6 - Clotting disorders Flashcards
What is the extrinsic pathway?
Exposer to tissue factor
F VII –> VIIa
=> activation of the common pathway
What is the intrinsic pathway?
Platelets activate FXII
cascade activates XI, IX IXa and VIIIa
activates common pathway
How does warfarin work?
Inhibits Vit. K reductase
inhibits protein C and S - inhibits clotting factors and enhances fibrinolysis decreases PT
What is the common pathway?
FX become acite and with co FV helps activate FII (to thrombin), which in turn activates fibrin.
How does Heparin?
inhibits FII and increase antithrombin activation.
What effects PT?
Warfarin
Factor II
Factor V
Factor VI
Factor X
Measures the extrinsic and common pathway
What effects APTT?
Heparin
Factor VIII
Factor IX
Factor XI
Factor XII (but no bleeding diathesis)
von Willebrand’s Disease
Measures the intrinxic and common pathway
If APTT and PT are prolonged consider:
Vit K deficiency
disseminated intravascular coagulation
rarely vWF deficiency
What are the VIt. K dependent factors?
Factor II
Factor VII
Factor IX
Factor X
Protein C
Protein S
What is the 50/50 mixture test?
APTT and PT done compared to with 50% normal bloodcontent
same times = factor deficiency
still prolonged times = factor inhibition
What is heamophillia A?
X linked disorder
deficiency of F VIII
What is haemophilia B?
X linked disorder
deficiency of FIX
What is Von Willibrand’s disease?
vWF deficiency which would have stabilised VIII and clotting
Reasons for Vit. K deficiency?
1) inadequate stores - malnutrition and haemorrhage disease
2) Vit. K malabsorption - Jaundice (fat soluble)
3) Oral anticoagulants
What is the treatment for haemophilia A?
IV FVIII concentrate
DDAVP
Tanexamic acid
What is the treatment for haemophilia B?
IV FIX concentrate
Which blood thinner can cause thrombocytopenia?
heparin
Treatment for VTE?
Anti-embolism stockings
LMWH and UFH
DOACs
Do not use Wafrin
What is Homan’s sign?
Tenderness with dorsiflexion of the ankle.
Indicates of DVT
Calf has a circumference >3cm compared to other.
What does this indicate?
DVT
What is Virchows triad?
1) Damaged endothelium
2) Blood stasis
3) Hypercoagulopathy
What does Tranexamic acid do?
Anti-fibrinolytic
What can Dessmopressin treat?
Haemophilia A and vW disease
How is LWMH different?
Longer half life greater bio availability Greater activity against Xa than IIa
What to ask in a history of bleeding?
bruising
epistaxis greater than 30 mins
GI tract bleeding
menses
heamaturia
bleeding at dentist, surgery family history
How to investigate a clotting disorder?
Thrombocytonpenia?
50/50 mixture test?
consider vWF deficeincy?
Management of PE
Start treatment unless investigations within 1 hour
Initially start LMWH before investigations
Later add warfarin or replace with DOAC
Investigaiton include: CTPA or V/Q scan
Diagnosis of PE
Wells score > 4
Wells score >4 and + D-dimer
Can confirm with CTPA
Symptoms of PE
Syncope
Tachycardia
Hypotension
Heamoptysis
Dyspnoea
pleuritic chest pain
What can mangement for recurrent PE/ DVT and not able to anti-coagulate sufficeintly?
IVC filter
Risk factors for PE
Stasis
recent surgery
pregnancy
oral contraceptive
previous VTE
FH
malignancy or chemotherapy
Diagnosis of DVT
Wells score >/= 2 and positive USS
Wells score = 1 and posotive D dimer
Management of DVT
Start LMWH if unless <4 hours until investigaiton
Add warfarin or replace with DOAC
What is an advantage of LMWH?
Quick onset
Easily stopped with protamine
How is anticoagulation via warfarin reversed?
PCC - prothrombine complex concentrate
Contains F II, V, VII, IX and X
takes 30 mins
Used instead of FFP - fresh frosen plasma
Vit. K takes 4-6 hours to work
PT is prolonged and the patient is not on warfarin. What is the most likley cause?
FVII deficiency
