Renal replacement therapy: dialysis

Question 1

Functions of the kidneys

Answer 1

Excretion of nitrogenous waste products

Maintenance of acid and electrolyte balance

Control of blood pressure

Drug metabolism and disposal

Activation of vitamin D

Production of erythropoietin

Question 2

When is renal replacement therapy usually indicated?

Answer 2

When eGFR <10 ml/min

Question 3

Types of renal replacement therapy (4)

Answer 3

Renal transplant

Haemodialysis

Peritoneal dialysis

Conservative Kidney Management

Question 4

Define dialysis

Answer 4

Dialysis is a process whereby the solute composition of a solution, A, is altered by exposing solution A to a second solution, B, through a semipermeable membrane.

Ie filtering the blood outwith the kidneys

Question 5

Principles of dialysis

Answer 5

Diffusion

Ultrafiltration

Question 6

What is required for dialysis to occur?

Answer 6

Semipermeable membrane => artifical kidney in haemodialysis or the peritoneal membrane in PD

Adequate blood exposure to the membrane => blood from outside the body in haemodialysis and the mesenteric circulation in Peritoneal dialysis

Dialysis Access => vascular in haemodialysis, peritoneal in PD

Anticoagulation in haemodialysis

Question 7

Difference between haemodialysis and peritoneal dialysis

Answer 7

In hemodialysis, blood is pumped out of your body to an artificial kidney machine, and returned to your body by tubes that connect you to the machine.

In peritoneal dialysis, the peritoneum acts as a natural filter.

Question 8

What are the permanent access points for haemodialysis?

Answer 8

Arteriovenous fistula - joining an artery and vein in your arm to make it stronger.

Question 9

What are the temporary access points for haemodialysis?

Answer 9

Tunneled venous catheter and non-tunneled venous catheter

Usually inserted into neck region

Question 10

What can pass freely across the membrane into the dialysate

Answer 10

Na+
K+
Ca2+
HCO3-

Question 11

What restrictions must dialysis patients implement?

Answer 11

Fluid

Dietary - K+, Na+ and phosphate

Question 12

What needs to be considered when working out fluid restrictions for dialysis patients?

Answer 12

Residual urine output - remaining in bladder

Interdialytic weight gain - excessive intake of fluids can cause weight gain - detrimental effects on survival/CVS/QOL

Question 13

Describe peritoneal dialysis

Answer 13

A balanced dialysis solution is instilled into the peritoneal cavity via a tunnelled, cuffed catheter, using the peritoneal mesothelium as a dialysis membrane

Catheter goes into your stomach

Question 14

What are the 2 types of peritoneal dialysis?

Answer 14

Continuous ambulatory peritoneal dialysis (CAPD) - blood is filtered several times during the day (you just connect yourself to the dialysis for a few hours and can sit and read etc)

Automated peritoneal dialysis (IPD) - filters your blood during the night as you sleep - done by machine

Question 15

2 types of haemodyalisis

Answer 15

Home haemodialysis

Satellite / hospital haemodialysis

Question 16

What is the most common osmotic agent for ultrafiltration of fluid in peritoneal dialysis

Answer 16

Glucose

Question 17

What is dwell time?

Answer 17

Dwell time = The time that the dialysis solution is in your belly.

In continuous dialysis you usually change the solution at least 4 times a day and sleep with solution in your belly at night - it absorbs waste and extra fluid in this time.

The fluid sits in the peritoneal cavity for several hours whilst waste products pass from the capillaries into the liquid. It is then drained out into an empty bag and thrown away. The process of adding fresh liquid and draining out used liquid is called a dialysis ‘session’ or ‘exchange’. It is usually performed four times a day, every day, and each session takes about 40 minutes.

Question 18

What is the dialysis solution made up of?

Answer 18

Water with salt and other electrolytes etc

Question 19

Complications associated with peritoneal dialysis

Answer 19

Exit site infection, tunnel infection

Tube malfunction, abdominal wall herniae

PD peritonitis

Ultrafiltration failure - blood isn’t cleaned

Encapsulating peritoneal sclerosis

Question 20

Which organisms are related to peritoneal dialysis peritonitis?

Answer 20

Gram +ve = skin contaminant

Gram -ve = bowel origin

Mixed = suspect complicated peritonitis e.g perforation

Question 21

What is Encapsulating peritoneal sclerosis?

Answer 21

Devastating but rare complication of long-termperitonealdialysis.

Extensive thickening and fibrosis of the peritoneum resulting in the formation of a fibrous cocoon encapsulatingthe bowel leading to intestinal obstruction.

Question 22

Indications for dialysis in end stage renal disease? (5)

Answer 22

Advanced uraemia (raised level of urea and other nitrogenous waste compounds in the blood)

GFR 5-10 ml/min

Severe acidosis (bicarbonate <10 mmol/l)

Treatment resistant hyperkalaemia (K >6.5 mmol/l)

Treatment resistant fluid overload

Question 23

For haemodialysis patients what is their fluid intake usually restricted to?

Answer 23

500-800 ml/24 hours

which should = their urine output and insensible losses

Question 24

Complications of haemodialysis

Answer 24

Cardiovasular problems - Intra-dialytic hypotension and cramps, Arrythmias

Coagulation - Clotting of vascular access, Heparin related problems

Other - Allergic reactions to dialysers and tubing, Catastrophic dialysis accidents (rare)

Question 25

How is the choice of dialysis made?

Answer 25

Patient’s own choice = most important.

Education and shared decision making required

Question 26

What is Conservative kidney management?

Answer 26

Continued care without dialysis or a kidney transplant.

Supportive - symptomatic management, holistic MDT approach, anticipatory care planning