1. Principles of Peritoneal Dialysis

2. Diffusion
Transfer by diffusion is the passive transfer of solutes across the membrane, without the passage of solvent (water). 1 2
Blood
Membrane
Dialysate
1 - Red blood cell
2 - Bacteria
Sodium
Potassium
Chloride
Bicarbonate
Beta 2-m
(Solute PM>5000)
Urea
Creatinine
Uric acid

3. Factors effecting diffusion
Membrane
Surface area, type, thickness
Blood film thickness
Dialysate flow configuration
Concentration gradient
Size of solute
Ultrafiltration
Temperature of dialysate
Qb - Blood flow rate
Qd - Dialysate flow rate
Time

4. Factors relevant to PD Membrane Surface area, type, thickness
Blood film thickness
Dialysate flow configuration
Concentration gradient
Size of solute
Ultrafiltration
Temperature of dialysate
Qb - Blood flow rate
Qd - Dialysate flow rate
Time

5. Weekly plasma clearances L/week

6. Solute Clearance in PD Factors that deliver clearance Total volume
Volume per exchange
Number of exchanges
Dwell time
Factors driving clearance requirements
Urea generation(diet, weight, metabolic rate)
Residual renal clearance(kidney function)
U.F. rate (solution tonicity, fluid intake)
Peritoneal membrane (permeability)

7. Osmosis
Movement of water from an area of low solute concentration to an area of high solute concentration.
Blood
mOsm/L
Dialysis solution
mOsm/L
Water
Solute

8. Ultrafiltration
CAPD

9. Ultrafiltration

10. Ultrafiltration

11. Clearance – Peritoneal Equilibration
Twardowski, University of Missouri

13. Process of PD Exchange CAPD Drain(<20 Minutes) Fill(<10 minutes)
Dwell - (CAPD = hours)
- (APD = 30mins – 2 hours)
CAPD
Manual
Day Time Exchanges
Procedure Every 4-8 Hours

14. Outline benefits of PD Medical Psycho-social Good BP control
Minimal cardiovascular stress
Sodium and water control
No heparin
Steady state chemistries
No vascular access
Better hematocrit
Good middle molecule
clearance
Psycho-social
Self care - control
Fewer dietary restrictions
Less travel to center
Easier to vacation
Easy to learn
No need for electricity or
running water

15. Disadvantages Medical Risk of infection Psycho-social
Peritoneal access
Less “effective” therapy
Biocompatibility of solutions
Long term impact on peritoneal membrane
Protein loss
Glucose absorption
Psycho-social
Self Care - control
“Constant” treatment
Body image-catheter, girth
Family commitment
Storage requirements

16. CAPD Benefits Continuous Therapy Volume Limitations 24 Time24
Time
High transporters will have poor UF
4 x per day exchange
IP pressure with large volumes
Optimum dialysis for low permeability
No night time Tx
Can perform anywhere
Ambulatory
Anywhere
4 - 5 Exchanges
Long Dwells

17. APD Benefits Optimum dialysis for High permeability No night time Tx
Intermittent
Therapy
Volume
Benefits
Limitations 24
Time
Optimum dialysis for High permeability
No night time Tx
Can perform anywhere
Ambulatory
Anywhere
4 - 5 Exchanges
Shorter Dwells
Dry night
Low transporter will have poor clearance
Exchange burden
IP Pressure with large volumes