Hemostasis - Ex 6 Flashcards
Factors of Intrinsic Pathway (4)
VIII
IX
XI
XII
Factors of Extrinsic Pathway (1)
VII
Factors of Common Pathway
X
V
II
I
What is the importance of Factor XIII?
Solidifies fibrin clot!
Main source of Coag. Factors
LIVER!
*MOs: II, V, VII, X
Factor III
aka Tissue Thromboplastin
*Found in fibroblasts, sm muscle cells, and endothelial cells
**Phospholipid & TF = Factor III
Vit K dependent Factors
II, VII, IX, X
*Vit K activates these factors
Main Anticoagulation protein
Antithrombin (70%)
This is the ONLY anticoagulant. protein we measure
What does Antithrombin inactivate?
Thrombin XIIa XIa Xa IXa
Glomerulus and Antithrombin
Antithrombin can pass through glomerulus when damaged –> This decreases antithrombin levels –> patient is now more susceptible to Thrombosis
Fibrinolysis
Conversion of plasminogen to plasmin by:
Factor XII and tPA
Tissue plasminogen activator - therapy
Used clinically for strokes
- tPA will artificially force clot breakdown
Fibrinolysis - Simplified
Plasmin breaks down fibrin or fibrinogen into:
- D-Dimers
* *Fibrin only - Fibrin(ogen) Degradation Products (FDPs)
Thrombocytopenia - Differentials (3)
- Destruction (most common)
- Consumption
- Decreased production
Thrombocytopenia
Disorder of primary hemostasis –> see petechia on mucosal surfaces and membranes
DIC
Cause of thrombocytopenia - consumption
- Massive activation of clotting factors
- Rapid consumption of clotting factors –> leads to bleeding
* *Clotting to death and bleeding to death at the same time**
*DIC is a red flag for a severe underlying disorder –> it is never a primary disorder
DIC - Causes
- Extensive Tissue Damage
- heat stroke
- pancreatitis
- severe hypoxia
- Endotoxemia/Septicemia
- IMHA
- Neoplasia (procoagulant proteins)
- Vascular disease
Easiest way to remember DIC? (Lab Values)
EVERYTHING is abnormal!
Liver failure
Liver is source of clotting factors –> damaged liver –> decreased production of factors –> coagulopathy
Bile Duct Obstruction
Bile is required to absorb fat –> Via K is fat solute –> without fat, there is a Vit K deficiency that can reduce coagulation factor activity
Name 7 Lab Evaluations of Hemostasis
- Platelet count
- Bleeding time
- Activated clotting time (ACT)
- Activated partial thromboplastin time (APTT)
- One-stage prothrombin time (OSPT or PT)
- Fibrinogen (Thrombin Time)
- von Willebrand factor (vWDF)
Platelet count
Estimation from a blood film
Automated
Bleeding Time
Cut buccal mucosa and see how long it takes to clot
Tests of Intrinsic Pathway
APTT and ACT
Tests of Extrinsic Pathway
OSPT (aka PT)
Which of the tests uses whole blood?
ACT
*Thrombocytopenia can cause erroneously prolonged clotting times
Quantitative Fibrinogen
Measure of fibrinogen
- Excess thrombin is added to diluted plasma
- Rate of fibrinogen to fibrin is measured
- Time to “clot” is indirectly proportional to fibrinogen concentration
How do we measure fibrinolysis?
D-Dimers
