Dialysis Flashcards
all patients with CKD will end up with ESKD without treatment T or F
F, most will probably die before then
name the 3 concepts of dialysis
diffusion
convection
adsorption
why is diffusion used in dialysis?
allows toxins that build up to exit the blood eg urea, K+, Na+
what do you want to infuse in dialysis and why?
bicarb to fix metabolic acidosis
what substances do you want to remove in dialysis?
K
urea
Na
creatinine
what does a dialysis machine try to imitate?
a functional kidney
how much Na do you want to remove and why?
not much as dont want lots of salt and water to leave
what is ultrafiltration?
solutes moving with water across a semi-permeable membrane in response to a pressure gradient
what happens in a high flux membrane?
pores get bigger to allow bigger substances eg protein bound solutes in
a high flux membrane is present at what stage of dialysis?
adsorption
plasma protein movement across the membrane is principally achieved in what stage of dialysis?
adsorption
what is a convective solute drag?
dissolved solutes in water will move with it in response to pressure
dialysis only has access to the ___ of the body
circulation
haemodialysis is primarily a __ process
diffusive
haemodiafiltration is primarily a __ process
convective
haemodiafiltration relies on what process?
convective solute drag
what affects how well a substance is transported across the membrane in HDF?
water flux membrane pore size (big/small holes) pressure difference viscosity size, shape and charge of molecule
minimum dialysis time per week?
4hrs 3 times per week
what dietary changes does a patient on dialysis have to make?
low salt diet
low potassium diet
if anuric can only drink 1l of water
low phosphate diet
gold standard method of accessing the circulation for dialysis?
fistula
what is a fistula?
joining and artery and a vein to make an enlarged vessel - the arteriovenous fistula (AVF)
most common vessels chosen for a fistula?
brachial artery and cephalic vein
what was the original form of circulatory access for dialysis?
scribner shunt
complications of an arteriovenous fistula?
steal syndrome - ischaemia of the hand
what dialysis circulatory access is used for late presenting patients?
tunnelled venous catheter
what circulatory dialysis access method puts the patient at highest risk of infection?
tunnelled venous catheter
what vein is the tunnelled venous catheter inserted into?
jugular or subclavian vein
untreated tunnelled venous catheter infection can lead to what problems?
endocarditis
discitis
death
what organism is most likely to cause a tunnel venous catheter infection?
staph aureus or other gram +ves
Tx of a tunnelled venous catheter infection?
vancomycin +/- gentamicin
main complications of dialysis?
hypotension blood leaks from fistulae loss of vascular access hyperkalaemia cardiac arrest
what causes hypotension in dialysis patients?
myocardial stunning from dialysis
losing large volumes of water
how is solute removed in peritoneal dialysis?
diffusion
how is water removes in peritoneal dialysis?
osmosis
what drives the water out in peritoneal dialysis?
the high glucose conc in dialysate fluid
does glucose move in or out of the peritoneal cavity in peritoneal dialysis?
in
standard prescription of continual peritoneal dialysis?
4 2l bag exchanges per day
how is automated peritoneal dialysis different from continual?
only 1 bag is used rather than 4
main complications of peritoneal dialysis?
infection
peritoneal membrane failure
hernias (inc abdo pressure)
what investigation should you do for a peritonitis caused by dialysis?
culture peritoneal dialysate fluid
how long should the first HD session be? what should this build up to
2hrs
build up to 4hrs
what medical conditions should prompt withdrawal from dialysis?
PVD
stroke
CVD
cancer
