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What are the three stages in a vessel that arrest haemorrhage?
- 1. Contraction of vessel wall, vascular response
- 2. Platelet aggregation - unstable clot
- 3. Initiation of clotting cascade - stable fibrin clot
Haemorrhagic disease can be divided into 2 situations:
- 1. Where bleeding is profuse at the site of operation. Therefore PROLONGED bleeding, but clotting may be normal.
- 2. Where bleeding stops for a short time after op, but persistent haemorrhage occurs later owing to failure of the blood to clot. Therefore bleeding time may be normal, but there is an abnormality in coagulation.
Local causes of haemorrhage (3):
- Local vascular lesion (eg. haemangioma)
Why does trauma cause Haemorrhage?
Excessive trauma causes ST bleeding and may also damage blood vessels.
Why does infection cause Haemorrhage?
- Bacteria can break down the clot.
- Loose pieces of bone or retained tooth fragments also favour secondary infection.
Systemic causes of haemorrhage (3)?
- 1. Platelet disorders
- 2. Vessel disorders
- 3. Coagulation disorders
Generally what sort of symptoms would you see from platelet disorders
- Bruising of skin
- Bleeding from mucosal membranes
Generally what sort of symptoms would you see from coagulation disorders?
- Bleeding into joints (haemarthroses)
- Muscle haematomas
What platelet disorders exist?
- Decrease in platelet NUMBER
- Decrease in platelet FUNCTION
What can cause a decrease in platelet NUMBER (3)?
- -Thrombocytopenia (idiopathic, drugs, leukaemia, autoimmune)
- - hypersplenism
What is DIC?
Disseminated intravascular coagulation. Small clots throughout body consume platelets available for clotting.
What can cause a decrease in platelet function?
- Von Willebrands disease
Antiplatelet drugs aim to inhibit thrombus formation in which circulatory system?
- Arterial circulation, where anticoagulants have little effect.
- They may double bleeding time, but minimal affect on coag.
Why do people take low dose aspirin daily?
Patients with established cardiovascular or cerebrovascular disease
How do aspirin and clopidogrel work?
- Inhibit platelet aggregation to blood vessel wall.
- Irreversible, lasting for the life of the platelet.
- 7-10 days
How does dipyridamole work?
- Used as an adjunct to anticoag, or in pts with stroke and TIAs
- Reversible effect on enzyme in platelets and vessel cell walls.
What are the features of Von willebrands disease?
- Hereditary disease. VWF helps attract platelets, and binds with factor 8 to prevent its clearance away from site.
- Decrease level of von Willebrand factor +/- factor 8
- DDAVP can be given to raise the level of VWF, but does not work in all types of the disease.
- Factor 8 is also given in haemorrhage cases.
Give an example of a vessel disorder that can cause increased bleeding?
- Hereditary hemorrhagic telangiectasia
- Inherited condition
- Abnormal blood vessels which are delicate, prone to bleeding.
Coagulation disorders can be inherited or acquired, give examples:
- Inherited: Haemophilia A, B, VW disease
- Acquired: Liver disease, biliary disease, DIC, drugs - warfarin
Haemophilia A is deficiency in which factor?
Haemophilia A, classify mild, moderate and severe?
- Mild - 5-40% (DDAVP will do in these cases)
- Moderate - 2-5%
- Severe - 0-1%
What is DDAVP?
- Desmopressin, a synthetic substance with an action similar to vasopressin.
- Increases renal water absorption, and at high concs increases level of factor 8 and VWF.
- Subcutaneously or intranasal spray.
Dental relevance of Haemophilia A?
- No regional blocks, or injections in FOM or IM. Factor 8 cover must be given.
- AB cover can protect clot from breaking down.
Haemophilia B defiency in which factor?
9. Factor 9 has a longer half life, so can be given daily.
Tranexamic acid - what type of drug is it?
An antifibrinolytic drug. Available as a mouth wash.
Liver disease will result in:
- Vit K deficiency
- Reduced synthesis of clotting factors
- Funtional abnormalities of platelets
Pt with liver disease may need in an emergency:
Investigations to do when assessing potential bleeding problems:
- FBC - Platelet count
- Blood film - Morphology of cells
- Coagulation screen - aPPT and PT measures if clotting factors are working properly.
Prothrombin time (PT) is prolonged in which situations?
- Abnormalities of factors 7, 10, 5, 2, 1
- Liver disease
- Pts on Warfarin
Haemophilia A investigation will show:
- Decreased factor 8
- PT normal
- aPTT prolonged
In which side of the circulation to anticoagulants work best to prevent thrombus formation?
Venous. Slow-moving, thrombus is made from a Fibrin web emeshed with platelets and RBCs.
Warfarin inhibits Vit K synthesis. What factors are dependent on Vit k?
- 2, 7, 9, 10
- Therefore treatment with Vit K, Fresh frozen plasma
Why do patients take warfarin SHORT term?
- Prophylaxis/prevent DVT
- Recent MI 3/12
- Established DVT 3/12
- PE 3-6/12
- Xenograft cardiac valves 3/12
Why do patients take warfarin LONG term?
- Recurrent venous thromboembolism
- Rheumatic heart disease
- Atrial Fibrillation
- Prosthetic heart valves
What drugs does Warfarin interact with by potentiating it?
- Fluconazole, itraconazole, miconazole -- very serious!!
- NSAIDs (caution increased GI bleeds)
What drugs decrease the function of Warfarin?
- Erythromycin? - unpredictable.
What is the INR
- Ratio of patient's PT to a normal reference
- Normal - 1
INR requirements for dental procedures:
- Below 4.0 for atraumatic removal of upto 3 teeth. Suture and pack.
- MOS and multiple extractions below 3.0