Peritoneal Dialysis PD

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Peritoneal Dialysis (PD)

• Principles
• Peritoneum
• Fluid and Solute Removal
• PD Fluid
• Treatment modes CAPD/APD
• Complications
• Treatment Strategy

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Principles of PD

• Dialysis fluid is introduced to the peritoneal
  cavity through a catheter placed in the lower
  part of the abdomen.
• A thin membrane, called the peritoneum, lines the
  walls of the peritoneal cavity and covers all the
  organs contained in it.
• In PD the peritoneum serves as the dialysis
  membrane. The peritoneal cavity can often hold
  more then 3 litres, but in clinical practice only
  1.5 2.5L of fluid are used.
• This is an intra-corporeal blood purification as
  no blood ever leaves the body of the patient.

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Principles of PD

• The abdominal cavity, hold the large organs of
  the digestive system, is lined by the peritoneum.
• In PD, special fluid is instilled through a
  permanent catheter in the lower abdomen.

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Principles of PD

• An osmotic pressure gradient is applied by the
  addition to the dialysis fluid of an osmotic
  agent which will suck fluid from the blood.
• The concentration of this osmotic agent is chosen
  to give just the fluid removal needed. In most
  cases glucose is used to create the osmotic
  pressure.
• Fluid is removed by ultrafiltration driven by an
  osmotic pressure gradient. (Eg. Yellow/Green/Red
  Bags)

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Principles of PD

• Solutes are transported across the membrane by
  diffusion.
• The driving force is the concentration gradient
  between the PD fluid and the blood.
• Waste products present in the blood per fusing
  the peritoneum will diffuse from the blood
  vessels into the cleaner dialysis fluid.

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Principles of PD

• The dialysis fluid should be instilled for 4 to 6
  hours.
• When the dialysis fluid is drained from the
  abdominal cavity, it contains waste products and
  excess fluid extracted from the blood.
• PD is most often applied and effective as a
  continuous therapy. In this way it is a more
  physiological treatment then Haemodialysis (HD)

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Principles PD / HD
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The Peritoneum
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The Peritoneum

• The abdominal cavity and all the organs contained
  in it are lined by a thin smooth membrane, the
  peritoneum.
• It is a loose connective tissue containing blood
  vessels and nerves.
• If put under the microscope, three layers can be
  identified between the peritoneal cavity and the
  blood stream.
• The capillary wall / the interstitium / the
  mesothelium
• Each of these is a barrier to the transport of
  fluid and solutes.

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Fluid Removal

• To understand how fluid removal is achieved, we
  need to understand how osmosis works.
• Osmosis is the process in which water moves
  through a semi permeable membrane from an area of
  high water concentration (ie low solute
  concentration) to an area of low water
  concentration (ie higher solute concentration).

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Fluid Removal

• The osmotic agent normally used in PD fluid is
  glucose.
• Not an ideal osmotic agent, as it is readily
  transported across the peritoneum.
• Large concentration glucose creates a temporary
  osmotic gradient before being adsorbed into the
  blood.
• The higher the glucose concentration, the larger
  the osmotic pressure, resulting in a larger fluid
  removal.
• If PD exchanges are missed or dwell more than 6-8
  hours, fluid may be gained by the patient rather
  then lost.
• The Volume of dialysis solution administered is
  also important for the total fluid removal, as it
  will take longer for the concentration gradient
  to decline in a large volume of fluid.

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Fluid Removal

• Transport capacity for the fluid across the
  Peritoneal membrane varies greatly between
  patients.
• Mainly the pore area and the capacity to reabsorb
  fluid which affect fluid removal

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Solute Removal

• The most important principle for solute removal
  in PD is diffusion, for which the driving force
  is the concentration gradient between the blood
  and the dialysis fluid.
• Small solutes move quickly through the membrane
  creating an equilibrium during the dwell period.
• Larger solutes move slowly across the peritoneum,
  reaching equilibrium point takes a long time.

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Fluid Removal

• SoBoth solute and fluid
  removal in PD is controlled by
• 1) glucose concentration
• 2) dwell time
• 3) volume
• 4) peritoneal membrane characteristics

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PD Fluid

• Components of PD fluid can be divided in into
  electrolytes, buffer and osmotic agents.
• The most abundant electrolyte in PD fluid is
  sodium. Its hyponatremic, so it has a
  concentration lower than blood to ensure
  sufficient removal of sodium.
• Standard PD fluid contains no potassium.
• Today, there is a tendency to use normcalcemic PD
  fluid as many patients receive extra calcium from
  phosphate-binding drugs.
• The buffer normally used in PD is lactate.
  Lactate is metabolised to form bicarbonate, the
  most important buffer in the blood.

