Haemostasis Flashcards
what is haemostasis
Haemostasis: blood (haem) stop/stand still (stasis)
The haemostasis is strictly controlled
what are the 5 major components of the haemostatic system?
- Blood vessels
- Platelets
- Coagulation factors
- Coagulation inhibitors
- Fibrinolysis
what is primary haemostasis?
- Platelets respond to the vessel wall
injury - Platelets adhere to the vessel wall
- A primary platelet plug is formed
what is secondary haemostasis?
- Activation of the intrinsic and
extrinsic coagulation pathways - Activation of the common pathway
- Fibrin strand formation and
strengthening of the platelet plug
describe Blood Vessels in Haemostasis
describe Von Willebrand Factor (vWF)
discuss characteristics of Platelets
describe platelet storage granules
describe the primary haemostasis process
what are the results of primary haemostasis?
Primary haemostasis forms a temporary and weak platelet plug
Unstable and needs strengthening
secondary haemostasis
what is the need for secondary haemostasis?
A weak platelet plug needs strengthening by coagulation
factors (secondary haemostasis)
what is secondary haemostasis strengthened by
Coagulation factors are mostly proenzymes (zymogens)
where are most coagulation factors synthesised?
liver
what do proenzymes require to carry out their function
Proenzymes require activation to carry out their function
* Active form of a coagulation factor is denoted ‘a’
what are the four stages of haemostasis?
Explain the Coagulation Cascade
explain the extrinsic pathway
explain the intrinsic pathway
explain the common pathway
What happens to the clot afterwards?
Why do we not get clots all the time?
Why do we not get clots all the time?
When to get tested?
- Unexplained or excessive bruising or prolonged bleeding,
either spontaneously or from injuries or surgery. - For women and girls who experience very heavy periods.
- Relative with a known hereditary coagulation factor deficiency.
- To follow up treatments after receiving a diagnosis to see that
your treatment is working. - Other medical conditions that affect coagulation factors.
- As part of investigations for Thrombophilia (increased clotting).
Tests used to evaluate clotting and bleeding
- Standard tests
- Full blood count (FBC)
- Blood film
- Coagulation tests
- PT, APTT and TT
- Analysis of clotting inhibitors like Protein C and Protein S
- Platelet function tests
- PFA-100 and lumi-aggregometry
- Flow cytometry for receptor expression
- A test to rule out blood clots in the body
- D-dimer
what are the Specimen Requirement?
Laboratory Diagnosis
Prothrombin Time (PT)
Activated Partial Thromboplastin Time (APTT)
Thrombin Time (TT
fibrinogen quantification
Fibrinogen quantification is a laboratory test that measures the amount of fibrinogen in the blood. Fibrinogen is a protein that is essential for blood clotting. The normal fibrinogen levels for an adult range between 200 and 400 milligrams/deciliter. The test measures fibrinogen levels as grams per litre. A typical fibrinogen level is between 4 grams per litre or 200 to 400 milligrams per deciliter. The Clauss assay is a functional test that measures the time taken for plasma to clot in a high concentration of thrombin, with a comparison against a reference plasma calibration curve. It is the gold standard for fibrinogen quantification
vWF test
Measuring Protein C
Measuring Protein S
Measuring platelet function
Flow cytometry
Summary: Laboratory Tests
- The coagulation cascade can be evaluated with multiple tests:
- PT – extrinsic and common pathway
- APTT – intrinsic and common pathway
- TT – functional fibrinogen
- Protein C and Protein S – Protein deficiency that leads to blood clots
- Platelet function can be measured using lumi-aggregometry or the PFA-100.
- Flow cytometry is a good complement to investigate receptor levels
treatments
Aspirin
* Warfarin
* Heparin
* Purinergic receptor inhibitors
Aspirin (acetylsalicylic acid)
Heparin
Purinergic receptor inhibitors
Warfarin
