in which patients develop clots rather than bleeding.
Factor XI is activated by what factors and what does factor XI turn into after being activated?
Factor XI is activated by contact factors or XIIa and turns into XIa
Patient has a factor XI deficiency, what condition does the patient have?
Hemophilia C
Where is factor IX made?
Liver
Christmas factor is dependent on what?
Vitamin K dependent which modifies it so it can become functional
List vitamin K factors include what?
2, 7, 9, 10, C, S, & Z
What controls the production of factor IX?
X chromosome, therefore it is also sex - linked
A deficiency in Factor IX is a sign of what disease?
Hemophilia B, it also can go by the name Christmas disease
What is another disease that is X - linked coagulators besides hemophilia B? What factor is it deficient in?
Hemophilia A, its deficient in Factor VIII.
What does Factor IX need to do before it gets activated by factor XIa or VIIa?
It needs to bind to Ca2+ on a phospholipid surface(s)
Where or what produces factor VIII?
Hepatocytes (liver)
What is used to “carry” factor VIII?
vWF, each monomer of vWF has four functional domains that bind factor VIII, platelet glycoprotein Ib, V, IX, platelet glycoprotein IIb / IIIa, and collagen
Factor VIII:C combines with what to form an intrinsic tenase complex?
IXa, phospholipid and calcium
“intrinisc tenase complex” activates what?
Factor X to become Xa
A deficiency in factor VIII is called what?
Its called hemophilia A. Factor VIII decreased, vWF normal
A deficiency in vWF is called what in a patient?
vWD disease where Factor VIII decreased and vWF disease
What part of factor VIII can be assayed for immunologically?
The VIII:C portion and vWF portion
Whats the difference between Factor VIII and vWF?
Factor VIII
Activated by: Activated by Thrombin
Disease: X-linked (mostly male)
Origin: Made by liver
vWF
activated by: Release of plt granules & dmged endothelial tissue
Disease: Autosomal dominant or recessive (male & female)
Origin: Endothelial cells & megakaryocytes / plts.
What is factor VIII activated by?
Thrombin
In factor VIII deficiency disease, how is it inherited?
x - linked manifesting mostly in males
Where is factor VIII made?
Made by the liver
vWF is activated by what?
release of platelet granules & damaged endothelial tissue
How is the Von Williebrand’s Disease inherited?
Autosomal dominant or recessive, occurs in both female and males
Where is vWF made?
endothelial cells and megakaryocytes / platelets
Is Von Willebrand’s Factor stored in alpha granules?
fill later
What hemophilia is associated with factor VIII?
Hemophilia A
What hemophilia is associated with factor IX?
Hemophilia B
What hemophilia is associated with factor XI?
Hemophilia C
What test is used to examine the extrinsic pathway?
PT, prothrombin time test
Fill in the blank. Factor VII is made in the ____. It is dependent on _____ and activate by ______.
- Liver
- Vitamin K dependent
- Thrombin
What does factor VII require to form a complex to activate factor X?
Requires contact with Ca2+ and TF3 to form the complex.
What is another way factor VII can become activated besides coming into contact with Ca2+ and TF3?
When it comes across Vitamin K and thrombin.
Factori VII half life?
6 hours others are 12 to 72 hours.
Factor VIIa can activate which factor in the intrinisc pathway?
Factor IX
Where is factor III found?
In all tissue including WBC surfaces
Is Factor VIIa present on fibroblasts and smooth muscle cells?
Yes
When and where does TF3 circulate?
Cells / tissues are traumatized. TF3 begins to circulate in blood that makes it back to the body past the wound.
What factor activation begins the common pathway?
Factor X to factor Xa, Stuart Prower Factor
What factor begins the common pathway?
Factor X activation to Xa.
Where is Factor X made and is it dependent to vitamin K?
Liver and is vitamin K dependent
How is prothrombinase complex formed?
Xa + Va + Ca2+ + phospholipid creates prothrombinase complex
What does the prothrombinase complex do?
Covert prothrombin to thrombin by cleavage
What is factor 5 in the common pathway?
Its a coagulation cofactor. Its activity dimishes quickly at room temperature.
Where is factor II made, is it vitamin K dependent, and alternate name?
- Made in the liver
- Vitamin K dependent
- Also goes by the name prothrombin
What is the activated form of Factor II called and what activates Factor II?
- Thrombin (IIa). Its a major serine protease
- activated by prothrombinase complex
List the many functions of Factor IIa aka Thrombin.
- Enzymatically converts fibrinogen to fibrin
- Activates Factor XIII (fibrin stabilizing factor)
- Activates platelet aggregation
- Activates Factor V, VIII, and XI
- Activates Protein C
- Weak activation of factor VII to VIIa
Head Honcho protease of the coagulation pathway
What factor converts Fibrinogen to Fibrin?
Thrombin.
What is the reference range of fibrinogen?
