Renal: Dialysis

Question 1

At what GFR is dialysis considered?

Answer 1

Below 15ml/min with symptoms
Resistant hyperkalaemia
Urea over 40
Profound symptoms such as fatique, itch, nausea

Question 2

What is the purpose of dialysis?

Answer 2

To remove toxins from the blood and infuse in bicarbonate (through a semi permeable membrane)

Question 3

What is ultrafiltration?

Answer 3

Removal of excess fluid

Question 4

What is haemofiltration?

Answer 4

Used for critically ill patients and allows the removal of waste products using convection.

Question 5

How often do patients get dialysis?

Answer 5

For 4 hours 3 times a week.

Question 6

What fluid and diet restrictions do patients on dialysis have to follow?

Answer 6

Less than 1litre fluid a day (including food)
Low salt
Low potassium
Low phosphate intake + phosphate binders with every meal

Question 7

What sort of access do you need in dialysis?

Answer 7

Arteriovenous fistula. This requires surgery and 6 - 12 weeks of maturation before it can be used.

Question 8

What is the main organism that infects tunneled venous catheters (used in a dialysis)

Answer 8

Staph aureus. Treated with vancomycin +/- gentamicin

Question 9

Why do you get hypotension on dialysis?

Answer 9

Myocardial stunning due to the large volumes of water being removed in one go rather than continuously. This leads to under filling of the intravascular space and low blood pressure.

Question 10

What is peritoneal dialysis?

Answer 10

Solute removal by diffusion of solutes across the peritoneal membrane. The water is removed by osmosis driven by the high glucose concentration in dialysate fluid.

Question 11

What is the main complication of peritoneal dialysis?

Answer 11

• Peritnonitis or exit side infection due to contaimination (staph, strep) or gut bacteria (E coli, klebsiella)
• Peritoneal membrane failure (inability to remove enough water resulting in fluid overload or inability to remove enough solute leading to uraemia). This requires a switch to haemodialyisis.
• Hernias due to increased intra abdominal pressure

Question 12

What is disequilibrium syndrome and how can you reduce the risk of this happening?

Answer 12

Too rapid a correction of uraemia leading to cerebral oedema and seizures. This is avoided by gradually building up dialysis eg starting from 90 minutes and gradually building up to 4 hours.