Coagulation Disorders Flashcards
What are the different stages of haemostasis?
- constriction of blood vessels
- Temp platelet plug =primary haemostasis
- Activation og coagulation cascade
- Formation of ‘fibrin plug’ =secondary haemostasis
- Clot resolution - tertiary haemostasis.
What is the process of vasoconstriction in coagulation?
Within 30 minutes of trauma to bv
ECM/collagen exposed to blood components
Release of clotting factors and platelets
Altered substances released by endo cells - dec NO, increase endothelin and thromboxane
What happens during formation of a primary platelet plug?
Cytokines and inflammatory markers lead to adhesion of platelets and aggregation
vWF helps platelets adhere to site on injury
Activates platelets release granules - positive feedback for process
What is the role of the coagulation cascade in blood clots?
Extrinsic and intrisncie pathway
Occr spontaneous and result in activation of factor X.
Continues as the common pathway.
Each step involves various coagulation factors
End goal - fibrinogen-> fibrin to form a stable clot and mesh formation (secondary haemostasis)
What coagulation factors are Vitamin K dependent?
1972
10, 9, 7, 2
How does clot resolution occur?
Tertiary haemostasis - activated platelets contract, leading to shrinkage of the clot volume.
Plasminogen is activates to plasmin = lysis of the fibrin clot
Restores blood flow in the damaged vessels.
What are the different indications for a coagulation screen?
- Confirm a suspected coagulopathy
- Acute blood loss
- Monitor a patient on anti-coagulant drugs
- Assess coagulation status prior to surgery
- Assess the synthetic function of the liver
What investigations are commonly ordered alongside a coagulation screen?
FBC for platelets
LFTs for general liver function
Albumin - liver synthetic function/malnutrition
D-dimer (if clinically indicated)
Cross match and group and save - if requiring blood transfusion.
How should a prothrombin time (PT) be interpreted?
Extrinsic pathway
It can be standardised as the INR for monitoring warfarin
Mainly focuses on factor 7
Higher time indicates higher bleeding risk.
What can cause a deranged PT test result?
Overall clotting factor synthesis - liver disease, DIC, Vitamin K deficiency and warfarin.
How should an activated partial thromboplastin time (aPTT) be interpreted?
Intrinsic pathway
Normally focus on VIII, IX, XI
High time = increased risk of bleeding.
What can cause an abnormal aPTT?
Overall cloting factor synthesis/consumption - DIC, liver failure, VitK defieicny
Von Willebrands disease
Haemophilias
Note anti-phospholipid syndrome can cause a high aPTT despite being a clotting disorder as it inactivates phospholipid in test.
What is the genetics of Haemophilia?
X-linked recessive condition (primarily affects males)
Haemophilia A - factor 8 deficiency - more common
Haemophilia B - factor 9 deficiency - Christmas disease
How does Haemophilia tend to present?
Severe bleeding disorders with a risk of excessive bleeding in response to minor trauma or even spontaneously.
Neonates - IC haemorrhage, haematoma, cord bleeding
Spontaneous haemarthrosis (ankle, knee, elbow).
May bleed from oral mucosa, epistaxis, GIT, UT.
What is the common management of Haemophilia?
IV infusion of affected clotting factors.
(beware of formation of inhibitor antibodies against these)
What is the most common inherited bleeding disorder?
Von Willebrand’s disease
What is the genetics behind Von Willebrands disease?
Autosomal dominant
Deficient, absence of malfunctioning of vWF - reduces platelet adhesion, aggregation.
What are the three different types of von Willebrand disease?
type 1 - partial deficiency of vWF (most common
type 2 - reduced function of vWF
type 3 - complete deficiency of vWF (rare and severe)
What is the common presentation of von Willebrands disease?
Unusually easy, prolonged/heavy bleeding - gums, nosebleeds, menorrhagia, surgical operation sites
FH very important.
How is von Willebrands disease often diagnosed?
History - inc FH
Bleeding scores
Lab investigation - coag screen
Genetic testing
Common have a low F8 as vWF transports this.
What is the management for von Willebrands disease?
Only in response to significant bleeding/trauma:
1. Desmopressin (mimics ADH) - stimulates vWF release from endothelial cells
2. Tranexamic acid (anti-fibrinolytic)/mefenamic acid (NSAID)
3. vWF infusion +/- factor 8
4. Mirena coli, norehisterone, hysterctomy
What is disseminated intravascular coagulation?
Rare but lifethreatening - abnormal blood clotting throughout the body.
Two stages:
1. Overactive clotting -> blood clotes throughout vessels = organ damage
2. Platelets and clotting factors run out -> uncontrolled bleeding
What commonly causes DIC?
Inflammation - sepsis or malignancy
What is the common treatment for DIC?
Manage underlying cause +/- blood products.
