prolonged bleeding Flashcards
What is haemostasis
The control of bleeding in health
What is prolonged bleeding defined as in the contact of dentistry
Bleeding which:
- Continues beyond 12 hours
- Causes the patient to call or return to the dental practitioner or A&E
- Results in the development of a large haematoma or ecchymosis within the oral soft tissues
- Requires a blood transfusion
How do we classify the aetiology of disordered haemostasis
- Congenital cause
2. Acquired cause
Which classification of aetiology of disordered bleeding is more commonly seen in dentistry
Acquired disorders
What can the abnormality responsible for disordered haemostasis be
- Quantitive (amount)
2. Qualitative (abnormality)
What can be affected in quantitative abnormalities of bleeding
- Reduced amounts of factor VIII (haemophilia A)
2. Reduced number fo platelets (thrombocytopenia)
What can be affected in Qualitative abnormalities of bleeding
Platelets with abnormal function
What is haemophilia A
Reduced amounts of factor VIII
What can congenital causes of prolonged bleeding be due to
Abnormalities of
- Soluble Coagulation Factors:
- Platelets
- Blood vessels
Give examples of disorders that can result in abnormalities of soluble coagulation factors
- Haemophilia A
- Haemophilia B
- Von Willebrand’s disease
Name the condition that results in congenital reduction in factor VIII
Haemophilia A
What Is haemophilia B
congenital reduction in factor IX
What is von Willebrand’s disease
Congenital reduction on von Willebrand’s factor
Give an example of a disorder that can result in abnormalities of blood vessels
Hereditary Haemorrhagic Telangiectasia
What can acquired causes of prolonged bleeding be due to
- Iatrogenic
- Renal failure
- Hepatic failure
- Boen marrow failure
Name the most common cause of prolonged bleeding in the UK
Iatrogenic
What can result in iatrogenic prolonged bleeding
Anti-platelet drugs and warfarin
What is renal failure associated with
impaired platelet function and prolonged bleeding.
Name the 2 mechanism which can contribute to disordered haemostasis in liver function
- Reduced synthesis of soluble clotting factors and hepatic failure
- Obstructive jaundice
What can happen in obstructive jaundice
Absorption of vitamin K is impaired
Why is vitamin K important
Needed for the synthesis of clotting factors II, VII, IX, X
Where are platelets formed
In the bone marrow
What can bone marrow failure result in
Reduced production of functional platelets
Other than platelets what else is formed in the bone marrow
Erythrocytes
What are erythrocytes
Red blood cells
What can bone marrow failure be caused by
- Leukaemia
- Therapeutic drugs
- Renal failure
- Alcohol abuse
How can we measure disordered haemostasis
- Prothrombin time
- International normalised ratio
- Activated partial Thromboplastin time
- Bleeding time
How do we measure prothrombin time
By taking a venous damper of blood
What is the value of the prothrombin time determined by
The activity of clotting factor VII
How is the international normalised ratio calculated
(prothrombin time of patient)/ (mean thrombin time of healthy patient)
What is the INR number in health
1.0
What does a high iNR number mean
Greater:
- Degree of anticoagulation
- Risk of adverse side effects
What is a therapeutic INR typically between
2.0-4.0
Why do we calculate the activated partial thromboplastin time
For the assessment of heparin anticoagulation
What is bleeding time a measurement of
Platelet function
What are the consequences of prolonged bleeding
- Acute haemorrhage
2. Chronic haemorrhage
What is chronic haemorrhage a MAJOR cause of in the UK
Anaemia
How can we manage patients suffering with prolonged bleeding
A good HISTORY
What do we want to fund out when taking a history
Identification of known and unknown problems
How is haemostasis usual achieved
- Vascular spasms
- Platelets plug formation
- Blood coagulation
- Growth of fibrous tissue in the Hole in the vessel
What is platelet plug formation activated by
Tissue damage which exposes sub endothelial collagen
How is the Platelet plug formed
- Platelets activated as a result of tissue damage
- Enhanced Platelet adhesion and aggregation
- Enhanced activation of factor X
When are antiplatelet drugs prescribed
Fore Treatment or prevention of further cardiovascular disease
Give examples of Antiplatelet Drugs
- Aspirin
2. clopidogrel
How does aspirin work
It binds irreversibly to platelets
It inactivated the COX-1 enzyme
what is the importance of the COX-1 enzyme
is needed for thromboxane A2 mediated aggregation
How does clopidogrel work
by binding to the P2Y12 receptor irreversibly and preventing Adenosine Di Phosphate (ADP) mediated aggregation
When are platelets renewed
Every 10 days
Over which age is aspirin prescribed
Over the age of 16
Why is aspirin not given to children under 16 years
because of the risk of Reye’s Syndrome
what is reyes síndrome
(rare condition which can cause potentially fatal swelling of the liver and the brain
State the normal platelet level in venous blood
150,000 - 450,000/ml
when are platelets levels reduced
- leukaemias,
- some anaemias,
- pregnancy,
- chronic alcohol abuse,
- medication
- Idiopathic Thromobocytopenia
What is purpura
Teram used to describe a rash of tiny bruises
What is eechymosis
refers to larger bruises
A count of how many platelets is safe to carry on dental treatment
Over 80,000/ml
What are the indications for the prescription of warfarin
- Atrial fibrilaion
- Previous recurrent DVT or PE
- Heart valve replacement
What is warfarin
A vitamin K dependent clotting factor agonist
How does paraffin work
It works at the level of the activation fo the clotting cascade leading to diminished clot formation
What do patients on warfarin usually carry
A yellow book
What does the yellow book warfarin patients carry record
Carries records of their iNR
Give examples of drugs that can potentiate warfarin
MICONAZOLE
FLUCONAZOLE
METRONIDAZOLE
ERYTHROMYCIN
What do drugs that potentiate warfarin do
Increase risk of haemorrhage
Give examples of drugs that can reduce the effect warfarin
CARBAMAZEPINE
Name some herbal medicines and food stuff that can interfere with warfarin metabolism
- Ginseng
- St Johns Wort
- Green tea (rich in vit K)
- Liver
- Broccoli
- Brussel sprouts
- High oxalate greens like spinach,
- Alcohol
- coriander and cabbage
- Grapefruit
- Pomegranate juice
- Cranberry juice