CKD and kidney decline in the elderly Flashcards
what is the definition of CKD ?
abnormalities of kidney function or structure for more than three months with implications for health
how is absorption affected by age ?
the rate of absorption decreases. Gastric emptying is slower blood flow is slower.
The pH rises due to reduced number of parietal cells
how is distribution affected by age ?
Weight is lost as old people become frail therefore the volume of distribution decreases due to less SA .
how is metabolism affected by age ?
metabolic clearance decreases with age.
how is elimination affected by age?
renal clearance decreases because the rate of filtration decreases.
which means the half life of a drug increases so it takes the drug longer to reach steady state (Css)
how is distribution affected by CKD ?
volume of distribution increases due to oedema and reduced protein binding which means more free drug available
how is metabolism affected in CKD?
Overall get a decrease in metabolism due to the decreased activity of CYP enzyme.
But can get a short increase due to increased amount of free drug
what are some of the risks with administering drugs to a patient with CKD?
Toxicity and side effects due to build up renal excreted drugs.
Risk of infectiveness some drugs need a certain egfr to work
risk of exacerbating CKD and worsening renal function
what are the causes of CKD?
genetic malformations hypertension (kidneys overworking) glomelularnephritis - inflammation diabetes recurrent UTIs Lupus and other immune conditions Polysystic kidney disease obstructions
How do you treat impaired homeostatic kidney function?
- fluid restriction for oedema
- diuretics - only in CKD not AKI to offload excess fluid
- sodium bicarbonate to maintain oxygen potassium levels
- use ace inhibitors as they are nephroprotective
what is hyperkalemia and why how is it treated?
it is a high concentrations of K+ which can cause caridac arrhythmias
so aim to stabilise cardiac cells and reduce serum potassium
how do you stabilise cardiac cells in CKD?
10ml calcium gluconate IV slow bolus and repeat until ecg stabilises
how do you reduce serum potassium levels in CKD?
50ml of 50% glucose with 10 units of act rapid insulin over 10 mins - given at the same time to cancel each other
also consider 10-20mg of nebuliser salbutamol
why dose renal bone disease happen?
happens due to the disruption of parathyroid hormone, potassium,vitamin d and calcium
How is phosphate affected in CKD?
phosphate is normally excreted by renal tubules. so phosphate levels rise in the blood as it cannot be excreted
what does vitamin d do for the body?
its essential for good bone health by promoting GI absorption of calcium and renal tubular reabsorption of calcium aiding mineralisation of the bone
How is vitamin d affected in CKD?
vitamin d is activated in the kidney therefore there is reduced activation of vitamin d
Why can’t colecealciferol be taken by a patient with CKD?
It needs to be activated in the liver and the kidney by 2 hydroxylation reactions to get the active form so you cannot use it in renal impairment.
How is vitamin d affected in CKD?
high phosphate levels in the blood means that phosphate binds to circulation calcium un the blood .
Vitamin D is not activated so there is less calcium reabsorption
Overall calcium levels decrease.
what is parathyroid hormone?
it is responsible for the homeostasis of calcium in the blood
How is parathyroid hormone affected in CKD?
low levels of Ca2+ and activated vitamin D in the blood causes the release of PTH
PTH increases bone turnover to get calcium out of the bones and rises calcium levels in the blood causing brittle bones
How does PTH maintain calcium homeostasis ?
- it increases urinary excretion of phosphate so it binds less to ca2+ increasing serum calcium levels
- it decreases calcium excretion in the urine increasing calcium serum concentrations
- increases vitamin d synthesis and activation
- increases bone turnover and release calcium stores from the bone
- when ca2+ and vitamin D levels increase they act as negative feedback to reduce PTH secretion
what is secondary hyperthyroidism ?
when the vitamin D receptors become reduced and there is reduced sensitivity to serum calcium levels so PTH continue to be secreted .
Now calcium levels are above normal range and it becomes tertiary hyperthyroidism
what is tertiary hyperthyroidism ?
the parathyroid is actin autonomously and drug treatment becomes difficult
what is a first line treatment for CKD ?
Managing the high phosphate levels by dietary restriction of phosphate rich foods
e.g. beans dairy or ham
what is a second line treatment for CKD ?
phosphate binder medications
can use calcium based and non calcium based
why does non calcium based phosphate binders not work in secondary hyperthyroidism?
As the patient already has high calcium levels and giving the patient more calcium will only increase the serum calcium level
why is vitamin D alfacalcidol prescribed?
suppresses PTH release when Ca2+ levels are low and PTH is still high an its not controlled by phosphate binders
what are calcimemetics ?
they mimic the action of Ca2+ on the receptors of the parathyroid gland decreasing PTH secretion.
Have very strict prescribing guidelines as they are expensive
commonly used in patients not fit for surgery and can be used in combination with phosphate indoors and vitamin D.
what should be monitored during CKD treatment?
PTH , calcium and vitamin D levels
what is erythropoietin ?
a growth factor that promotes red blood cell formation and releases reticulocytes from the bone marrow
What Is the treatment for anaemia ?
ESA’s which go into the bone marrow and stimulates the abc growth by mimicking the endogenous erythropoietin .
either subcutaneous injection , IV or via dialysis machine
what is restless legs
due to the build up of toxic waste products such as urea
what is the treatment for restless legs
using a pedal bike or clonazepam , ropinrol or gabapentin
