Renal Replacement Therapy GUIDE WITH EXAM QUESTIONS AND ANSWERS

Renal Replacement
Therapy GUIDE WITH
EXAM QUESTIONS AND
ANSWERS
Renal Replacement Therapy is also known as dialysis
• Conservative therapy such as diet, medication, and fluid
restriction are no longer managing the patient’s
symptoms effectively and the patient’s renal failure is
causing potentially life-threatening complications
• Dialysis is a treatment that can sustain life in both acute
and chronic renal failure
Renal Failure accomplishes 3 purposes
• Restores fluid and electrolyte balance
• Removes waste and toxic material from the body
• Controls acid-base balance
We normally see this used in the chronic renal population but
we may need urgent treatment to get us into the diuretic
phase to get into recovery during emergent crises. In HD
normal treatment lasts 3-5 hours and is 3x a week.
The process of dialysis regardless of type is based on 3
principles
• Diffusion
• Osmosis
• Ultrafiltration
Diffusion is
• Movement of particles from an area of greater concentration
to an area of lesser concentration (across a semi-permeable
membrane)
• Movement of electrolytes of metabolic waste; the lesser
state is a dialysate and the membrane is the dialyzer
The diffusion rate is affected by
• Size of membrane pores
• Amount of surface area of membrane
• The temperature of the solutions
• Differences in solute concentrations
What happens in diffusion related to dialysis?
• As a result of diffusion in dialysis urea, creatinine, potassium,
phosphate, and uric acid are removed from the patient’s
blood into the dialysate
• Dialysate is the fluid that is utilized
• Proteins and RBCs are not lost from the blood because
they are too large to pass through the semi-permeable
membrane
What is osmosis?
• Movement of water across a semi-permeable membrane

, from an area of lesser concentration to an area of greater
concentration of particles
• Movement of water of lesser concentration to an area of
greater
• Osmosis specifically will remove fluid related to peritoneal
dialysis

What is Ultrafiltration?
• Movement of fluid across a semi-permeable membrane
as a result of an artificially created pressure gradient
• More efficient than osmosis for the removal of fluid
• Used in HD instead of osmosis
• Need positive or negative pressure to cause the removal of
fluid
• This is related to HD because we are using pressure
What is happening in hemodialysis?
• During hemodialysis blood and dialysate flow in
opposdirectionstion within their compartments on either
side of an enclosed semi-permeable membrane
• Waste products move from the blood into the dialysate
through diffusion
• Excess water moves out of the blood into dialysate by
applying a positive or negative pressure to the system
• Happens in HD, PD, and CRRT
Components of the hemodialysis system
• Dialyzer (artificial kidney)
• Dialysate
• Hemodialysis machine
• Vascular access routes-where we are putting blood back into
the patient
HD Dialyzers
• A plastic cartridge containing thousands of parallel hollow
tubes or fibers
• Fibers are semipermeable membranes
• Act as an artificial kidney and replace kidney function that is
lacking
• That is what blood is going to be flowing through
The Dialysate
• Made from clear water
• free of metabolic waste products or drugs
• DOES NOT HAVE TO BE STERILE BECAUSE BACTERIA
MOLECULES ARE TOO LARGE TO PASS THROUGH A SEMI-
PERMEABLE MEMBRANE
• The composition of dialysate is based on patients
needs; MD orders the exact composition
HD Machine Role