Renal replacement therapy- Dialysis Flashcards
What does dialysis do?
Uses the principle of diffusion to allow the removal of toxins which build up in the blood
- urea
- potassium
- sodium
also allows the infusion of bicarbonate
How does it work biochemically?
The dialysing fluid has a low conc of K, Urea and Na but a high Conc of HCO3 and so solutes reach equilibrium across a semi-permable membrane and in this way K, Urea and Na are removed the blood and bicarbonate is added
how is excess water removed during dialysis?
via convection- the movement of water (and all solutes dissolved in it) across a semipermeable membrane in response to pressure gradient i.e filtration
how efficient is dialysis:
- pattern of treatment
- GFR?
- minimum of 4 hrs 3 times per week
- gives GFR of 10-20
Restrictions in dialysis (4)
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.
Banana’s, chocolate, Potatoes, Avocado
risk of hyperkalaemia
Phosphate
Low phosphate diet
Phosphate binders with meals (6-12 pills per day)
as phosphate poorly dialysed
Access to the circulation in dialysis?
- gold standard
- pros
- cons
- 2nd Option
- Pros
- Cons
Fistula
joins artery and vein to make an enlarged thick walled vein called an arteriovenous Fistula
-good blood flow & unlikely to cause infection
-Requires surgery
needs maturation of about 6 weeks before can be used
can limit blood flow to instal arm
risk of thrombosis
-Tunneled venous catheter
catheter inserted into a large vein: jugular, subclavian or femoral
-Easy to insert (usually)
Can be used immediately
-High risk of infection
Can cause damage to veins making placing replacements difficult
Become thrombosed
Tunneled venous catheter complications: infection
- progresses to (3)
- Investigations (3)
- treatment (2)
- endocarditis, discitis, death
- blood cultures, FBC and CRP, exit site swab
- vancomycin nd line exchange or removal
complications of dialysis? (5)
Fluid overload Blood leaks Loss of vascular access Hypokalaemia and cardiac arrest intradialytic hypotension (under filling of the intravascular space and low BP)
how does peritoneal dialysis work?
solute removal by diffusion of solute across the peritoneal membrane
water removal by osmosis (water moving to equalise a conc gradient )
this is driven by high glucose conc in the dialysate fluid
Describe the differences in solute conc between the peritoneal membrane
Capillaries:
high Na, urea, K, H2O moving accords membrane into the peritoneal fluid
low glucose conc
Peritoneal fluid:
High glucose conc to allow the movement of all the other ions
Low Na, urea, K, H2O
Name the 2 types of peritoneal dialysis and the pattern of use
CAPD- continuous peritoneal dialysis
4 bag exchanges per day
Fluid drained then fresh fluid instilled
1/2 hour per exchange
APD-automeated peritoneal dialysis
1 bag of fluid stays in all day
overnight machine drains in and out fluid for 9-10 hours per night
Main complications of peritoneal dialysis? (3)
- caused by
- treatment
Infection
Membrane failure
Hernia’s
infection -Peritonitis or Exit site infection Due to either contamination (Staphylococci, Streptococci, Diptheroids) Gut Bacteria Translocation (E.Coli, Klebseilla) -Culture PD Fluid Intraperitoneal Antibiotics May need Catheter removed
Membrane failure
- inability to remove enough water do become fluid overloaded
- Haemodialysis
Hernia’s
-increased intra abdominal pressure
hernia repair + smaller fill volumes
Metabolic complications of ESKD (4)
-causes
Bone mineral metabolism
-Phosphate retention
low Vit D
hypocalcaemia and raised PTH = hyperparathyroidism
Anaemia
- Epo deficiency
- iron deficiency
Na and water retention
accelerated CV disease
When to start dialysis
- blood indications
- symptoms
-resistant hyperkalaemia
GFR 45
unresponsive acidosis
-fatigue, itch, unresponsive fluid overload, nausea, vomiting, loss of appetite
if HD to rapid?
Disequilibrium syndrome
-Cerebral oedema and seizures
