Session 5 Flashcards
What are the 3 major steps to hemostasis?
- Vasoconstriction
- Temporary blockage of a break by a platelet plug
- Blood coagulation, or formation of a fibrin clot which stabilises the friable platelet plug into a stable clot.
What is thrombosis?
The formatiom of a solid mass from the constituents of the blood, within the circulatory system, during life.
NOT THE SAME AS CLOTTING!
What is Virchow’s triad?
They are three fudnamental predisposing factors to thrombosis.
- Abnormalities of the flow of blood
- Abnormality of the blood vessel wall
- Abnormalities of the constituents of the blood
What is embolism?
Embolism is the blockage of a vessel by solid, liquid or gas at a site distant from its origin.
Over 90% of emboli are thrombo-emboli.
Which materials can embolise apart from a thrombus? (5)
- Air
- Amniotic fluid
- nitrogen
- medical equipment
- tumour cells
Which clotting factors are involved in the Extrinsic pathway?
7
Which factors are involved in the intrinsic pathway?
8,9,11,12
Which pathway does PT test?
extrinsic
Which pathway is measured by aPTT?
Intrinsic
What does PT stand for?
Prothrombin time
What is “bleeding time”?
How long it takes after injury for bleeding to stop. It is a measure of platelets.
Which tests will evaluate platelets?
Bleeding time
Do a normal PT and aPTT indicate that there is no clotting abnormality?
no! even if PT and aPTT are nirmal, bleeding time could still be altered as PT and aPTT don’t test platelets.
What ar the main clinical features of Haemophilia A?
- Sebere haemorrhage after sirgarey or trauma
- Spontaneous bleeding especially in joints = haemarthrosis
- NO petechiae normally
Haemophilia A is a deficiency in which factor?
8
What is the pattern of inheritance of haemophilia?
X-linked recessive
What is Christmas disease?
It is haemophilia B, ie. Factor 9 deficiency.
How is haemophilia B inherited?
X-linked recessive
Are haemophilia A and B straightforward to differentiate clinically?
No. Nor with very basic tward-based tests. But laboratory tests will easily tell them apart.
Is bleeding time normal or abnormal in a factor 7 deficient patient?
normal! platelets arent affected it’s the PT that is affected
Which test does heparin prolong?
aptt
What is von Eillebrand disease?
It is a deficiency or abnormality in Von Willebrand factor.
This protein has 2 functions:
1. Assists platelet plug formation by attracting circulating platelets to site of damage.
2. Stabilises factor VIII, protecting it from premature destruction
What is the common bleeding pattern in vWd disease?
mucosal bleeding reflecting the inadequate platelet function and adhesion. But patients can vary from being asymptomatic to having severe bleesing disorders.
In vWd which tests are abnormal?
PT normal
aPTT prolonged as VIII no longer optimally protected
Bleeding time prolonged as platelets not optimally recruited to damage site.
