Bleeding, leukaemia and dentistry Flashcards
process of haemostasis
injury/ tissue damage –> vascular response –> platelet adhesion, aggregation –> unstable platelet clot –> coagulation factor cascade –> fibrin –> stable clot
draw clotting cascade
see lecture
what is the vascular response of haemostasis
vasoconstriction
what is the platelet response of haemostasis
von willebrand factor + platelet + fibrinogen –> unstable platelet clot
–> clotting cascade –> fibrin –> stable clot
why should dentists be aware of haemophilia
more bleeding, esp with extractions
2 considerations of injections with haemophiliac pts
- blocks/ FOM injections may cause haemorrhage to track through tissue planes –> airway obstruction
- avoid intramuscular injections
when is heparin used
acute thromboembolism
when is enoxaparin used and how does it work
prophylaxis for DVT/ PE
LMW heparin, inhibits factor Xa
how does warfarin work
impairs vit K synthesis dependent coagulation factors (2,7,9,10) in the LIVER
how long does warfarin take to become effective
2-4 days
7 indications of oral anticoagulation SHORT TERM
- prophylaxis to prevent DVT
- myocardial infarction (3 months)
- established DVT (3 months)
- xenograft heart valves (3 months)
- pulmonary embolism (6 months)
- coronary artery bypass grafts (CABG, 2 months)
- atrial fibrillation
3 indications of oral anticoagulants LONG TERM
- recurrent venous thromboembolism
- rheumatic heart diease and atrial fibrillation
- cardiac prosthetic valve replacement and arterial grafts
what is used to measure anticoagulant effect, how to caculate
INR = prothrombin time (test)/ prothrombin time (control)
INR values
1= normal
2.5= DVT, PE, AF
3.5= recurrent DVT/ PE, mechanical heart valves
>4=dop not extract
when must INR be checked
on the day/ no more than 24-36 hours before procedure
3 warfarin potentiating factors
- antibiotics
- miconazole oral gel (antifungal)
- aspirin/ NSAIDS
5 relevant drug interactions/ considerations with warfarin
- amoxicillin (single 3g dose ok)
- metronidazole (halves effect of warfarin)
- erythromycin (unpredictable, only affects some pts
- NSAIDs (inc bleeding, GI bleeds)
- daktarin oral gel
when and why alter INR 2
before surgery to decrease bleeding (NOT by dentists)
- stop meds 48hrs before surgery
- reduce warfarin by 50% for 48hrs
2 new anti-coagulants and how they work/ when used
rivaroxaban: Xa inhibitor, prophylaxis for hip/ knee repacement
dabigatran: direct thrombin inhibitor, prophylaxis for hip/knee replacement, stroke, AF, valve replacement
what is normal bleeding time
compare genders
2-10 mins
longer in women than men
effect of antiplatelet agents on
a. bleeding time
b. haemostasis
a. bleeding time: prolongs
b. haemostasis: minimal effect
5 coagulation defects causes
- liver disease
- hepatocellular failure
- vit k deficiency
- increased fibrinolysis
- thrombocytopenia
healthy platelet count
150-450000 per microlitre
symptoms of thrombocytopenia
100-150m bleeding time
x20-100 increase in bleeding time
x20 risk of spontaneous bleeding
