Lect 6 Flashcards
hemodialysis
blood is removed from the body, filtered, then put back into the body
peritoneal dialysis
Used peritoneal layer/ membrane act as a membrane inside the body then empty out peritoneal cavity and replace more fluid
KDOQI recommendation for planning dialysis
Stage 4 CKD or CrCl less than 30 mL/min
when is dialysis access created?
GFR less than 25 mL/min
SCr >4
1 year prior to anticipated need for dialysis
when does KDOQI recommend evaluating for dialysis?
GFR or CrCl less than 15 mL/min/1.73 m2
when is dialysis access created?
GFR 4
1 year prior to anticipated need for dialysis
when does KDOQI recommend evaluating for dialysis?
GFR or CrCl
indications for dialysis
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how do you evaluate uremia?
BUN
what are the basic principles of diffusion in hemodialysis?
molecular weight, conc gradient, memb resistance, blood and dialysate flow rates
what are the basic principles of ultrafiltration in hemodialysis?
transmembrane pressure (TMP), ultrafiltration coefficient (Kuf)
conventional or standard dialyzers
small pores limit clearance to small molecules (urea and creatinine)
low blood flow rates
high efficiency dialyzers
large surface area (so increase capacity to remove water, urea, small molecules)
high blood flow rates
high flux dialyzers
large pores increase removal of high mol-weight substances
high blood flow rates
high flux dialyzers
large pores increase removal of high mol-weight substances
high blood flow rates
what is the dialysate solution composed of?
purified water and electrolytes (glucose, Na, K, Ca) –> actual quantities specified by physician
similar to body fluids but lacking waste products
dialysis solution bases
added to neutralize acid (since normal metabolism prod acids that ESRD pts are unable to clear)
examples of dialysis solution bases
- acetate= converted by liver to bicarb; has more adverse effects
- bicarbonate= $$$, drug of choice in liver impairment and severe acidosis
what is the major challenge for success and long-term feasibility of HD?
vascular access
AV fistula
anastomosis of a vein and artery
advantages of AV fistula
longest survival, lowest complications, increased survival and decreased hospitalizations, most cost-effective
disadvantages of AV fistula
takes 1-2 months to mature, diff to create in elderly or PVD pts
AV synthetic graft
graft connects the artery and vein
advantages of AV synthetic draft
easily implanted
longer survival than catheters
disadvantages of AV synthetic graft
shorter survival than fistula
higher rates of complications than fistulas
2-3 weeks to endothelialize prior to use
disadvantages of AV synthetic graft
shorter survival than fistula
higher rates of complications than fistulas
2-3 weeks to endothelialize prior to use
venous catheters
femoral, subclavian, or internal jugular vein
least desirable access
advantages of venous catheters
immediate use
easy to place and remove
disadvantages of venous catheters
short survival
higher risk of infection
may not provide adequate blood flow
urea reduction ratio
% of blood being cleared of urea
(predialysis BUN- postdialysis BUN) / predialysis BUN x 100
what is an adequate urea reduction ratio?
> 60%
Kt/V
unitless parameter
fraction of total body water cleared of urea
what is an adequate urea reduction ratio?
> 60%
measure monthly and adjust dialysis
Kt/V
unitless parameter
fraction of total body water cleared of urea
K= dialyzer clearance of urea
t= time
V= total volume of water in body (0.6 x weight in kg)
how do you interpret Kt/V?
mortality increases as Kt/V decreases
Kt/V of 1.2 is approx = URR of 63%
intermittent hemodialysis
PRN basis
most commonly: 3 sessions/week with 3-5 hours/session
continuous hemodialysis
based on access
hemodialysis pros and cons
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basic principles of diffusion in peritoneal dialysis
molecular weight
conc gradient
memb resistance
basic principles of ultrafiltration in peritoneal dialysis
osmotic force (dextrose and icodextrin)
what can you alter in peritoneal dialysis?
NOT BLOOD FLOW OR PERMEABILITY
dialysate volume
dwell time
exchanges per day
what can you alter in peritoneal dialysis?
NOT BLOOD FLOW OR PERMEABILITY
dialysate volume
dwell time
exchanges per day
continuous ambulatory peritoneal dialysis (CAPD)
manual dialysate exchanges
adv= independence
disadv= infection risk
automated peritoneal dialysis (APD)
automatic cycler performs exchanges (throughout the night)
adv= fewer exchanges in daytime, sterility, convenience
disadv= machine in bedroom
types of APD
- ) continuous cycling peritoneal dialysis (CCPD)
- ) tidal peritoneal dialysis
- ) nightly intermittent peritoneal dialysis
continuous cycling peritoneal dialysis (CCPD)
APD with “wet” day (long daytime dwell)
tidal peritoneal dialysis
initial partial fill, then drain, then replace
creates tidal flow
nightly intermittent peritoneal dialysis
APD with “dry” day (no daytime dwell)
intermittent peritoneal dialysis
normally reserved for acute pts
machine operator
high cost, high risk of infection
PD pros and cons
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