Dialysis Flashcards by Kevin Tea

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

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Kinds of Renal Replacement

Kidney Transplant

Dialysis
- Hemodialysis
- Peritoneal Dialysis

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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

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Diffusion

Concentration gradient
- High to Low

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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

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Convection

Fluid Pressure Gradient
- High to Low

Larger solutes are dissolved in fluid and are cleared from the body

Size based

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Hemodialysis

Relies on Diffusion and Ultrafiltration

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Peritoneal Dialysis

Relies on Diffusion, Ultrafiltration, and Convection

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Concept of Dialysis

Blood runs parallel to a Dialysate, separated by a semipermeable membrane
- Fluid and solute move from the blood into the Dialysate

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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

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Indication for Dialysis
- AKI

A: Acid Base Disturbances
E: Electrolyte Imbalances
I: Intoxication
O: Fluid Overload
U: Uremia

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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

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Dialysis
- Planning

Greater than 10% risk of Kidney Failure should be started on Dialysis Planning
OR
If patient is in CKD stage 4

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Hemodialysis
- Components

Dialyzer
Dialysate
Vascular Access
Dialysis Machine

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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

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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

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Hemodialysis
- Diasylate

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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

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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

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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

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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

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Measures dry weight (weight after removal of excess fluids) and BP
Controls rate of blood flow and dialysate
Controls ultrafiltration

Hemodialysis
- Complications

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Hypotension (20-30%)
Hypertension (5-15%)
Nausea/Vomiting
Cramping
Infection at access sites
Worsening of Anemia
AV Fistula/Graft/Catheter thrombosis

Hemodialysis
- Advantages

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High solute clearance, allows for intermittent treatment
- 3x a week

Easier to detect under adequacy

Low rate of technique failure

Hemodialysis
- Disadvantages

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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

Dialysis Flashcards

(41 cards)