clotting Flashcards
what are the components of blood involved in clotting
coagulation factors and platelets
describe the coagulation process
which medications can affect clotting
what are the most common inherited blood disorders
describe the importance of clotting in dentistry
what are the stages to clotting
injury to a vessel
vascular phase, whereby the vessel attempts to stop the bleeding
platelet phase aka primary haemostats
coagulation phase aka secondary haemostats
clot formation and stabilisation
clot dissolution
describe the vascular phase of clotting
this is when the vessel attempts to stop the bleeding
the vessel will vasoconstriction, via smooth muscle action.
injury exposes the collagen in the blood vessel wall, and the fibres will kickstart the healing process.
there is release of factors from the endothelial cells lining the vessel, which includes
- adp platelets
- tissue factor
- endothelins
describe the platelet phase of clotting
this is when the exposed collagen, apd and endothelins attract platelets.
the platelets become sticky and adhere to each other, causing a platelet plug via aggregation.
how does the platelet plug form
the exposed collagen released ADP and endothelia’s which attracts the platelets.
there is platelet adhesion and aggregation, which leads to more adp and thromboxane a2 being released which attracts more platelets. this is positive feedback.
this plugs the vessel injury but is a temporary solution, as the weaker repair compared to the finished product
what is the aim of the coagulation phase
to create a more permanent, robust clot
what is the clot made from
fibrin
what is the coagulation cascade
a series of proteins ultimately leads to clot formation through two separate pathways; intrinsic and extrinsic
parallel to this is fibrinolysis which is clot breakdown to prevent spontaneous clotting in health
where does the intrinsic coagulation cascade occur
in the bloodstream
where does the extrinsic coagulation cascade occur
in the vessel wall
what are some medications that affect platelets
aspirin
clopidogrel
dipyridamole
ticagrelor
what are some medications that act as anti coagulants
warfarin
edoxaban
rivaroxaban
apixaban
dabigatran
why would someone be prescribed a blood thinner
coronary disease to prevent myocardial infarction or stroke
peripheral artery disease to reduce symptoms
prosthetic heart valves to prevent a clot
atrial fibrillation to prevent a stroke
pulmonary embolisms and deep vein thrombosis to treat or prevent the conditions
following surgery or pregnancy
what is coronary artery disease
narrowing of the vessels supplying blood to the heart
what is peripheral artery disease
narrowing of the vessels supplying the legs or the arms
what is atrial fibrillation
heart arrhythmia
how many mg aspirin a day
75mmg
how many mmg aspirin is given in acute myocardial infarction or in a stroke
300mmg
what is the mechanism of action of aspirin
inhibits the COX enzyme, reducing production of thromboxane A2, thereby reducing the platelet aggregation
interfering with the canalisation of the formation of thromboxane a2 prevents platelet aggregation, which is irreversible, and the platelets live for 7-10 days. should be familiar with this mechanism of action. the membrane f the platelet will begin to break down
do people need to stop taking aspirin for dental treatment
no
what is the lifespan of platelets
7-10 days
what is the common dose of aspirin
75 mmg
what is aspirin used for
preventing blood clots in vessels when they are narrowed due to atherosclerotic disease
what are some conditions requiring 75mmg aspirin a day
coronary artery disease, secondary prevention
transient ischaemic attack, secondary prevention
describe warfarin
this drug is used less nowadays but it inhibits the production of vitamin k which is essential in formation of coagulation factors 2, 7, 9 and 10.
