Haemostasis + Haemorrhagic Disorders Flashcards
1. Knowledge of disorders associated with haemostasis 2. Categorise bleeding disorders 3. Knowledge of signs and symptoms of bleeding disorders 4. Knowledge of oral anticoagulants 5. Knowledge of dental relevance of common bleeding disorders 6. Interpret basic haematological data
Define haemostasis
The process causing bleeding to stop and so keeping blood in the damaged vessel
How does haemostasis occur
Primary haemostasis = platelet clot formation
Secondary haemostasis = coagulation strengthening clot
Describe primary haemostasis
- Vasoconstriction occurs due to nerve reflex and endothelin release from vascular endothelium
- Reduces blood flow
- Platelet plug forms via adhesion of platelets via vWF
Describe secondary haemostasis
Coagulation occurs to strengthen clot through formation of a fibrin meshwork
- all clotting factors made in liver apart from VIII
- factors are activated upon injury
- collagen exposure causes intrinsic pathway
- tissue factor causes extrinsic pathway
- join to form common pathway to give fibrin
Which clotting factors are produced by endothelial cells
VIII and vWF
Which clotting factors are vitamin K dependant
II, VII, IX, X
List the primary haemostasis bleeding disorders
- Vascular disorders
- Von Willebrand disease
- Palatal disorders
List the secondary haemostasis coagulation disorders
- Clotting factor disorders
List congenital haemostasis disorders
- Von Willebrand disease
- Haemophilia A
- Haemophilia B
List acquired haemostasis disorders
- Thromboytopenia
- Platelet dysfunction due to drugs
- Antiplatelet therapy
- Anticoagulant therapy
Name a vascular disorder
Hereditary haemorrhagic telangiectasia (Osler-Rendu-Weber syndrome)
What are the causes of vascular disorders
- Autosomal dominant
- Associated with IgA and vWF deficiency
Describe the clinical presentation of vascular disorders
- Telangiectasia (spidery veins) on skin and mucosa
- Rarely causes bleeding
- Adolescent diagnosis due to epistaxis (nose bleeds)
- Can result in iron deficiency and anaemia due to intestinal bleeding
How can vascular disorders be tested for
CT
MRI
Angiography
Capillary microscopy
How can vascular disorders be treated
- Cyrosurgery
- Argon laser treatment if telangiectasis bleed
What are the dental relevances of vascular disorders
Bleeding from oral surgery is troublesome
Regional LA should be avoided and infiltration is better
What are the causes of Von Willebrand Disease
- vWF deficiency which is inherited (not sex linked)
- this mediates platelet adhesion to damaged endothelium and so prevents aggregation in absence
- stabalises and transports factor VIII
Describe the clinical presentation of Von Willebrand Disease
- bruising and epistaxis
- prolonged bleeding in oral surgery
- GI bleeding and menorrhagia (XS menstrual bleeding)
How is Von Willebrand Disease tested for
Lab results show decreased vWF and VIII and lower aggregation, shows prolonged activated partial thromboplastin time
How is mild Von Willebrand Disease treated
Desmopressin which increases vWF and VIII production
How is severe Von Willebrand Disease treated
vWF replacement through rich plasma and through antifibrinolytic drugs which decrease the breakdown of clots
What is the dental relevance of Von Willebrand Disease
- prolonged bleeding and oozing post-extraction
- avoid regional LA
- avoid aspirin and NSAIDs
What is a safer alternative for aspirin and NSAIDs for patients with blood clotting disorders
Acetaminophen
Co-codamol
What causes platelet deficiency
- Hereditary; Bernard-Soulier syndrome = rare (platelets are enlarged and don’t have platelet membrane so cannot adhere)
- Megakaryocyte suppression
- Vitamin B12 and folate deficiency
- Bone marrow failure
- Thrombocytopenia
- Splenomegaly (platelet sequestration)
What is the dental relevance of platelet deficiency
A platelet count of thrombocytopenic patients should be taken before treatment - PC < 20,000/mm3 increases the risk of spontaneous bleeding
What causes platelet dysfunction
- Antiplatelet drugs; aspirin, NSAIDs, clopidogrel, dipyridamole
- all but NSAIDs are irreversible on platelet lifespan
- NSAIDs are reversible because the drug clears after 24-48 hours
For minor procedures the drug should be continued and local haemorragic agents should be given post operatively
What is the clinical presentation of platelet dysfunction
Easily bruising and bleeding
- petechiae
- purpura
- ecchymosis
What causes haemophilia
X-linked disorders; VIII and IX deficiency
What is the clinical presentation of haemophilia
- Mild = minimal bleeding
- Moderate = bleed after minor surgery needs attention
- Severe = bleeds without provocation
Haemorrhage stops immediately after injury but there is intractable oozing which causes bleeding into deep tissues
Need to monitor signs of haematoma an give prophylactic VIII replacement
Outline treatments for haemophilia
Desmopressin (increase FVIII production)
Replacement therapy
Antifibrinolytic agents = trxnexamic acid, EACA
What are the common indications of anticoagulant therapy
Atrial fibrillation, cardiac valvular disease, mechanical prosthetic valves, ischaemic heart disease, DVT, pulmonary embolism, renal dialysis, TIAs of strokes
What are the actions of warfarin and how are they monitored
Inhibits vitamin K dependant factors
Monitored via INR/PT (INR is better because it is standardised)
What is the relationship between INR and bleeding risk
Increased causes greater risk
INR > 4 the patient should be referred to hospital for dental care
What are the actions of heparin and give examples of the different types of heparin
Inhibits factors II and X
- it is a short lived anticoagulant monitored via APTT
Standard heparin (IV) = immediate management of acute thromboembolic events
LMWH (subcutaneous) - non-hospitalised ambulatory patents post discharge
Why are NOACS useful
Non-vitamin K oral anticoagulants
- more predictable levels of anticoagulation
- don’t require regular monitoring
- wider therapeutic range and easier management
- more effective and safer
Give examples of NOACS and their actions
- Dabigtran = inhibits IIa
- Apixaban = inhibits Xa
- Rivaroxaban = inhibits Xa
- Edoxaban = inhibits Xa
Dental relevance of haemophilia
- Minimise surgical intervention (preventative dentistry)
- Risk of haemorrhage after surgery/LA so don’t use regional block
- Ensure adequate levels of clotting factors (VIII/IX)
- Monitor for signs of haematoma formation
- For head+neck trauma give prophylactic factor VIII replacement
Dental relevance of warfarin
Measure INR within 24 hours of surgery (INR>4 then refer to hospital for dental care) and be aware of drug interactions
Increased INR means increased bleeding risk
Bleeding risk is minimised by avoiding concurrent use of medications by giving alternative antifungals = Nystatin and using paracetamol/co-codamol
What are the potential drug interactions of warfarin
- Warfarin + metronidazole (given for dental infections)
- Warfarin + macrolides (erythromycin)
- Warfarin + azole antifungals (miconazole)
- Warfarin + aspirin/NSAIDs (enhance warfarin effects)
What are the indications for NOACS
Stroke prevention in AF patients Thromboembolic disease (DVT, PE)
How do non-vitamin K oral anticoagulants work and what are the dental recommendations for their use
They have a rapid onset and short half-lives and modify the patients’ coagulation
For those at low risk their dental treatment should be carried out without treatment interruption
For higher bleeding risk patients, advise them to miss (apixaban/dabigatran) or delay (rivaroxaban) on the day of dental treatment for surgical procedures