200 - 400 mg/dL; Its the highest range of any clotting factors.
Where is fibrinogen made in the body?
The liver; From there it is absorbed, transported, and then released by platelets
What is the terminal substrate for the coagulation cascade?
Fibrinogen
What binds to platelet receptors before they start to aggregate?
Glycoprotein 2b3a
What happens to fibrinogen molecule when it is converted to fibrin?
Fibrinogen loses 4 small…
What does fibrin monomers do to each other?
Form a crosslink with each other to form a strong fibrin polymer (spontaneous polymerization) that can be described as a fishing net.
What factor stabilizes a platelet plug?
Factor IIIa (fibrin stabilizing factor)
What does congenital hypo- or afibrinogenemia cause?
Severe bleeding caused by failure to form fibrin clots (just platelet plugs are formed)
Where is factor XIII made and how is it activated?
Made in the liver; depends on thrombin for activation
What does Factor XIIIa do?
Form crosslinks polymerized fibrin (by transferring amino acids) stabilizing fibrin.
Factor XIIIa do for the fibrin clot?
- give mechanical rigidity
- Protects clot from lysis by plasmin (activate form of plasmino gen)
When should a person be tested for factor XIIIa?
Tested individually past the point of clot formation
What are the functions of factor IV?
- Acts as the mediator of platelet activation
- Helps bind vitamin K - dependent coagulation factors to phospholipids like TF3 & PF3
Describe in vitro anticoagulation.
Chelation of calcium ions so it is unavailable for coagulation cascade to use. This occurs throughout the tube where as in the body it is a local phenomenon.
Where does calcium ions come from for the coagulation cascade to use?
From plasma circulating and by activated platelets from their dense granules.
Prekallikrein’s alternate names, activated by what, where is it found?
- Pre - K or Fletcher Factor
- Factor XIIa and turned into kallikrein
- Circulates in plasma as a complex attached to HMWK
Where is prekallikrein made and what kind of protease is it?
Liver; a serine protease
What factors make up the contact factors?
HMWK, XIIa & Prekallikrein
What is HMWK and function?
A cofactor made by liver.
1. Acts as a cofactor to accelerate activation of Factor XI by Factor XIIa
2. Acts as a substrate for kallikrein in production of kinins.
What is another name for HMWK?
Fitzgerald factor
Is platelet facto 3 (PF3) the same as Tissue factor 3?
No, but they have similar functions
What does PF3 do?
Phospholipid that supports fibrin clot formation
Where does TF3 come from?
Comes from damaged endothelial cells
What does Protein C inhibit?
Circulates in an inactive zymogen. Activated by thrombin and inactivates VIII:C and Va in the presence of cofactor Protein S
Protein S is made where? Vitamin - K dependent?
Made in the liver and is vitamin - K - dependent
Protein S circulates in what kind of forms?
Bound form - to complement control protein, C4b - binding protein; cannot participate in pathway.
Free form serves as APC cofactor.
Describe Protein Z
Lacks an activation site and functions along with ZPI to inactivate Xa
Describe Tissue Factor Pathway Inhibitor (TFPI) origin and activates what factor.
Made by endothelial cells and expressed on platelets. Combines with Factor VIIa to activate factors IX and X.
Describe tissue factor pathway inhibitor (TFPI)’s inhibiting coagulation
- Bind and inactivate Factor Xa
- TFPI:Xa complex binds to TF:VIIa, and prevents further activation of X and IX
What are the naturally occurring anticoagulants?
- Antithrombin (AT-III, AT) - Major serine protease inhibitor (SERPIN)
- Protein Z - dependent protease inhibitor (ZPI)
- Protein C inhibitor
- Alpha - 2 - macroglobulin
What does antithrombin do and requires what?
- Binds and neutralizes thrombin and factors IXa, Xa, XIa, and XIIa
- Requires heparin (increased inhibitory effect of AT by 1000 fold)
Protein Z - dependent protease inhibitor inhibits whats?
- Factor Xa when combined with protein Z
- Inhibits factor XIa independently (2x with heparin)
Protein C inhibitor inhibits what? Is it procoagulant or anticoagulant?
- Binds to heparin and inhibits APC, thrombin, factor Xa, factor Xia, and urokinase
- Its both a procoagulant and anticoagulant
Alpha - 2 - macroglobulin
Inhibits plasmin and in a minor inhibitor of thrombin
List acquired circulating anticoagulants
Coumarin/ coumadin / warfarin, heparin, Unfractionated Heparin, Low Molecular Weight Heparin (LMWH), Hirudin, Argatroban, Plavix, Reopro
How does coumarin, coumadin, wafarin derivatives prevent coagulation?
-Prevents efficient production of prothrombin family of coagulation factors, including proteins C & S. It interferes with vitamin K’s role in this process.
-Inhibition takes time to take effect and protein S & C are turn off first.
