Failure of secondary haemostasis Flashcards
What are the 2 main pathways of failure to secondary haemostasis?
- Multiple clotting factor deficiency
- Single clotting factor deficiency
What are some causes of multiple clotting factor deficiency?
- Disseminated intravascular coagulation
- Liver failure
- Vitamin K deficiency
- Warfarin therapy
How can liver failure lead to multiple clotting factor deficiency?
The liver’s hepatocytes are responsible for production of all clotting factors, so failure will lead to loss of production
What is the main cause of single clotting factor deficiency?
- Haemophilia
What is disseminated intravascular coagulation (DIC)?
This is the excessive and inappropriate activation of the haemostatic system (Primary, secondary, fibrinolysis)
What are some causes of DIC?
- Sepsis
- Obstetric emergency
- Malignancy (E.g. prostate cancer)
- Hypovolaemic shock
How does DIC occur?
- Systemic activation of coagulation due to release of procoagulant material (e.g. TF) or via cytokine pathways
- This leads to systemic fibrin generation and deposition, causing thrombosis and organ failure
- This causes consumption of platelets and coagulation factors and activation of fibrinolysis, further causing deficiency
- This means there is a mix of initial thrombosis, followed by a bleeding tendency de to consumption of clotting factors and dysregulated fibrinolysis
What are some complications of DIC?
Microvascular thrombosis formation
Clotting factor consumption
What is the main complication of microvascular thrombus formation?
End organ damage
What are some symptoms of clotting factor consumption?
- Bruising
- Purpura
- Generalised bleeding
What are some tests used in DIC?
- PT, APTT and TT
- FDP testing (D-Dimer)
- FBC
- Blood film
How will PT, APTT and TT be affected in DIC?
They are usually very prolonged, with a markedly reduced fibrinogen level
What will FDP testing show in DIC?
High levels of FDPs, including, D-dimer
Why are D-dimers raised in DIC?
Increased fibrin clot formation leads to intense fibrinolytic activity, causing the breakdown of fibrin into FDPs
What will FBC show in DIC?
Severe thrombocytopenia
What may blood film show in DIC?
Fragmented red blood cells
How is DIC managed?
Management involves treating the underlying cause and then replacement therapy
What does replacement therapy involve in DIC?
- Platelet transfusions
- Plasma transfusions
- Fibrinogen replacement
What is the function of vitamin K on clotting factors?
Vitamin K is responsible for the final carboxylation of clotting factors II, VII, IX and X (1972), giving them the required negative charge to bind to platelets and form the fibrin clot
How is vitamin K taken into the body?
Vitamin K is taken in through diet and absorbed in the upper intestine which requires bile salts for absorption
What are some causes of vitamin K deficiency?
- Poor dietary intake
- Malabsorption
- Obstructive jaundice
- Vitamin K antagonists (Warfarin)
- Haemorragic disease of the newborn (babies given vitamin K injection in birth to prevent this)
How will vitamin K deficiency affect PT and APTT?
This will caused prolonged prothrombin time and activated partial thromboplastin time (PT tests for tissue factor and factor 7 pathway, while APTT will test for the factor 8 and 9 pathway
What is haemophilia?
This is an X-linked, hereditary disorder in which there is a deficiency in a single clotting factor
What are the main types of haemophilia?
- Haemophilia A - Factor 8 deficiency
- Haemophilia B - Factor 9 deficiency
- Haemophilia C - Factor 11 deficiency
