Renal replacement therapy Flashcards
What does dialysis do to the blood?
Removes toxins: urea, potassium, sodium
Allows infusion of bicarbonate
How does dialysis achieve removal of toxins and infusion of bicarbonate?
Diffusion via a semi-permeable membrane
How does haemodialysis get rid of water?
Convection/filtration:
The movement of water (and all solutes dissolved in it) across a semipermeable membrane in response to a pressure gradient
What is the minimum weekly amount of dialysis given to patients?
4 hours 3x weekly
What substances must patients reduce intake of when on dialysis and how is this achieved?
Fluid: if anuric 1litre per day (including food based fluid)
Salt: low salt diet to reduce thirst and help with fluid balance
Potassium: low potassium diet (bananas, chocolate, potatoes, avocado)
Phosphate: low phosphate diet and phosphate binders with meals (6-12 pills per day)
Why must patients restict intake of certain substances while on dialysis?
Kidneys normally excrete these things: on dialysis with kidneys not working, it is difficult ot remove them from the system
What is the gold standard method of creating vascular access for dialysis?
Creating an arteriovenous fistula
What are the benefits of creating an arteriovenous fistula for vascular access?
Good blood flow
Reduced likelihood of infection
What are the disadvantages of creating an arteriovenous fistula for vascular access?
Requires surgery
Requires maturation of about 6 weeks before can be used
Can limit blood flow to distal arm “steal”
Can block
How is a tunneled venous catheter used to get vascular access for dialysis?
A catheter inserted into a large vein: jugular, subclavian or femoral
What are the advantages of using a tunneled venous catheter for vascular dialysis access?
Usually easy to insert
Can be used immediately
What are the disadvantages of using a tunneled venous catheter for dialysis access?
High risk of infection
Can cause damage to veins making placing replacements difficult
Become blocked
What are the complications of an untreated infection from a tunneled venous catheter?
Endocarditis
Discitis
Death
What investigations should be done when infected tunneled venous catheter suspected?
Blood Cultures
FBC and CRP
Exit site swab
What is the treatment for an infected tunneled venous catheter?
Antibiotics: vancomycin
Line removal or exchange
What are some of the complications of haemodialysis?
Fluid overload
Blood leaks
Loss of vascular access
Hypokalaemia and cardiac arrest
Intradialytic hypotension
Why does interdialytic hypotension occur as a complication of haemodialysis?
Removing large volumes of H20 three times per week rather than continuously with normal kidneys leads to underfilling of the intravascular space and low BP
How does peritoneal dialysis work?
Solute removal by diffusion of solutes across the peritoneal membrane
Water removal by osmosis (water moving to equalise a concentration gradient) driven by high glucose concentration in dialysate fluid
What is involved in continuous peritoneal dialysis (CAPD)?
Four bag exchanges per day
Fluid drained then fresh fluid instilled
½ hour per exchange
What is involved in automated peritoneal dialysis?
1 bag of fluid stays in all day
Overnight machine drains in and out fluid for 9-10 hours per night
What are the complications of intraperitoneal dialysis?
Infection
Membrane failure
Hernias
What kinds of infection might occur with intraperitoneal dialysis?
Peritonitis
Exit site infection
What are the causal organisms of infection with intraperitoneal dialysis?
Contamination: staphylococci, streptococci, diptheroids
Gut bacteria translocation: E. Coli, klebsiella
What is the treatment for intraperitoneal dialysis infection?
Culture PD fluid
Intraperitoneal antibiotics
May need catheter removed
What is membrane failure associated with intraperitoneal dialysis?
Inability to remove enough water so the patient becomes fluid overloaded
How is membrane failure associated with intraperitoneal dialysis managed?
Requires switch to haemodialysis
What blood results might indicate a patient needs to be started on dialysis?
Resistant hyperkalaemia
GFR <5
Urea >45
Unresponsive acidosis
Is there any difference in mortality if dialysis started earlier?
No
How long is the first session of haemodialysis?
2 hours
