lec5 sem3 year2 RMWK3 2012 02 18

							                      Dialysis;
                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.)
                          Hemodialysis
•   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.
•




                          Hemodialysis
•   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
    patient.
              Types of vascular access
   •   ArterioVenous fistula
   •   Arteriovenous graft
   •   Central venous catheter



              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
Common:
  • 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 peritonitis)
   •    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
          or
   •   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
       dialysis

   •   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
Infectious:
   • exit-site inflammation (flare, suppurative secretion,
   granulation)
   • peritonitis (turbid dialysate, abdominal pain, fever)
Non-infectious:
   • 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
                               Summary;
advantages
    • maximum solute clearance
    • best tx for severe hyper-K+
    • ready availability
    • limited anti-coagulation time
    • bedside vascular access
disadvantages
    • hemodynamic instability
    • hypoxemia
    • rapid fluid + solute shifts
    • complex equipment
    • specialized personnel

                           Summary;
                       Peritoneal Dialysis
advantages

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