Note: 1st few days of OAC therapy patient is hypercoagulable & to be covered by temporary heparin therapy to prevent possible thromboembolism.
What can a person eat to reduce OAC’s effect?
Eat more dietary vitamin - K
How does heparin work to prevent coagulation?
Acts as an allosteric activator of AT. Heparin activates antithrombin to neutralize serine proteases (IIa, IXa, Xa, XIa, and XIIa). It brings AT close enough to thrombin that it activates the thrombin - antithrombin reaction at 1000x greater rate. Sourced from porcine intestine or bovine lung.
What are the two types of heparin?
- Unfractionated heparin more than 17 saccharides
- Low Molecular Weight Heparin less than 17 saccharides
What should be given to a patient with heparin - induced thrombocytopenia?
Give patient protamine sulfate
What are three ways to monitor unfractionated heparin (UFH)?
APTT - activated partial thromboplastin time
Whole blood activated clotting time (ACT)
Chromogenic anti - Xa immunoassay
What is the range of PTT?
0.3 to 0.7 anti-factor Xa U/mL (Brill - Edwards Method)
How would a therapeutic range for PTT management of UFH therapy be establish?
Collect 50 or more patient samples and run PTTs on all samples. Then run chromogenic anti - factor Xa assays on all and graph results on a linear graph.
What is chromogenic anti - Xa heparin assay?
Preferred over ACT for its stability and reproducibility.
Test plasma mixed w/ protease (Xa) and incubated for several minutes and chromogenic substrate is added. Degree of hydrolysis is measured by colored end product, and inversely proportional to activity of AT - Heparin complex in plasma.
How is LMWH monitored?
Cannot be monitored by PTT. Chromogenic anti - Xa assay is used instead.
Describe Hirudin and when is it used?
- Derived from leeches. Its a direct thrombin inhibitor.
- Its monitored by PTT, prolongs PT, thrombin time & ACT
- 30 minute half life
- Used on HIT patients during 1st, 3 - 5 days of OAC administration
Describe argatroban, when is it used?
- Direct thrombin inhibitor
- Only 51 minute half life
- Used on HIT patients during 1st, 3 - 5 days of OAC administration
Describe Plavix aka clopidogrel bisulfate
- Oral ADP receptor antagonist
- Useful for MI prevention & ACS (acute chest syndrome, used to be called unstable angina) management
Describe Reopro (abciximab)
- Given IV
- Must be monitored
- Intereferes with glycoprotein Gp2b3a receptor’s ability to bind to fibrinogen
What is fibrinolysis? When does it start?
Systematic hydrolysis of fibrin by plasmin. Starts within an hour or so of fibrin formation
What is plasminogen?
Inactive form. It’s a single - chain protein with five glycosylated loops termed “kringles” enable binding to fibrin during polymeration. It can bind to plasma alpha 2 - antiplasmin, collagen, kininogen, and cell surface receptors too.
Where is plasminogen made?
Liver
How is plasminogen converted to plasmin?
When cleaved by tissue plasminogen activator (TPA) and urokinase.
What is tissue plasminogen activator?
Made by endothelial cells. It hydrolyzes fibrin bound plasminogen and initiates fibrinolysis by forming covalent lysine bonds w/ fibrin during polymerization
What is urokinase?
Secreted by epithelial cells, monocytes, and macrophages. Its main job is degrading extracellular matrix.
What is plasmin’s function?
- Degrade fibrinogen and fibrin.
- Inactivation of Factor V and VIII:C
- Direct anti-aggregation effect on platelets
What does plasmin break fibrin into?
Breaks the fibrin polymers into a monomer form known as fragment X. A fragment X consist of an E domain and 2 D - domains.
Fragment X can be broken down further into what?
Breaks into Fragment Y ( 1 X E - Domain & 1 X D - Domain),
Fragment E is one E domain,
Fragment D is one D domain,
D - dimer is two D - fragments linked together.
What are fibrin degradation products?
Fragment Y, Fragment E, Fragment, D, D - Dimer, E Domain, and D domain.
What kind of effect does fibrin degradation products have on the coagulation process?
Anticoagulating effect
1. Inhibit process of fibrin polymerization
2. Competitive inhibition of thrombin
3. Prolong TT (TCT) test
Are fibrinogen split products the same as fibrinogen degradation products?
Yes
What are ultimate products when plasmin degrades fibrinogen and fibrin poymers?
E and D domains
What are the ultimate products when plasmin degrades crosslinked fibrin?
D - dimer and E fragment
Plasminogen Activator Inhibitor - 1 (PAI - 1) inhibits plasminogen how?
Prevents TPA and urokinase from activating plasminogen.
When does PAI - 1 exceed TPA levels?
When endothelial cells are activated
Alpha 2 - antiplasmin binds to what irreversibly?
Irreversibly binds to free plasmin
