Bleeding - Acquired Flashcards
What type of bleeding is ‘Disseminated Intravascular Coagulation’? (DIC)
Induced (acquired)
What is disseminated intravascular coagulation?
Intravascular activation of coagulation with a loss of localisation
What is the cause of DIC?
Coagulation cascade (especially thrombin) is activated wrongly
What is the effect on coagulation factors as a result of DIC?
Coagulation factors are consumed at a rate in excess of the capability of the liver to synthesise them
What is the effect on platelets as a result of DIC?
Platelets are consumed in excess of the capacity of the bone marrow megakaryocytes to produce them
Where are coagulation factors synthesised?
Liver
Where are platelets produced?
By megakaryocytes in the bone marrow
How does infection lead to coagulation problems?
Infection leads to sepsis which gives rise to tissue factor expression, a major driver of coagulation through the extrinsic pathway
What does infection cause the WBCs to release?
Cytokines
What are cytokines?
Proinflammatory mediators - chemical messengers telling the rest of the body about the infection. They tell cells to start expressing tissues factor (with no vascular injury)
Sepsis is a systemic infection. What does systemic mean?
Not localised - get tissue factor expression all over the body
What does tissue factor expression all over the body cause?
- Systemic coagulation activation leads to microvascular clots
- Consumption of clotting factors and platelets due to the infection being widespread and systemic
- Leads to bleeding (as coagulation factors used up) and then multiple organ failure and bruising
What are microvascular clots?
Blockage of small blood vessels
What type of bleeding is Abdominal Aortic Aneurysm (AAA)?
Induced (acquired)
What is AAA?
Progressive dilation of the abdominal aorta inferior to the renal and above the iliac arteries
What is the danger of AAA?
Aneurysm highly likely to rupture if gets too big, leading to major internal bleeding
What are chances of mortality during AAA rupture?
50%
Which factors have a requirement for Vitamin K?
F7, F9, F10, protein C and protein S
How does vitamin K work?
It is a cofactor for an enzyme, this enzyme takes glutamic acid and adds it to these factors (Glu –> Gla)
What happens without Vitamin K?
These factors are ineffective as cannot be bound to platelet surface during coagulation response. Can lead to bleeding
How do we get Vitamin K?
Not synthesised, only taken in by diet
What is a vitamin K antagonist?
Warfarin
What are anticoagulants?
Antibodies that neutralise clotting factor activity
What are lupus anticoagulants? What is their purpose?
Antibodies to phospholipid binding sites on clotting factors.
Prevent factors from accumulating on phospholipid surface.
