Dialysis

Question 1

Name three types of dialysis

Answer 1

• Haemodialysis
• Haemodiafiltration
• Peritoneal Dialysis

Question 2

What three process is dialysis based on?

Answer 2

Diffusion
Adsorption
Convection

Question 3

How is diffusion involved in dialysis?

Answer 3

Moves solutes from a high to low concentration allowing the removal of toxins and infusion of bicarbonate

Question 4

What is added/removed in dialysis?

Answer 4

Removed - urea, potassium, sodium, creatinine, toxins

Added - pure water, sodium, bicarbonate, potassium, glucose

Question 5

What rate does blood flow in dialysis?

Answer 5

300-350mls/min

Question 6

How does convection help dialysis?

Answer 6

Moves the water across the membrane in response to a pressure gradient

Question 7

What is ultrafiltration?

Answer 7

Convection solute drag pulls the solute with the water

Question 8

How does adsorption play a role in dialysis?

Answer 8

Affects plasma proteins and solutes bound to them. Proteins stick to the membrane and are removed by binding

Question 9

What time of membrane adsorbs protein better?

Answer 9

High flux membranes

Question 10

How is haemodiafiltration different?

Answer 10

Increasing convection allows a larger volume of ultra filtrate. This adds to the solute drag.

Question 11

Name the factors affecting efficiency of haemodialysis

Answer 11

• water flux
• membrane pore size
• pressure difference
• viscosity of fluid
• size/shape/charge of molecule

Question 12

If a lot of ultra filtrate is removed what must be done?

Answer 12

Replacement of extra-convective fluid

Question 13

Define high volume

Answer 13

> 20 litres

Question 14

How often is haemodialysis given?

Answer 14

4 hours 3 times a week

Question 15

What are the restrictions a patient but follow if on dialysis?

Answer 15

Fluid 1 litre a day
Low salt to help fluid balance
Low potassium
Low phosphate (with phosphate binders with meals)

Question 16

Name three ways vascular access can be obtained for dialysis

Answer 16

• tunneled venous catheter
• fistula
• haemodialysis reliable outflow graft

Question 17

Describe a tunnelled venous catheter

Answer 17

Inserted into large vein - typically internal jugular

Question 18

What are the pros of catheter?

Answer 18

Easy to insert and can be used immediately

Question 19

What are the cons of a catheter?

Answer 19

Infection (staph aureus can lead to endocarditis, discitis and death)
Blockage
Damage to central veins which may cause future problems

Question 20

How are catheter infections managed?

Answer 20

Blood cultures, FBC, CRP and exit site swab

Line should be removed and vancomycin +/- gentamicin

Question 21

Describe a fistula

Answer 21

Artery and vein surgically connected - the venous part develops to create an enlarged thick walled vessel known as an arteriovenous fistula

Question 22

Where can a fistula be formed?

Answer 22

Radio-cephalic
Brachio-cephalic
Brachia-basilic transposition

Question 23

What are the advantages of a fistula?

Answer 23

Good blood flow and lower risk of infection

Question 24

What are the disadvantages of a fistula?

Answer 24

Requires surgery and can take up to 12 weeks to be fit for use, can limit blood flow to distal arm, thrombose or stenose

Question 25

State five complications of haemodialysis

Answer 25

- hypotension (underselling of intravascular space) - haemorrhage (ruptured AVF) - loss of access (thrombosis/stenosis) - arrhythmia (electrolyte imbalance) - cardiac arrest

Question 26

How does peritoneal dialysis work?

Answer 26

Solute removal by diffusion across the peritoneal membrane. Water is removed by osmosis and driven by high glucose concentration in dialysate fluid

Question 27

What are the two types of peritoneal dialysis?

Answer 27

- continuous ambulatory | - automated

Question 28

Describe continuos ambulatory peritoneal dialysis

Answer 28

4 2 litre bag exchanges per day, each lasting 20-30 minutes. Dialysate is drained by gravity and discarded

Question 29

Describe automated peritoneal dialysis

Answer 29

1 bag of fluid stays in all day and overnight APD machine controls fluid drainage in and out for 9/10 hours

Question 30

What are the complications of peritoneal dialysis?

Answer 30

- infection - membrane failure - hernias

Question 31

How may infection arise in peritoneal dialysis?

Answer 31

Peritonitis or from exit site, contamination can occur (staph/strep/diptheroids) or translocation from gut (e.coli, klebsiella)

Question 32

What might happen if the membrane fails?

Answer 32

Unable to remove enough water or solute may need switched to HD

Question 33

Why does peritoneal dialysis increase risk of hernias?

Answer 33

Increased intra-abdominal pressure requires repair and smaller fill volumes

Question 34

When might dialysis be started?

Answer 34

``` Acute Kidney Injury eGFR<7ml/min Urea >40 Unresponsive metabolic acidosis/hyperkalaemia Systemic symptoms ```

Question 35

What happens if dialysis is too fast in the beginning?

Answer 35

Disequilibrium syndrome - cerebral oedema, confusion, seizures, death