Dialysis - single compartment model Flashcards
What is dialysis? (2)
- kidneys
filters blood
removes waste + excess fluid
waste + fluid = sent to bladder - dialysis = treatment replacing kidney function
if kidneys ≠ work @ all
≠ work as they should
What are the 2 types of dialysis?
- haemodialysis = cycles blood outside body to filter before entering body again
- peritoneal dialysis = dialyser fluid fills peritoneal cavity
waste flows out according to concent. gradient
Why is dialysis similar to pharmacology? (3)
clearing of soluble waste
protein intake instead of injection
mechanisms = similar
What is urea?
urea = by-product of protein metabolism
= indicates renal function
= consider concent = mol/L
level = absolute amt
BUT = measured from small amt body fluid
greater amt urea ——>
worse renal function
What are the assumptions of dialysis? (2)
- single compartment
total body water (TBW) - 42L
urea
easily traverse membranes
est equilib quickly
uniform distribution - urea produced = direct prop. to protein intake
What is the LRD for the dialysis model?
LRDS for Dialysis vs Pharmacokinetics:
What are the additional assumptions?
≠ residual renal function
only 1 mechanism of renal dialysis
≠ water removed/added
simple to read only urea
Example
You have a patient suffering from acute kidney injury causing a build-up of waste products, such as urea, in the body. After monitoring your patient you can tell that their urea production rate is 6.3 mmol/hour and you assume their total body water is 42L. It is important that the patient is started on dialysis urgently to clear the body of excess urea. You decide on a dialysis regime of 3 times a week (Mondays, Wednesdays and Fridays) for 4 hours per session starting at 10h00. The dialyzer clearance rate is set to 200mL/min. Prior to the patient’s first treatment, you measure the initial urea concentration to be 30 mmol/L
What does the LRD look like?
Which functions can you use for urea elimination rate?
What does the pulse train function look like for the example?
Monday =
Wednesday =
Friday =
Height =
[urea] * dialyzer clearance
What does the LRD look like with drug administration?
What does the graph for clearance administration look like?
What does the graph look like for urea elimination rate?
What does the graph look like for urea concentration?
What is the formula for urea concentration?
