Blood clotting Flashcards
understand the components of the blood, understand the coagulation process, know how medications affect clotting
what are the stages of blood clotting?
6
injury
vascular phase
platelet phase (primary haemostasis)
coagulation phase (secondary haemostsis)
clot formation and stabilisation
clot dissociation
what occurs during the vascular phase?
3
vessel vasoconstricts
injury exposes collagen in vessel wall
release of factors from vessel lining - ADP (platelets), tissue factor, endothelins
what happens during the platelet phase?
4
exposed collagen, ADP and endothelin attract platelets
platelets adhere
platelets aggregate and release ADP and thromboxane A2 which attracts more platelets
platelets plug the vessel injury
what happens during the coagulation phase?
4
coagulation cascade - proteins that lead to clot formation
intrinsic - in blood stream
extrinsic - in vessel
fibrinolysis happens in parallel - clot breakdown
what medications affect clotting?
3
anti-platelets
anticoagulants
injectable heparin
what is aspirin used for? (75mg and 300mg)
75mg once a day
* secondary prevention for coronary heart disease and transient ischaemic attack
300mg
* given in acute MI/stroke
what is aspirin’s mechanism of action?
inhibits COX enzyme to reduce production of thromboxane A2, reducing platelet aggregation
what is warfarin used for? and what is its mechanism of action?
2
prosthetic heart valves
inhibits production of vitamin K which is essential for coagulation factors 2,7,9,10
what is the way of monitoring warfarin?
INR - international normalised ratio
blood test
what does warfarin interact with?
5
metronidazole
fluconazole
NSAIDs
alcohol
grapefruit
what drugs are included in DOACs and what are they used for?
4,3
edoxaban, apixaban, rivaroxaban, dibigatran
used for atrial fibrillation, PE and DVT
what are DOACs mechanism of action?
inhibits factor X of the coagulation cascade so clot cannot form
what are the advantages and disadvantages of warfarin and DOACs?
onset, dosing, food effect, interactions, monitoring, offset
what are examples of injectable anticoagulants?and what are they used for?
2,3
low Mr heparin - dalteparin, enoxaparin
given after birth or significant surgery or unable to take DOACs
what is the mechanism of action of injectable anticoagulants?
inhibits formation of factor Xa and thrombin so fibrin clot cannot form
what are the general principles when a patient is on anticoagulants?
8
consult with GP/senior dentist if unsure
delay dental treatment until anticoagulant finished if planned
plan treatment for early in week and day
atraumatic surgery, staged
consider packing and suturing
ensure bleeding has stopped
give post-operative instructions
advise pt to take paracetamol instead of NSAIDs
how does liver disease affect clotting?
3
reduced number of platelets and impaired function
results in tendency to bleed
impaired production of coagulation factors 1,2,5,7,9,10,11,13
thrombopoeitin TPO stimulates platelet production in liver
what is thrombocytopenia? what are the causes?
1,2
low platelets
reduced production
* B12/folic acid deficiency
* liver disease
* leukaemia
* chemotherapy
increased destruction
* immune driven
what is Von Willebrand disease?
2
inherited disease leading to abnormal and prolonged bleeding
absence of or defective von Willebrand disease
what are the three types of von Willebrand disease?
type 1: partial deficiency of VWD, most common, mild
type 2: reduced function of VWD
type 3: complete deficiency of VWD, most rare, severe
how do you cover VWD during dental treatment?
3
tranexamic acid mouthwash - mild
DDAVP/desmopressin - more likely to bleed
von Willebrand factor concentrate - severe
what is haemophilia? what are the different types? how do you manage?
x-linked recessive disease causing spontaneous bleeding into joints and significant bleeding after trauma
* haemophilia A - deficient factor 8 - DDAVP/desmopressin or factor 8 concentrate
* haemophilia B - deficient factor 9 - factor 9 concentrate
what should you avoid with LA with a patient with inherited bleeding disorders? what should you do instead?
try to avoid inferior alveolar nerve blocks = risk of bleeding from muscle
* buccal infiltration
* intra-papillary injections
* intra-ligamentary injections
what blood tests are related to clotting?
4
full blood count
liver function test
INR
coagulation screen
what does INR measure? what is the lab standard? what is the INR for a healthy person? what should INR be for dental treatment?
5
compares how long it takes for a pts blood to clot compared to lab standard: 2-4
higher number = longer to clot
healthy person = 1
should be <4 for treatment
what is thrombophilia? what can it be caused by?
2
over-clotting of blood
caused by: antiphospholipid syndrome, protein C/S deficiency
what elements of the clotting cascade prevent over-clotting?
3
protein C
protein S
antithrombin
what is pulmonary embolism (PE)?
blood clot in the lung
what is deep vein thrombosis (DVT)?
bood clot in the limbs - often leg
what are risk factors for thrombophilia?
9
previous PE/DVT
prolonged immobility
plaster casts
combined contraceptive pill
surgical operation
acutely unwell (sepsis)
cancer
dehydration
pregnancy
how is thrombophilia managed?
anticoagulants but can cause a bleeding risk in dental practice