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PD Fluid

• The major osmotic agent used today is glucose.
• As the rate of fluid transport is related to the
  osmotic strength of the PD solution, the
  ultrafiltration can be controlled by an
  appropriate glucose concentration. Normal range
  of concentrations include 1.5, 2.3 4.25.
• Glucose is not ideal, as it is rapidly absorbed
  from the PD fluid. This may lead to problems with
  fluid removal, patient gains calories and can
  lose there appetite. Resulting in overweight and
  malnourishment. Disturbances of the carbohydrate
  and lipid metabolism may also occur.
• Research to find alternative osmotic agents has
  resulted in new products which are still not
  widely used. Amino acids are an interesting
  alternative as they provide nutritional
  supplement.
• High molecular weight glucose polymer
  (extraneal/icodextrin) provide sustained
  ultrafiltration for long overnight dwells.

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Treatment Modes CAPD/APD

• Whatever method is used it is of the highest
  importance that the treatment is performed with
  great hygienic care as the introduction of
  bacteria in to the abdomen can lead to
  peritonitis.
• Continuous Ambulatory Peritoneal Dialysis, CAPD
  is most widely used know as the manual method
  where each exchange is taken care of by the
  patient.
• Typically regime 4 bags x 2L/day. This means that
  the patient performs 4 bags during the day.

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Treatment Modes CAPD/APD

• To increase the efficiency of PD and help the
  patient with the exchanges, a machine can be
  used, known as Automated Peritoneal Dialysis of
  APD.
• Advantages of APD v CAPD are 1) higher clearance
  of solutes, as higher volumes can be used 2)
  better fluid removal, as shorter dwell time can
  be used 3) more freedom during the daytime as no
  exchanges need to be made.
• Drawbacks of APD are that of a higher cost and
  portability.

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Complications

• The most common in PD and also one of the major
  problem with the therapy in general, is
  PERITONITIS.
• The normal cause of inflammation is bacterial
  infection. Bacteria from the patients skin,
  equipment or from an unclean environment can be
  flushed into the abdominal cavity by the
  instilled PD fluid.
• The exit site of the catheter is also an
  infection route. In rare cases bacteria may enter
  from the intestines.

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Complications

• During an episode of peritonitis many events take
  place in the affected tissue which may change the
  transport characteristics of the peritoneum (eg
  formation clots or adhesions)
• Repeated episodes eventually damage the
  peritoneum and force the patient to choose
  another treatment (HD).
• PD leaks, Hernias are another complications
  partly a result of the increased abdominal
  pressure. APD can be a suitable option (lying
  down) as these patients are not CAPD candidates
  with the added abdominal pressure.
• Patient technique survival is better for HD ie,
  patients can usually be treated with HD for a
  longer period of time.
• Reoccurring episodes of peritonitis together with
  loss of residual function are the major causes
  for patients transferred from PD to HD.

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Treatment Strategy

• Many factors are considered and assessed to
  ascertain the best effective treatment for each
  individual patient
• Personal needs and preferences are of great
  importance, to suit lifestyle.
• Some prefer nightly treatments and are
  comfortable operating a machine
• PD is often chosen as a temporary treatment of
  transplant candidates, waiting for a suitable
  kidney.
• PD is often the best choice for pediatric
  patients as the continued blood purification is
  probably the reason why children grow better than
  HD.
• Cardiovascular problems and blood access problems
  can be impossible to treat on HD PD is an
  alternative.
• The peritoneal membrane characteristics, ie. The
  transport properties of the peritoneum can vary
  widely among patients. A small person may have a
  large peritoneal surface area with many pores
  available for transport. However, a large person
  who needs much more dialysis, may have only a
  small peritoneum.

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Ged PD Coordinator

• Thanks for your time this morning and have a
  great day!!!!!

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Peritoneal Dialysis

• Information and pictures in this presentation has
  been collaborated in conjunction with
• Gambro BASICS
• Fresenius Medical Care
• Baxter Health Care

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