Flashcards in Haematological system Deck (43)
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1
Anticoagulation: What is thrombosis?
Inappropriate blood coagulation within a vessel is called thrombosis
2
Anticoagulation: What is appropriate blood coagulation?
when blood escapes from a vessel (failure of this results in bleeding)
3
Anticoagulation: What are the two types of coagulation?
In the arterial circulation:
high pressure system
platelet rich
In the venous circulation:
low pressure system
fibrin rich
4
Anticoagulation: How is arterial thrombosis treated?
Antiplatelet
5
Anticoagulation: How is venous thrombosis treated?
Anticoagulant
6
Anticoagulation: What are 3 common anti platelet drugs? How do they work? What is the lifetime of the drug? What is the dose?
Aspirin
Inhibits cyclo-oxygenase (platelet enzyme) irreversibly
Act for lifetime of platelet ie 7-10 days
Dose 75-300mg per day
Clopidogrel
Blocks ADP receptor (on platelet surface) irreversibly
Acts for lifetime of platelet ie 7-10 days
Dose 75mg per day
Prasugrel
Blocks ADP receptor irreversibly
Acts for lifetime of platelet ie 7-10days
More rapid and consistent inhibition than clopidogrel
7
Anticoagulation: What type of medication does not have to be stopped before dental procedures?
Antiplatelet
8
Anticoagulation: What are the common anticoagulants and via what route are they taken?
Intravenous
Unfractionated heparin
Subcutaneous
Low molecular weight heparins eg enoxaparin, tinzaparin, dalteparin
Oral
Warfarin, dabigatran, rivaroxaban, apixaban, edoxaban
9
Anticoagulation: What does heparin bind to?
Antithrombin which increases the activity of antithrombin
it's an indirect thrombin inhibitor as it enhances the activity of antithrombin
10
Anticoagulation: How is heparin given in hospital and monitored?
continuous infusion
APTT test - aim for ratio 1.8-2.8
11
Anticoagulation: What is low molecular weight heparin and how is it given? What is it used for?
Smaller molecule made from unfractionated heparin
Given subcutaneously
Renally excreted
Given once daily. Weight adjusted dosing
No monitoring necessary
Used for treatment and prophylaxis
In Sheffield – Dalteparin is used
12
Anticoagulation: When is low molecular weight heparin stopped and started after dental treatment?
For dental work give last dose 24 hours before dental surgery
Next dose 4 hours after dental surgery
13
Anticoagulation: What does warfarin inhibit?
factors II, VII, IX, X - 2, 7, 9, 10 (vitamin K dependent)
protein C and protein S
14
Anticoagulation: Where is warfarin metabolised?
the liver via cytochrome P450
15
Anticoagulation: When do the effects of warfarin start and continue after being stopped?
Peak effect 3-4 days after starting, and effect still present 4-5 days after stopping
ie slow on and slow off action
16
Anticoagulation: What drug may reduce warfarin binding to albumin?
phenytoin
17
Anticoagulation: What drug may inhibit hepatic microsomal degradation of warfarin?
Erythromycin - strong interaction, stays in blood stream longer - cerebral bleed
18
Anticoagulation: What drug may accelerate hepatic microsomal degradation of warfarin?
Carbamazepine
19
Anticoagulation: How is warfarin monitored?
The test to do is the INR (International Normalised Ratio)
Dose of warfarin based on the INR
Frequency of monitoring depends on the stability of the patient’s INR
eg can be 1 per week up to 1 every 8 weeks.
INR must be measured before surgery or invasive procedures
Can be measured using
a near patient testing device
Uses a drop of blood, similar
to blood glucose measurement
20
Anticoagulation: What is the anticoagulation target for treatment of DVT/PE (6 months) or AF?
2.0-3.0
21
Anticoagulation: What is the anticoagulation target for treatment of recurrent DVT/PE on warfarin life long and mechanical heart valves?
3.0-4.5
22
Anticoagulation: What are the side effects of warfarin?
Bleeding
Annual risk
3% any bleeding
1% serious / life-threatening
0.3% death due to bleeding
Skin necrosis (only at start of treatment)
Embryopathy (if used in first trimester of pregnancy
23
Anticoagulation: How is warfarin reversed?
Stop Warfarin
takes 2-3 days
Give vitamin K (iv,sc,o)
with iv preparation 80% correction in 6hrs
OR Give Fresh Frozen Plasma (FFP)
need large volume, only partial correction
or GIVE Clotting Factor Concentrate
Containing factors II, VII, IX, X
complete correction in 10minutes
24
Anticoagulation: What warnings are given to patients on warfarin?
No IM injections
No aspirin, NSAID without consultation
No contact sports – otherwise normal activities
Moderate alcohol intake is not harmful but excessive alcohol intake (binging) is
Significant changes in diet should be reported
Consult doctor or pharmacist before any new medication including over-the-counter drugs
25
Anticoagulation: When is it safe to perform an extraction on a patient taking warfarin?
iNR has to be less than 4.0
All patients must have INR within 24hr of extraction (in stable patients 72h will be OK)
Near patient testing devices give accurate results but must have documented good quality control
26
Anticoagulation: What are some new DOACs?
Rivaroxaban, Apixaban, Edoxaban (Xa inhibitors)
Dabigatran (Thrombin inhibitor)
- AF very common
All licensed for thromboprophylaxis after hip and knee surgery
May replace low molecular weight heparin for general thromboprophylaxis
Also licensed in treatment of thrombosis and atrial fibrillation
27
Anticoagulation: What are DOACs used for?
For prevention and treatment of thrombosis
Aiming to replace warfarin
28
Anticoagulation: What are the advantages of DOACs over warfarin?
Standard oral doses, not weight based
No monitoring
No alcohol or food interactions
Fewer drug interactions
No major adverse events other than bleeding
Half life 6-15 hours
29
Anticoagulation: What are the disadvantages of DOACs over warfarin?
Dabigatran mainly renally excreted
No antidote (exc for dabigatran)
More expensive than warfarin
30