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                 types and importance
                     Learning Objectives
                        Dialysis; Definition
   •   Dialysis is an artificial procedure that is a substitute for many of the normal duties
       of the kidneys.
   •   Done by cleansing the blood/body fluids by passing it through a special machine.

                       Dialysis; Importance
   •   Dialysis is necessary when the kidneys are not able to filter the blood.
   •   Dialysis allows patients with kidney failure a chance to live productive lives.
   •   Occasionally used for some forms of poisoning

                       Dialysis; Limitations
   •   Dialysis is an imperfect treatment to replace kidney function because it does not
       correct the endocrine functions of the kidney.

                            Types of dialysis
There are three primary types of dialysis:
   • hemodialysis
   • peritoneal dialysis,
   • hemofiltration
                      Principles of dialysis
   •   Dialysis works on the principles of the diffusion of solutes and ultrafiltration of
       fluid across a semi-permeable membrane.
   •   Blood flows by one side of a semi-permeable membrane, and a dialysate, or
       special dialysis fluid, flows by the opposite side. A semipermeable membrane is a
       thin layer of material that contains various sized holes, or pores.
   •    Smaller solutes and fluid pass through the membrane, but the membrane blocks
       the passage of larger substances(proteins, RBCs etc.)

   •   In hemodialysis, a patient's blood is pumped into a dialyzer containing two fluid
       compartments configured as bundles of hollow fiber capillary tubes or as parallel,
       sandwiched sheets of semipermeable membranes.
•    Blood in the first compartment is pumped along one side of semipermeable
    membrane while a crystalloid solution (dialysate) is pumped along other side, in a
    separate compartment, in opposite direction.

•   Concentration gradients of solute b/w blood& dialysate lead to desired changes in
    patient's serum solutes, such as a reduction in urea nitrogen and creatinine; an
    increase in HCO3; and equilibration of Na, Cl, K, and Mg.
•    The dialysate compartment is under negative pressure relative to the blood
    compartment to prevent filtration of dialysate into the bloodstream and to remove
    the excess fluid from the patient. The dialyzed blood is then returned to the
           Types of vascular access
•   ArterioVenous fistula
•   Arteriovenous graft
•   Central venous catheters

           Indications of hemodialysis
•   . Renal insufficiency or failure (acute or chronic) with any of the following that
    cannot otherwise be controlled:
•   Fluid overload
•   Hyperkalemia
•   Hypercalcemia
•   Metabolic acidosis
•   Pericarditis
•   Uremic symptoms
•   GFR < 10 mL/min/1.73 m2 BSA (chronic renal failure, no diabetes)
•   GFR < 15 mL/min/1.73 m2 BSA (chronic renal failure, diabetes)
•   Some poisoning

    Contraindications for hemodialysis
•   Uncooperative or
•   Hemodynamically unstable patient
           Complications during dialysis
   • Hypotension (20-50%)
   • Muscle cramps (5-20%)
   • Nausea (5-15%)
   • Headache (5%)
   • Itching (5%)
   • Chest pain/back pain (2-5%)
   • Fever and chills (<1%)
Less common but serious
   • Dialysis disequilibrium
   • Arrhythmias
   • Cardiac tamponade
   • Intracranial bleeding
   • Hemolysis
   • Air embolism
                        Peritoneal dialysis
   •   Complementary to hemodialysis
   •   Peritoneal dialysis uses the peritoneum as a natural permeable membrane through
       which water and solutes can equilibrate.
   •   Peritoneal dialysis is less physiologically stressful than hemodialysis, does not
       require vascular access, can be performed at home, and allows patients much
       greater flexibility
           Peritoneal dialysis; indications
   •   Peritoneum (capillary endothelium, matrix, mesothelium) = semipermeable
       dialysis membrane through which fluid and solute move from blood to dialysis
       solution via diffusion and convection
   •   Effective peritoneal surface area = perfused capillaries closed to peritoneum (↓ in
   •   Ultrafiltration (movement of water) enabled by osmotic gradient generated by
       glucose or glucose polymers(isodextrin)

       Peritoneal dialysis; Contraindications
   •   Implanted via laparoscopy, punction or laparotomy (total     anesthesy)
   •    PD is started 3 weeks following the impantation of catheter

Peritoneal dialysis; indications

   •   Same indications as for hemodialysis (except for poisonings) in patients who:
   •   Have inadequate vascular access
   •   Prefer self-therapy
Peritoneal dialysis; Contraindications
   • Absolute: Loss of peritoneal function or adhesions that limit dialysate flow, recent
       abdominal wounds, abdominal fistulas, abdominal wall defects that prevent
       effective dialysis or increase infection risk (eg, irreparable inguinal or
       diaphragmatic hernia, bladder extrophy), patient's condition not amenable to

   •   Relative: Abdominal wall infection, frequent episodes of diverticulitis, inability to
       tolerate large volumes of peritoneal dialysate, inflammatory bowel disease,
       ischemic colitis, morbid obesity, peritoneal leaks, severe undernutrition

Complications of Peritoneal dialysis
   • exit-site inflammation (flare, suppurative secretion,
   • peritonitis (turbid dialysate, abdominal pain, fever)
   • hernias
   • Hydrothorax
   • Leakage of dialysate along the peritoneal catheter
   • Drainage failure of dialysate (dislocation or catheter obstruction by fibrin)
   • Morphologic changes of peritoneum following long-lasting PD (peritoneal
       fibrisis, mesotelial damage, vasculopathy and neo-angiogenesis) leading to loss of
       UF capacity

   • maximum solute clearance
   • best tx for severe hyper-K+
   • ready availability
   • limited anti-coagulation time
    • bedside vascular access
    • hemodynamic instability
    • hypoxemia
    • rapid fluid + solute shifts
    • complex equipment
    • specialized personnel

                        Peritoneal Dialysis

• simple to set up and perform
• easy to use
• hemodynamic stability
• no anti-coagulation
• bedside peritoneal access
    • unreliable ultrafiltration
    • slow fluid + solute removal
    • drainage failure, leakage
    • catheter obstruction
    • respiratory compromise
    • hyperglycemia
    • peritonitis

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