Clinical Monitoring Systems

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Principles of Peritoneal Dialysis
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Diffusion

• Transfer by diffusion is the passive transfer of
  solutes across the membrane, without the passage
  of solvent (water).

Blood
Membrane
Dialysate
1 - Red blood cell 2 - Bacteria
Beta 2-m (Solute PMgt5000)
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
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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.
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Ultrafiltration
CAPD
9
Ultrafiltration
10
Ultrafiltration
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Clearance Peritoneal Equilibration
Twardowski, University of Missouri
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(No Transcript)
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Process of PD

• Exchange
• Drain(lt20 Minutes)
• Fill(lt10 minutes)
• Dwell - (CAPD 4 - 8 hours)
• - (APD 30mins 2 hours)
• CAPD
• Manual
• Day Time Exchanges
• Procedure Every 4-8 Hours

14
Outline benefits of PD

• Medical
• 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

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Disadvantages

• Medical
• Risk of infection
• 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

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CAPD
Continuous Therapy
Volume
Benefits
Limitations
0
24
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
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APD
Intermittent Therapy
Volume
Benefits
Limitations
0
24
Time

• Optimum dialysis for High permeability
• No night time Tx
• Can perform anywhere

• Low transporter will have poor clearance
• Exchange burden
• IP Pressure with large volumes

Ambulatory Anywhere 4 - 5 Exchanges Shorter
Dwells Dry night