Prolonged bleeding Flashcards
What are congenital causes of prolonged bleeding?
Haemophilia A and B
Von Willebrand’s Disease
How does renal failure impact bleeding?
Impairs platelet function
What are acquired causes of prolonged bleeding?
- Therapeutic use of:
Anticoagulants
Antiplatelets - Renal failure
- Hepatic failure
- Bone marrow failure
What is purpose of haemostasis?
Prevent blood loss
When does haemostasis start?
When BV damaged / severed / ruptured
What are the mechanisms of haemostasis?
Vascular spasm
Platelet activation
Platelet aggregation
Activation of factor X and prothrombin
Fibrin mesh
Blood coagulation
How does hepatic failure impact bleeding?
Liver = source of clotting factors
Can impair absorption of vit K to synthesise factors 2, 7, 9, 10
How does bone marrow failure impact bleeding?
Reduce production of functional platelets
What can lead to bone marrow failure?
Leukaemia
Therapeutic drugs
Renal failure
Alcohol abuse
How does Warfarin work?
Interferes with vit K metabolism
Preventing synthesis of factors 2,7, 9, 10
Affects both intrinsic and extrinsic pathways
Importance of factor X?
Gets converted to factor Xa which converts prothrombin to thrombin which converts fibrinogen to fibrin which forms the clot
How do DOACs work?
Affects factor X conversion into factor Xa
What type of drug is Warfarin?
Vitamin K antagonist
Type of anticoagulant
Examples of DOACs?
Apixaban
Rivaroxaban
Edoxaban
Dabigatran
Disadvantages of warfarin over DOACs?
- Affected by foods
- Takes a long time to work
- Long time for effects to wear off after meds stopped
- Affects both intrinsic and extrinsic pathways, not specific, less predictable
Which foods can interact with Warfarin?
Green tea
Liver
Broccoli
Sprouts
Grapefruit
Alcohol
Pomegranate / cranberry juice
Items rich in Vitamin K
Which drugs interact with Warfarin and increase INR?
Miconazole
Fluconazole
Metronidazole
Erythromycin
All increase risk of haemorrhage
What prevents activation of platelets and clotting factors in BV normally?
Endothelial cells lining BV wall
What happens when BV wall damaged?
Lining of endothelial cells gone
Collagen fibres exposed
Foreign material introduced into BV
Platelets activated
Intrinsic and extrinsic mechanisms activated
How is blood clotting balanced?
Thrombin simultaneously catalyses plasminogen conversion to plasmin
Plasmin breaks down fibrin clots
Process fibrinolysis
Warfarin pt needs XLA what to do?
Never stop medx
Evidence base says stopping Warfarin cause more problems and SDCEP guidance
Check INR yellow book
If stable get INR within 72 hours of XLA
If unstable get INR within 24 hours of XLA
INR 4 or below
Proceed with XLA
Local haemostatic measures
What is most prolonged bleeding caused by in practice?
Iatrogenic
AKA Prescribed medx
E.g. oral antiplatelets, anticoagulants
Examples of oral anti platelets
Aspirin
Clopidogrel
Dipyramidole
Ticlopidine
How do anti platelets work?
Aspirin irreversibly binds to platelets, prevents aggregation
Clopidogrel irreversibly binds to receptors, prevents aggregation
Ibuprofen reversibly binds to platelets
How often are platelets renewed?
10 days
Which pts likely to take aspirin / clopidogrel?
Stroke
Vascular disease
Ischaemic heart disease
Thromboembolic disease
How to manage aspirin pt?
Do not stop aspirin
Takes 10 days for platelets to renew
Weeks for effects to be reversed
Risk of stopping greater than risk of continuing
Use local haemostatic measures
What is thrombocytopenia?
Reduced platelet count
What is normal platelet count?
150 000 - 450 000 / microlitre
What can cause thrombocytopenia?
Leukaemia
Anaemia
Pregnancy
Chronic alcohol abuse
Medx
Hereditary
How to manage pt with thrombocytopenia?
Safe to treat platelet count < 80 000
Get advice haematologist
May require steroids / platelet transfusion
Bruise very easily = ecchymosis
What types of pt on Warfarin?
Atrial fibrillation
Recurrent DVT or prev pulmonary embolism
Prosthetic heart valve
How is haemostasis measured?
Prothrombin time
What does prothrombin time reflect?
Activity of factor 7 in clotting cascade
How is PT used?
Calculate INR
What is INR?
International Normalised Ratio
= PT of pt / Mean PT of healthy group
What is INR in health compared to therapeutic warfarin range?
Health = 1
Warfarin = 2 - 4
What should anticoagulation record contain?
Yellow book
Reason for anticoagulation
Target INR
Contact details of clinic
Warfarin dosages
Recent INR records - stable or unstable?
What is half life of Warfarin? What does this mean?
48 hours
Takes 2 days for changes in dose to affect INR
Management of Warfarin pt using anti fungal for angular chelitis?
Antifungals = metronidazole / fluconazole / miconazole
Antifungals contraindicated for Warfarin pts as increase INR
Do not stop Warfarin
Prescribe another anti fungal agent
Risks associated with increased INR <4?
- Increase risk of haemorrhage
- Retinal haemorrhage = visual loss
- Haemoarthrosis = loss knee function
- Subdural haematoma = death
Which drugs interact with Warfarin to decrease INR?
Carbamazepine
Increases risk of thrombosis
What drug can reduce prolonged bleeding?
Tranexamic acid
How does tranexamic acid work and when used?
Stops plasminogen being converted to plasmin
So no fibrinolysis
Stops clots being digested
Not commonly used
Mouthwash
Why do not prescribe aspirin to children U16
Reyes syndrome
Which aspect of haemostasis do antiplatelets affect?
Platelet aggregation
Which aspect of haemostasis does Warfarin affect?
Clotting cascade
Factors 2, 7, 9, 10
Virchow’s Triad?
- Damage to endothelial lining
- Hyper coagulable state
- Arterial / venous blood stasis
Predispose to thrombosis