used for prosthetic heart valve patients as they have a risk of clotting due to blood stagnation
what is the INR
international normalised ratio used to monitor warfarin
what are the indications with medications and food stuffs observed in warfarin
metronidazole
fluconazole
NSAIDs
alcohol
grapefruit
describe DOACs
these are direct oral anticoagulants including ecoxaban, rivaroxaban, apixaban, dabigatran
these are taken over from warfarin for conditions such as atrial fibrillation, PE and DVT
what is the mechanism of action of DOACs
inhibits factor Xa and inhibits free thrombin
does DOAC require monitoring
no
compare warfarin vs DOACs for onset
slow vs rapid
compare warfarin vs DOACs for dosing
variable vs fixed
compare warfarin vs DOACs for food effect
yes vs no
compare warfarin vs DOACs for drug interactions
many vs a few
compare warfarin vs DOACs for monitoring
yes vs no
compare warfarin vs DOACs for offset
long vs shorter
describe injectable anticoagulants
used after giving birth or during long hospital stays
or where patients are unable to take DOACs
what is the mechanism of action of injectable anticoagulants
inhibits the formation of factor Xa and thrombin
what are some injectable anticoagulants
dalteparin
enokaparin
what are the general principles for dentistry and anti coagulant medications
delay dental treatment until the anticoagulant plan finishes
plan treatment for early in the week and in the day
atraumatic surgery
consider packing and suturing
ensure bleeding has stopped
advise paracetamol for pain relief
what are bleeding disorders
these are disorders where there is impairment of the different elements of clotting, like the platelets, clotting factors or in liver disease
what are some acquired bleeding disorders
liver disease
thrombocytopenia
what are some inherited bleeding disorders
von willebrand disease
haemophilia A
haemophilia B
describe liver disease in relation to bleeding disorders
can result in a bleeding tendency due to reduced platelet numbers and function
the thrombopoeitin hormone stimulates platelet production and is produced in the liver
there is also impaired production of coagulation factors
describe thrombocytopenia
this is when there are low platelet numbers due to reduced production or increased destruction
how does reduced platelet production occur
b12 deficiency
folic acid deficiency
liver disease
leukemia
chemotherapy
how does increased destruction of platelets occur
immune drive, top or heparin induced thrombocytopenia
describe von willebrand disease
this is the most common inherited cause of abnormal and prolonged bleeding
an autosomal dominant inheritance, causing an absent or defective von willebrand factor
this leads to impaired platelet aggregation and impaired transport of factor 8 to the wound
what is type 1 von willebrand
this involves partial deficiency of von willebrand factor, the most common and mildest type
what is type 2 von willebrand
this involves reduced function of von willebrand disease
what is type 3 von willebrand disease
this involves a complete deficiency of von willebrand factor and is the most rare and severe type
what is the inheritance type of each von willebrand disorder
type 1 is autosomal dominant
type 2 is autosomal dominant
type 3 is autosomal recessive
describe von willebeand disease in dentistry
does not require daily treatment, but for dental treatment likely to cause bleeding, should cover with:
- tranexamic acid mouthwash if disease is mild and the procedure is low risk
- DDAVP/desmopressin if more likely to cause bleeding
- von willebrand factor concentrate if severe disease and high risk procedure
how does DDAVP and desmopressin work
increases von willebrand factor production and factor 8 production
describe the inheritance pattern of haemophilia
x linked recessive, primarily affecting males
describe haemophilia A
this affects deficiency factor 8
describe haemophilia B
this affects deficiency of factor 9
what does haemophilia present as
spontaneous bleeding into joints and significant bleeding following minor trauma
how is haemophilia A treated
DDAVP/desmopressin or factor 8 concentrate if more severe
how is haemophilia B treated
factor 9 concentrate, as DDAVP is not effective
how long before dental treatment should blood products be given to haemophiliac patients
30 minutes
factor percentage of severe haemophilia
less than 1%
factor percentage of moderate haaemophilia
2-5%
factor percentage of mild haemophilia
6-40%
describe dental treatment for severe haemophilia
enhanced preventative advice and treatment
all treatment except for prosthetics carried out in hospital setting
describe dental treatment for moderate haemophilia
enhanced preventative advice and treatment
manage as for severe haemophilia
describe dental treatment for mild haemophilia
enhanced preventative advice and treatment
not all treatments in hospital , seen every two years in specialist dental team at haemophilia centre
what to note when administering local anaesthetic to bleeding disordered patients
avoid the inferior alveolar nerve block as there is risk of bleeding from the. muscle. can lead to haematoma or airway compromising
what administration for local anaesthetic is preferred for patients with bleeding disorders
buccal infiltration
intra papillary injections
intra ligamentary injections
what are the four blood tests related to clotting
full blood count
liver function est
inr
coagulation screen
what is the full blood count
counting red cell, white cell and platelet
what is the liver function test
this shows the acute liver damage
most coagulation factors are made in the liver
less helpful about specific synthetic function
what is the INR
the international normalised ratio used to compare how long it takes patients blood clotc compared to laboratory standard
the higher the number, the longer it takes to clot
usual range for patients on warfarin is 2-4
healthy person on no medication is 1
normally should be less than 4 for medical treatment
what is coagulation on screen
this looks at intrinsic and extrinsic pathways and gives good insight into livers synthetic function
what is thrombophilia
too much clotting
there are elements of the clotting cascade that prevent over clotting, protein c, protein s and antithrombin.
antiphospholipid syndrome or deficiency of protein c or s can lead to over clotting
what are some conditions featuring over clotting
pulmonary embolism (blood clot in the lung)
deep vein thrombosis (blood clots in the limbs, often in the leg)
what are the risk factors for thrombophilia
previous DVT/PE
prolonged immobility
plaster cast
combined oral contraceptive pill
surgical operation
acutely unwell eg sepsis
cancer
dehydration
pregnancy
how is thrombophilia managed
anticoagulant medications - making them a bleeding risk in dental practice
