Anticoagulants Flashcards
examples of vitamin k antagonists
warfarin, acenucoumerol and phenindione
how long do vit k antagonists take to work
48 to 72 hours
What to give if immediate anticoagulant effect required
give with LMWH or UH
Target INR
n INR which is within 0.5 units of the target value is generally satisfactory; larger deviations require dosage adjustment. Target values (rather than ranges) are now recommended.
INR 2.5 for:
treatment of deep-vein thrombosis or pulmonary embolism (including those associated with antiphospholipid syndrome or for recurrence in patients no longer receiving warfarin sodium)
atrial fibrillation
cardioversion—target INR should be achieved at least 3 weeks before cardioversion and anticoagulation should continue for at least 4 weeks after the procedure (higher target values, such as an INR of 3, can be used for up to 4 weeks before the procedure to avoid cancellations due to low INR)
dilated cardiomyopathy
mitral stenosis or regurgitation in patients with either atrial fibrillation, a history of systemic embolism, a left atrial thrombus, or an enlarged left atrium
bioprosthetic heart valves in the mitral position (treat for 3 months), or in patients with a history of systemic embolism (treat for at least 3 months), or with a left atrial thrombus at surgery (treat until clot resolves), or with other risk factors (e.g. atrial fibrillation or a low ventricular ejection fraction) [note: NICE guideline NG208 (Heart valve disease presenting in adults: investigation and management, November 2021) does not recommend anticoagulation after surgical biological heart valve replacement unless there is another indication for anticoagulation.]
acute arterial embolism requiring embolectomy (consider long-term treatment)
myocardial infarction
INR 3.5 for:
recurrent deep-vein thrombosis or pulmonary embolism in patients currently receiving anticoagulation and with an INR above 2;
Mechanical prosthetic heart valves:
the recommended target INR depends on the type and location of the valve, and patient-related risk factors
consider increasing the INR target or adding an antiplatelet drug, if an embolic event occurs whilst anticoagulated at the target INR.
role of vit k
blood clotting and wound healing
Monitoring before warfarin
baseline prothrombin time (INR)
acceptable INR deviation
within 0.5 of the target value
what condition has a target INR of 3.5
recurrent DVT and PE despite anticoagulant therapy
why are anticoagulants less effective I treating clots in arteries than veins
clots I arteries are formed mainly of platelets and not fibrin
what happens if patient experiences embolism despite being at target INR
consider increasing INR
duration of warfarin for DVT and PE
isolated calf vein DVT - 6 weeks
VTE provoked by surgery or other transient risk factors : 3 months
unprovoked proximal DVT and PE - at least 3 months
treating haemorrhage and elevated INR
Greater than 8 with minor bleeding — stop warfarin and give phytomenadione by slow intravenous injection. The dose of phytomenadione may be repeated after 24 hours if the INR is still too high.
Restart warfarin when the INR is less than 5.
Greater than 8 with no bleeding — stop warfarin and give phytomenadione by mouth using the intravenous preparation orally (off-label use). The dose of phytomenadione may be repeated after 24 hours if the INR is still too high.
Restart warfarin when the INR is less than 5.
Between 5–8 with minor bleeding — stop warfarin and give phytomenadione by slow intravenous injection.
Restart warfarin when the INR is less than 5.
Between 5–8 with no bleeding — withhold 1 or 2 doses of warfarin and reduce subsequent maintenance dose.
If there is unexpected bleeding at therapeutic levels — always investigate possibility of underlying cause, such as unsuspected renal or gastrointestinal tract pathology.
when do you stop warfarin before surgery
Max INR for Minor surgical procedures with low risk of bleeding
5 days before surgery
Minor surgical procedures with low risk of bleeding can be performed in general with an international normalized ratio (INR) of less than 2.5. However, local recommendations should be considered.
when should warfarin restarted after surgery
on the evening of the surgery or the next day
how does LMWH bridging work for patients who are high risk of VTE and taking warfarin.
interim therapy with LMWH prior to surgery but this must be stopped at least 24 hours before surgery
if high risk bleeding surgery - restart LMWH after at least 48 hours
what is the protocol emergency surgery on patients taking warfarin
delay for 6- 12 hours and give IV vit k
if not possible to delay - give IV vit K and dried prothrombin complex and check INR before surgery
side effects of warfarin
bleeding -
calciphylaxis -
monitoring of warfarin
initial baseline prothrombin
side effects of warfarin
bleeding - small increase can trigger bleeding from thing like peptic ulcer and major devotion can cause spontaneous
nose bleeds
calciphylaxis - can lead to blood clots and skin ulcers
monitoring of warfarin
initial baseline prothrombin
INR - daily or every other day until stable dose and inr
then changes in patient clinical condition deteriorates ( intercurrent illness increase INR measurement requirements
