PP: Haemostasis Flashcards
Define haemostasis.
A process which causes bleeding to stop, meaning to keep blood within a damaged blood vessel.
Describe the principles of normal haemostasis.
- Prevents bleeding
- Prevents unnecessary coagulation and allows blood to flow
Describe the critical steps in the clotting cascade.
Prothrombin—>thrombin
Firbrinogen—> fibrin
Explain the tests in a coagulation screen.
APPT measures the activity of the intrinsic pathway. Therefore, prolonged APPT is seen in patients with a deficiency in intrinsic clotting factors e.g. (XII, XI, IX & VIII)
PT measures the activity of the extrinsic pathway. Therefore, prolonged PT is seen in patients with a deficiency in extrinsic clotting factors e.g. VII
Describe the common causes of thrombocytopenia.
- Patients without a spleen
- Aspirins
- Pregnancy
- Cancer
- Alcohol abuse
Explain the differences
between thrombocytopenia caused by marrow failure and thrombocytopenia
caused by peripheral destruction.
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Explain the mode of inheritance of haemophilia A.
X-linked
Explain the mode of inheritance of von-Willebrand disease.
Autosomal dominant
Explain the basic clinical and laboratory abnormalities
of patients with haemophilia A.
- Lack of factor 8
- Bleeding into muscles and joints
Explain the basic clinical and laboratory abnormalities
of patients with von-Willebrand disease.
- Abnormal platelet adhesion to vessel wall
- Reduced VWF which carries FVIII so this too can be low
- Skin an mucous membrane bleeding
- Prolonged bleeding after trauma
Explain the causes of disseminated intravascular
coagulation.
- Cancer, especially certain types of leukemia
- Infection in the blood, especially by bacteria or fungus
- Liver disease
- Pregnancy complications (such as placenta that is left behind)
- Massive tissue injury
How do you diagnose DIC?
- Platelet count.
- Global clotting times (aPTT and PT)
- One or two clotting factors and inhibitors (eg, antithrombin)
- Assay for D-dimer or FDPs.
How do you treat DIC?
- Plasma transfusions to replace blood clotting factors if a large amount of bleeding is occurring.
- Blood thinner medicine (heparin) to prevent blood clotting if a large amount of clotting is occurring.
What is Von Willebrand factor?
Involved in platelet adhesion to the vessel wall, platelet aggregation and also carries FVIII
What is thrombocytopenia?
Thrombocytopenia is a condition in which you have a low blood platelet count.
