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Year 3 - Kinetics > 5 - Peritoneal Dialysis > Flashcards

5 - Peritoneal Dialysis Flashcards

1
Q

What are the treatments for end-stage renal disease?

A
  • Renal replacement therapy (dialysis)

- Renal transplantation

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2
Q

What is the peritoneum?

A
  • Semi-permeable membrane lining peritoneal cavity

- Acts as “dialyzer”

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3
Q

How does peritoneal dialysis work?

A

Transport of solutes/water across the membrane separating 2 fluid-containing compartments (blood in peritoneal capillaries and dialysis solution in peritoneal cavity)

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4
Q

What is found in the dialysate solution and why?

A
  • Dextrose

- Higher concentrations of dextrose increase amount of fluid removed and enhances solute removal

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5
Q

What are some advantages of PD?

A
  • Done at home vs. in hospital or health centre
  • Travel/vacation is more feasible (portable)
  • Less impact on work life
  • Better for px requiring hemodynamic stability
  • Less blood loss
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6
Q

What are some disadvantages of PD?

A
  • Need adequate storage space at home
  • Need family support (risk of pt burnout)
  • Risk of peritonitis
  • Catheter malfunction, exit site and tunnel infections (many px require chronic laxatives to prevent catheter blocks)
  • Glucose exposure (reduced appetite, hyperglycemia, weight gain)
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7
Q

Describe the peritoneal dialysis procedure

A

Dialysis solution placed to dwell in peritoneal cavity for some period, then spent dialysate is removed and process is repeated

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8
Q

How is the osmotic gradient across peritoneum increased (increased solute removal)?

A
  • Increasing number of exchanges per day
  • Increasing volume of each exchange
  • Higher dialysate dextrose [ ]
  • Increase in dwell time
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9
Q

Describe CAPD

A
  • Continuous ambulatory PD
  • 4-5 exchanges (1.5-3 L each) per day
  • Manually (done by gravity)
  • Usual dwell = 4-6 h
  • Long night dwell (> 6 h)
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10
Q

Describe CCPD

A
  • Type of automated PD

- Continuous cycling PD (night cycler w/ day dwell)

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11
Q

Describe IPD

A
  • Type of automated PD

- Intermittent PD (night cycler w/ no day dwell)

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12
Q

Is there higher antibiotic clearances by CAPD or APD?

A

APD

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13
Q

How long does CAPD normally take?

A
  • 10-20 min for 2 L to flow into peritoneal cavity

- 10 min if 200 mL/min to drain the peritoneal cavity

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14
Q

Describe ultrafiltration

A

Water moves from area of low solute conc to high solute conc via osmotic gradient between relatively hypertonic dialysis solution and relatively hypotonic peritoneal capillary blood

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15
Q

Describe the 3 pore model in PD

A
  • Transcellular pore (< 0.8 nm) – transfers water
  • Small pore (< 4-6 nm) – 99% of all pores; transfers small solutes like urea, creatinine, and potassium
  • Large pore (> 20 nm)
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16
Q

In PD, drug removal occurs by _____

A

Diffusion

17
Q

What are the 2 directions of drug movement in PD?

A
  • Blood to dialysate

- Dialysate to blood (after IP administration)

18
Q

What factors affect movement of drugs from blood into dialysate?

A
  • Molecular weight (smaller molecules < 1000 daltons pass more easily through peritoneal membrane)
  • Protein binding (low plasma protein binding < 50% will be able to pass into dialysate when given systemically)
  • Vd (small Vd < 1 L/kg are water soluble so mostly exist in body water and circulatory system, so can pass into dialysate)
  • PD fluid flow rates
  • Peritoneal membrane solute transport status
  • Residual renal function
19
Q

What affect do PD fluid flow rates have on movement of drugs from blood into dialysate?

A
  • Factors = volume of fill per exchange and frequency of dialysate exchanges
  • Greater drug movement from blood to dialysate w/ large volumes, frequent exchanges, and long dwell time (facilitates removal of large drugs)
20
Q

For peritoneal clearance to be clinically important, its value should be at least __% of total body clearance

A

20%

21
Q

Drug clearance by CAPD cannot exceed _____

A

Dialysate outflow

22
Q

What is the equation for Cl PD?

A

Dialysate outflow rate (total volume per day in L/ 24 h) * fraction unbound

23
Q

What is the equation for Cl ESRD?

A

Ke ESRD * Vd

24
Q

What is the equation for Cl total?

A

Cl ESRD + Cl PD

25
Q

How can you calculate the estimated half life for a pt based on their PD regimen?

A
  • Calculate Cl PD and Cl ESRD
  • Calculate total PD
  • Calculate ke from Cl total / Vd, then convert to t1/2
26
Q

What is examined in a peritoneal equilibration test (PET)?

A

Relative passage of creatinine and glucose across peritoneal membrane

27
Q

What effect does peritonitis have on movement of drugs across peritoneal membrane?

A
  • Enhances movement of drugs (inflammation increased diffusion)
  • Enhances movement from blood to dialysate and from dialysate to blood
28
Q

Urine output of ____ mL per day or more is considered significant for antibiotics

A

100 mL

29
Q

What factors affect movement of drugs from dialysate to blood?

A
  • Vd (large Vd will have faster movement)
  • MW
  • Type of PD (APD will have higher flow rates and greater clearance)
  • Peritonitis
30
Q

How do you calculate PD clearance for a drug administered IP?

A

Cl PD = (C dialysis * V dialysis) / (C serum * T dialysis)

  • C dialysis = drug conc in dialysate effluent
  • V dialysis = volume of dialysate effluent
  • C serum = serum drug conc at midpoint of dwell
  • T dialysis = duration of drug dwell
31
Q

How do you calculate the predicted steady state serum peak level on a PD regimen?

A
  • Calculate Cl total
  • Calculate ke (Cl total / Vd)
  • Use equation Cpss = [F IP * D] / [Vd * 1-e^-ke*T]
  • F IP = IP bioavailability
32
Q

How do you calculate the predicted steady state serum trough level on a PD regimen?

A

Ctss = Cpss * e^-ke*T

Year 3 - Kinetics (12 decks)

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