Dialysis Handbook Flashcards
Explain the difference between hemodialysis and hemofiltration
hemofiltration uses water movement dragging middle size molecules via convection
hemodialysis uses diffusion - i.e., concentration gradient to move small molecular size molecules
What is the coefficient of ultrafiltration (KUF)?
number of mililiters of fluid transferred across the dialyzer membrane per hour when 1 mm Hg of transmembrane pressure is applied
higher KUF - less pressure needed
What is URR?
Urea Reduction Ratio
URR = (preBUN - postBUN) / preBUN
used to measure hemodialysis clearance
Where should the hemodialysis catheter be placed?
tip should be at the junction between CranVC and RA
What are the components of a dialysis prescription?
- modality (IMH vs CRRT)
- schedule
- intensity
- dialyzer type and size
- dialysate composition
- ultrafiltration rate
What is the difference between hemofiltration and ultrafiltration?
both use hydrostatic pressure to remove fluid and cause convective clearance of solutes but in ultrafiltration, as water removal is the goal, this is performed slow and without giving replacement fluid back
hemofiltration - fast rate to achieve much convection, but removed fluid needs to be replaced
Explain why fast hemodialysis rates don’t necessarily mean more efficient clearance
dialysate may not have time to be fully saturated while blood is passing
too fast rate»_space; not enough time for equilibration
What is a downside to pre-filter versus post-filter replacement in hemofiltration or hemodiafiltration?
pre-filter replacement –> decreases efficiency of solute removal
post-filter replacement –> increases risk of clotting in the filter
What is a relative contraindication for regional citrate anticoagulation?
liver failure
What are methods to determine adequacy of CRRT treatment?
- URR - should be > 65%
- Time-averaged urea concentration (TAC)
- Kt/V - K is clearance of the dialyzer, t is the time of dialysis, V is the volume of distribution
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