Dialysis

Question 1

When is dialysis initiated in patients with chronic kidney disease?

Answer 1

In patients that are classified as having end stage renal disease, which is an average GFR of 7mL/min, but can be classed as 15mL/min or less.
Patients are usually initiated when other interventions are no longer working to provide symptom control.

Question 2

What are some of the symptoms a patient with end stage renal disease may present with?

Answer 2

Pruitis (Hyperphosphatemia)
Nausea and vomiting
Lethargy and fatigue (renal anaemia)
Drowsiness
Bone pain (hypocalcaemia)
Inability to urinate (inability of the kidneys to produce filtrate)
Weight loss

Question 3

What considerations should be made before initiating a patient on dialysis?

Answer 3

The commitment of the patient to attend dialysis appointments
Impact of dialysis on your daily routine, most patients feel better after receiving dialysis due to the removal of fluid and waste products however some can feel quite tired
The quality of life for a patient on dialysis vs the increased life expectancy (for elderly patients in particular is this worth it)

Question 4

What is the life expectancy for a patient on dialysis?

Answer 4

Average life expectancy on dialysis is 5-10 years, but some patients have lived well on dialysis for 20 or 30 years. This is often dependent on the age of the patient however as, patient’s initiated on dialysis over 75 may only live 2 or 3 years.

Question 5

Explain the main principles of dialysis.

Answer 5

Ultimately dialysis mimics the two functions of the glomerulus filtering waste and fluid from the blood and reabsorbing essential nutrients and minerals in the bloodstream.

Dialysis mimics the ultrafiltration mechanism of the glomerulus, removing fluid and waste products.
Fluid is removed by dialysis either by creating a hydrostatic or an osmotic gradient. Waste removal is facilitated in dialysis by diffusion across a semi-permeable membrane.

To ensure reabsorption of essential nutrients and minerals, the dialysate fluid composition can be tailored biochemistry of the patient to ensure it is comparable to the fluid running across the blood supply.

Question 6

Explain the concept of haemodialysis.

Answer 6

In haemodialysis an incision is made in your arm near the wrist connected to a tube which unfiltered blood from an artery flows within to an artificial kidney. This artificial kidney which is also known a dialyser is composed of a tube container lots of hollow fibres which create a semi permeable membrane (allowing waste diffusion) and also a pump which creates a hydrostatic pressure (for fluid removal). There is a counter current within the dialyser to bathe the blood and maximise the concentration gradients. The filtered blood having passed through the dialyser is then returned to the body via a vein on an incision made further up the armWhat . Dialysate fluid is then discarded.

Question 7

What pre-medication is given before haemodialysis?

Answer 7

Patient is anti-coagulated to prevent the blood from attempting to coagulate and causing blockage in one of the tubes.

Question 8

Explain the concept of peritoneal dialysis.

Answer 8

Peritoneal dialysis involves using the patient’s own peritoneum membrane which has a rich blood supply and lines the internal organs. In dialysis this mimics the glomerulus basement membrane. Usually the peritoneal space has very little fluid in it. The peritoneal space is filled with dialysate fluid via gravity. Usually a high glucose fluid is used to encourage fluid to be removed by osmosis into the dialysate fluid. Dialysate and waste products is drained from the peritoneal space via gravity into a drainage bag

Question 9

When are temporary catheters used for dialysis?

Answer 9

Often in emergent access however not used routinely due to increased risk of infection and thrombosis.

Question 10

What is the ‘gold standard’ for dialysis access and the purpose of the procedure?

Answer 10

Creation of a arteriovenous fistula, which is usually done 6-8 weeks before the initiation of dialysis under local or general anaesthetic.

This involves joining a thick walled artery (high pressure) to a thin walled vein (low pressure) usually in the arm.

Over the 6-8 weeks before initiation of dialysis, this joint matures which results in the enlargement and thickening of the vein. This provides two entry points for dialysis with a good blood flow/supply.

Question 11

What are the advantages and main counselling points for arteriovenous fistulas?

Answer 11

Reduced risk of thrombosis or infection in comparison to the temporary catheter however due to the presence of now two bulging vessel which you do not wanted to injure between dialysis sessions advise the patients to keep the area of the arm clean, covered and attempt to reduce contact with that area.

Question 12

What is dialysis adequacy?

Answer 12

This is a measure of essentially the effectiveness of the dialysis sessions by assessment of how well the toxins/waste is removed from the blood.

Question 13

How can the dialysis adequacy be enhanced?

Answer 13

Increasing the blood flow rate
Increasing the size or surface of the dialyser
Increasing the length of dialysis sessions or
Increasing the frequency of dialysis sessions

Question 14

However what are the limiting factors for optimising dialysis adequacy?

Answer 14

Must ensure the safety and the wellbeing of the patient at all times.
This includes:
- Measuring the weight of the patient before and after dialysis sessions to ensure not too much fluid is removed at once, this can lead to dizziness and hypotension.
- Gradually increasing the length of the dialysis sessions to prevent disequilibrium syndrome - headaches, nausea and vomiting, convulsions

Question 15

What causes convulsions associated with disequilibrium syndrome?

Answer 15

If a patient has a large concentration of urea removed, due to urea taking 12-24 hours to equilibrate in the blood and therefore during rapid haemodialysis this can cause imbalances precipitating symptoms.

Question 16

When is disequilibrium syndrome most likely to occur in dialysis patients?

Answer 16

Soon after initiation of dialysis or after missing consecutive dialysis sessions.

Question 17

What is the ideal length and frequency of haemodialysis?

Answer 17

4 hour sessions, three times a week

Question 18

What counselling points should be provided to patients for between sessions?

