Dialysis

Question 1

What is diffusion in dialysis?

Answer 1

Movement of solutes from a high to low concentration

Gradient will equalize to form an equilibrium

Question 2

What is dialysis used for?

Answer 2

Allows removal of toxins that build up in CKD:
Urea
Potassium
Sodium
Allows the infusion of bicarbonate and calcium

Question 3

What blood flow rate is needed for haemodialysis?

Answer 3

300-350 mls/min

Question 4

What is commonly included in dialysate?

Answer 4

Pure water
Na 138
HCO3 38
K 2-4
Glucose 5

Question 5

What is convection?

Answer 5

Movement of water and all solutes dissolved in it across a semi-permeable membrane in response to a pressure gradient

Question 6

What is adsorption concerned with?

Answer 6

Plasma proteins and any solutes bound to them
Plasma proteins stick to the membrane surface and are removed by membrane binding
High flux membranes adsorb protein-bound solutes better than low flux membranes

Question 7

What mechanisms does hemodiafiltration rely on?

Answer 7

Increasingly convective
The greater the convective force, the greater will be the generated volume of pressure-driven ultrafiltrate
Large volumes of ultrafiltrate add to solute drag

Question 8

What affects the convective transport of a molecule across a membrane?

Answer 8

Water flux (rate and volume) 
Membrane pore size (big or little holes)
Pressure difference (hydrostatic pressure) 
Viscosity of hte fluid 
Size, shape and electrical charge

Question 9

What is the difference between haemodialysis and hemodiafiltration?

Answer 9

Replacement of extra-convective ultrafiltrate throughout the dialysis period (minus any intended ultrafiltration volume)
As this replacement fluid must be given back directly to the patients circulation, the composition and purity of this fluid is pivotal

Question 10

What restrictions does dialysis put on the patient?

Answer 10

Fluid - if anurinc needs to be 1litre per day (including food based fluid)
Salt - low salt diet to reduce thirst and help fluid balance
Low potassium diet
Low phosphate diet

Question 11

What foods contain high levels of potassium?

Answer 11

Banana
Chocolate
Potato
Avocado

Question 12

Where is a tunneled venous catheter commonly inserted into?

Answer 12

Internal jugular vein

Question 13

What will commonly infect lines?

Answer 13

Staph aureus

Question 14

Where can s. aureau seed?

Answer 14

Endocarditis
Discitis
Death

Question 15

What is the treatment for line infections?

Answer 15

Vancomycin +/- gentamicin

Question 16

What is the gold standard for dialysis vascular access?

Answer 16

Fistula - artery and vein surgically connected - venous part will develop to create an enlarged, thick walled vessel called an arteriovenous fistula

Question 17

Where are common sites for fistulas?

Answer 17

Radio-cephalic
Brachio-cephalic
Brachio-basilic transposition

Question 18

What can go wrong with dialysis?

Answer 18

Hypotension
Haemorrhage
Loss of vascular access
Arrhythmia
Cardiac arrest

Question 19

How does peritoneal dialysis work?

Answer 19

Solute removal via diffusion of solutes across the peritoneal membrane
Water removal via osmosis driven by a high glucose concentration in dialysate fluid

Question 20

What infections can complicated peritoneal dialysis?

Answer 20

Peritonitis or exit site infection
Contamination: staphylococci, streptococci, diphtheroids
Gut bacteria translocation: e.coli, klebsiella

Question 21

What is the management of peritoneal dialysis?

Answer 21

Culture PD fluid
Intra-peritoneal antibiotics (gram positive, gram negative)
May need catheter removal

Question 22

What is peritoneal membrane failure?

Answer 22

Inability to remove enough water - fluid overloaded
Inability to remove solutes
Requires switch to HD

Question 23

When should dialysis be started?

Answer 23

Resistant hyperkalaemia
eGFR <7 ml/min
Urea >40 mmol/L
Unresponsive metabolic acidosis

Question 24

What symptoms should prompt you to start dialysis?

Answer 24

Nausea
Anorexia
Vomiting
Profound fatigue
Itch
Unresponsive fluid overload

Question 25

How is dialysis started?

Answer 25

1st session 90-120 in

Subsequent sessions up to 4 hours

Question 26

What can occur with a too rapid correction of uraemic toxin levels?

Answer 26

Disequilibrium syndrome: cerebral oedema, confusion, seizures and death

Question 27

Why will dialysis be drawn from a patient?

Answer 27

Haemodynamic instability
Progressive dementia
Inability to remain on therapy for full duration
CV event
Terminal cancer
Increasing fragility and inability to cope at home