ECGs/arrithmiyas Flashcards
Explain the mechanism of the direct Xa inhibitors
commonly used - rivaroxaban and apixiban
of note only ONE enzyme is blocked
Explain the mechanism of dabigitran
oral direct thrombin inhibitor
of note only ONE enzyme is blocked
When might a measured creatinine clearance become relevant?
patients with extremes of body size or composition. In these settings, a Cockcroft-Gault formula can also be used
What is the creatinine clearance a marker of ?
reduced eGFR as it is hard to meausure eGFR directly
Explain the approach to enoxaparin dosing in relation to the creatinine clearance
- CrCL >30 = enoxaparin 40mg SC
- CrCL <30 = enoxaparin 20mg SC
If a patient has a CrCl <30 and requires long-term anticoagulation, what is the preferred medication?
warfarin
Provide 2 clinical scenarios where warfarin would be the preferred option over a DOAC
- pregnancy (limited evidence)
- mechanical heart valve (DOACs have a higher risk of valve thrombosis)
A patient with AF has impaired kidney function, but a CrCL>30. Which would be the best DOAC to prescribe and why?
The approximate degrees of excretion by the kidney are as follows:
- Dabigatran – 80 to 85 percent
- Rivaroxaban – 35 percent
- Apixaban – 25 percent
Therefore apixiban, as it is least dependent on the kidney for excretion
As per the AMH guidelines, what are the contraindications for DOACs in the setting of kidney disease?
- if CrCl<30
- reduced dose for CrCl between 30-50
A 90 year old man, weighing 55kg has AF and his GP would like to commence apixiban. What is the appropriate dose
3 criteria. If 2 or more are met, a lower dose of apixiban should be prescribed (i.e. 2.5mg BD)
- age >80
- body weight <60
- serum Creat >1.5 (133)
In a patient with a normal weight, what would be the rough CrCl if Creat was 100 or 200
100 - CrCL 20
200 - CrCL - 10
A 80y male with a CrCl of 20 would like to have dabigitran. It should be prescribed. True or False?
False
> for patients with CrCl >30 - give
> CrCl 15-30 usually avoided
List 3 relative contraindications to anticoagulation*
- cancer- these patients have a higher risk of anticoagulation related bleeding
- poorly controlled or untreated hypertension
- Previous history of intracranial hemorrhage
- Recent history of a major extracranial bleed without known cause
- History of peptic ulceration within the past three months.
- Recent history of repeated falling episodes with a patient at a higher risk for bleeds > ikelihood of poor patient compliance due to dementia or cognitive impairment, particularly in cases when there is no available caretaker.
- Alcoholism, especially binge drinking
Poorly controlled or untreated hypertension
Describe a scenario where the serum creatinine could be underestimated?
- possible in children, women, elderly and malnourished
- this is because creatinine generation from the muscles is proportional to the total muscle mass and catbolism
For example, the GFR may be reduced as low as 20-30 mL/min in a small elderly woman, while her serum creatinine remains in the upper range of normal.
Describe three examples that would cause the creatinine to be overstimated
- eating cooked meat
- ketosis
- hyperbilirubinaemia
- cephlasporins
- trimethoprim
- body building
- renal disease
what is the calculated creatinine clearance and why is it useful?
- serum creatinine is so highly dependent on age, sex and body size, a number of corrections and formulae have been developed to estimate the muscle mass and assumed creatinine production The most well-known formula is the Cockcroft-Gault formula
> good estimate of GFR
> inaccurate if larger body mass OR renal function is very impaired (i.e. GFR <20 mL/min). In these circumstances an isotopic method can be used if the GFR needs to be accurately measured.
what is the method used if an extremely accurate eGFR is required?
Isotopic methods can be used if a very accurate measurement of the GFR is required.