Answer 18

Counselling patients about fluid accumulation. All patients should have a tailored dry weight to aim, patient should not be gaining more than 1.5kg than this dry weight.

Question 19

What are patients at risk of if they exceed 1.5kg of their optimal dry weight?

Answer 19

Increased risk of pulmonary oedema and hospital admission for cardiac failure.

Question 20

What is the frequency of peritoneal dialysis?

Answer 20

Usually four times a day

Question 21

What is the advantages of peritoneal dialysis?

Answer 21

It can be completed at home which gives patients more freedom once they have been taught the aseptic technique of changing lines and bags.
Will receive a months supply at home.

Question 22

How is access for peritoneal dialysis achieved?

Answer 22

A Tencknoff (curly) catheter is inserted under general or local anaesthetic. It is inserted under the umbilicus and tunnelled through the abdominal wall. The curly end of the catheter sits in the peritoneal space to deliver the dialysate fluid.
Cuffs are stitched on either side of the abdominal wall to hold it in place, scar tissue over a couple of weeks will form, making it water tight.

Question 23

What medication will the patient when undergoing catheter insertion?

Answer 23

Prophylactic antibiotic

Question 24

What is the difference between continuous ambulatory peritoneal dialysis and automated peritoneal dialysis?

Answer 24

Continuous ambulatory peritoneal dialysis, as previously mentioned is the four times daily regimen.

Automated peritoneal dialysis is when the exchange is carried out over night usually via a machine of 8-10 hours.
This involves 1-3L of fluid dwelling in the peritoneal membrane for 1-3 hours at a time.

Question 25

What is the advantage of using automated peritoneal dialysis?

Answer 25

Improves the dialysis adequacy as there is more frequent and shorter dwell times so the fluid refreshes more frequently.

Question 26

What are the advantages of peritoneal dialysis?

Answer 26

It is less aggressive compared to haemodialysis, less fatigued
Diet and fluid restrictions less strict
Better cardiac stability due to gentler rate of fluid removal and disequilibrium?*
It can be completed at home , more independence
There is reduced anaemia as there is less access of needle sites

Question 27

What are the disadvantages of peritoneal dialysis?

Answer 27

Risk of PD peritonitis
Membrane can become fibrosed and inefficient
Risk of hypoglycaemia due to high glucose content solutions
Requires equipment and good technique, high responsibility of the patient
Less clearance of smaller molecules such as urea and creatinine compared to haemodialysis

Question 28

How is PD peritonitis detected?

Answer 28

Drainage bag changes from clear to cloudy, it is then sent to the lab. Must be treated appropriately as it can lead to loss of the catheter.

Question 29

What is the treatment regimen for peritonitis?

Answer 29

IV Vancomycin (can be given via the port so it can sit in the membrane) and PO Ciprofloxacin

Question 30

Why is PO Ciprofloxacin given?

Answer 30

Same bioavailability as IV (reduced further infection risk also*)

Question 31

What is the consequence of repeated peritonitis?

Answer 31

Membrane can become fibrosed

Question 32

What are some of the dietary recommendations for patient’s on dialysis?

Answer 32

Healthy diet - low fat and salt and high fibre
Low potassium
Low phosphate
High protein required in continuous ambulatory peritoneal dialysis

Having low phosphate is counter productive as phosphate is within protein and you are recommended to have protein in CAPD as it is loss during the process

Question 33

In which foods is potassium found?

Answer 33

In foods such as carbs, caffeine, chocolate. The most appropriate time for patients to have these is just before dialysis as it will then be filtered out.

Question 34

What is the fluid restriction for haemodialysis and peritoneal dialysis?

Answer 34

Haemodialysis: Urine output + 500mL/day
Peritoneal dialysis: Urine output + 750mL/day

Fluid counts as anything that is liquid at room temperature.
Sucking ice cubes can overcome thirst quenching.

Question 35

How might fluid management change for CKD patients once dialysis is initiated?

Answer 35

Usually stop diuretics unless residual function to pass urine

Question 36

How might acid/base management change for CKD patients once dialysis is initiated?

Answer 36

Stop sodium bicarbonate
Dialysis takes over this function

Question 37

How might hypertension management change for CKD patients once dialysis is initiated?

Answer 37

This is usually continue during dialysis, however it is important that due to fluid removal during dialysis the pre and post bp is monitored, bp usually drops after dialysis

Question 38

How might renal bone disease management change for CKD patients once dialysis is initiated?

Answer 38

Treatment remains the same

Question 39

How might erythropoietin management change for CKD patients once dialysis is initiated?

Answer 39

Risk of blood loss is increased on dialysis so is still required, usually given with IV iron in the clinic.

Question 40

How does dialysis affect the drugs?

Answer 40

As dialysis is mimicking the kidney it therefore to an extent affects how drugs are cleared from the body

Question 41

What is some of the drug factors that determine if the drug is removed from the body during dialysis?

Answer 41

Drugs that can increased likelihood of removal:
Drugs with a low molecular weight - Metronidazole (71), Gentamicin (543) partial and Vancomycin (1448) not at all

Drugs that usually have a high renal clearance
Drugs that have low plasma binding
Drugs with a high water solubility
Drugs with a low volume of distribution

Question 42

What is some of the dialysis factors that determine if the drug is removed from the body during dialysis?

Answer 42

The membrane type
The dialysis duration
The fluid composition both the volume and concentration
The peritoneum pathology - more fibrosed, less effective at removal
Blood flow rate

Question 43

What resources should you use for dosing in dialysis patients?

Answer 43

Renal drug handbook or the renal drug database for the online version