Dialysis Flashcards
Indication for Renal Replacement
To treat acute or chronic loss in kidney function
- Remove waste and replenish lost fluids, move body fluid composition to normal
Kinds of Renal Replacement
Kidney Transplant
Dialysis
- Hemodialysis
- Peritoneal Dialysis
What is Dialysis
Remove excess fluids and waste products from the blood in place of the kidneys
- Not a cure, just treats the symptoms
Relies on the principles of diffusion, ultrafiltration, convection
Diffusion
Concentration gradient
- High to Low
Ultrafiltration
Fluid Pressure Gradient
- High to Low
Excess volume of fluid is cleared from the body using a pressure gradient between the blood and dialysate
Volume based
Convection
Fluid Pressure Gradient
- High to Low
Larger solutes are dissolved in fluid and are cleared from the body
Size based
Hemodialysis
Relies on Diffusion and Ultrafiltration
Peritoneal Dialysis
Relies on Diffusion, Ultrafiltration, and Convection
Concept of Dialysis
Blood runs parallel to a Dialysate, separated by a semipermeable membrane
- Fluid and solute move from the blood into the Dialysate
Dialysis
- What affects the rate of movement of solute
- Concentration gradient
- Permeability of membrane
- Surface area of membrane
- Length of time the blood is in contact with the membrane
Indication for Dialysis
- AKI
A: Acid Base Disturbances
E: Electrolyte Imbalances
I: Intoxication
O: Fluid Overload
U: Uremia
Indication for Dialysis
- CKD
Based on clinical status, initiate if one of the following is present
- Signs of kidney failure (acid-base, pruritus, serositis)
- Anuria
- Inability to control volume status or BP
- Deterioration in nutritional status
- Cognitive impairment
Dialysis
- Planning
Greater than 10% risk of Kidney Failure should be started on Dialysis Planning
OR
If patient is in CKD stage 4
Hemodialysis
- Components
- Dialyzer
- Dialysate
- Vascular Access
- Dialysis Machine
Hemodialysis
- Concept
Dialysis machine pumps blood into a dialyzer where it runs parallel to a dialysate
- Dialyzer contains the semipermeable membrane and acts as the kidneys
- Blood and Dialyzer are ran in a counter-current to increase concentration gradient
- Substances removed through diffusion
- Excess Water in plasma is removed through ultrafiltration
Patient requires heparin (anticoagulant) to prevent clotting
Hemodialysis
- Dialyzer with larger pores
- Dialyzer that is more permeable to water transport
Larger pores allow movement of more solutes
More permeable will result in greater ultrafiltration of water
Hemodialysis
- Diasylate
Cleansing liquid that contains electrolytes, purified water, dextrose
- Can add low amounts of potassium to treat hypokalemia
- Can add bicarbonate to treat metabolic acidosis
Vascular Access
Temporary Access
- Insertion of a venous catheter in large vein, not used for ongoing dialysis
Advanced Planning: Permeant Access
- Arteriovenous Fistula
- Arteriovenous Graft
Arteriovenous Fistula
Surgically connecting the radial artery to cephalic vein
- Takes 1-2 months of maturation before dialysis can be done
Preferred method
- Longest survival times
- Lowest rate of complications
Arteriovenous Graft
Insertion of a graft to connect branchial artery and basilic vein
- Takes 2-3 weeks of healing before dialysis can be done
Not preferred
- Shorter survival times
- Higher rate of complications
Function of a Dialysis Machine
- Measures dry weight (weight after removal of excess fluids) and BP
- Controls rate of blood flow and dialysate
- Controls ultrafiltration
Hemodialysis
- Complications
- Hypotension (20-30%)
- Hypertension (5-15%)
- Nausea/Vomiting
- Cramping
- Infection at access sites
- Worsening of Anemia
- AV Fistula/Graft/Catheter thrombosis
Hemodialysis
- Advantages
High solute clearance, allows for intermittent treatment
- 3x a week
Easier to detect under adequacy
Low rate of technique failure
Hemodialysis
- Disadvantages
Decline of residual kidney function
Takes a while for patient to adjust, will experience muscle cramps, disequilibrium, hypotension
Risk of infection
Incenter dialysis removes independence from patient
Peritoneal Dialysis
- Concept
Utilizes the highly vascularized abdominal viscera as a semipermeable membrane
- Dialysate is inserted through a catheter into the peritoneal cavity
- Solutes are removed from blood through the peritoneal membrane through diffusion and ultrafiltration
- Excess water is removed by ultrafiltraiton
Peritoneal Dialysis
- Contraindications
Absolute:
- Peritoneal adhesions from previous surgery
Relative:
- Ostomy
- Physical/Mental disability (Treatment requires independence and self monitoring)
- IBD
- Lack of care giver or inadequate home living conditions
Peritoneal Dialysate
- Components
- Uses lactate instead of bicarbonate
- Uses dextrose as osmotic agent
–> Changing concentration of dextrose will affect the amount of fluid removed - Electrolyte and Serum concentrations are similar
Peritoneal Dialysate
- Exchange
One cycle of
- Filling: Dialysate enters peritoneal cavity
- Dwelling: Solution remains in peritoneal
- Draining: Effluent fluid is removed from peritoneal cavity
Peritoneal Dialysate
- Administration
Has to be done at minimum daily
Peritoneal Dialysate
- Complications
- Peritonitis
- Exit site infection at catheter
- Absorption of glucose (hypertriglyceridemia or weight gain)
- Loss of albumin
Peritoneal Dialysate
- Advantages
- Hemodynamic stable due to slow ultrafiltration rate
- Higher clearance of larger solutes
- Preserves kidney function
- Sense of independence
Peritoneal Dialysate
- Disadvantages
- Protein and amino acid loss leading to malnutrition
- Glucose absorption
- Risk of peritonitis
- Hard to determine adequacy
Dialysis and Mortality
Mortality rates are still high even with dialysis
Dialysis vs Health Individuals
- Dialysis patients all have lower life expectancy
Dialysis and Cause of death
Most likely cause of death is Cardiovascular Related
Second most likely is infection
High vs Low Dialyzability
High = Lots of drug is removed
Low = Less of drug is removed
Factors affecting Dialyzability
- Molecular Weight
- Degree of protein binding
- Volume of distribution
- Water solubility
- Dialysis membrane
- Blood/Dialysate flow rate
Drug Dosing in Dialysis
- Renally Cleared Drugs
Need to have dose adjusted
- Kidneys not working, will not clear drugs like normal
Drug Dosing in Dialysis
- Highly Dialyzed Drugs
Need to have dose adjusted
- Adjust dose timings
Drug Dosing in Dialysis
- Unaffected by Renal Impairment Drugs
If more than 50% of drug is cleared by non-renal routes then no dose change is needed
Drug Dosing in Dialysis
- Toxic/Excreted in Active Form
Need to change dose or frequency to prevent accumulation
Hemodialysis vs Perinoteal
Hemodialysis
- Blood leaves the body and is fed into a dialysate, clean blood then enters back into the body
Peritoneal
- Blood does not leave the body, dialysate leaves body with waste
