Dialysis Flashcards
What is dialysis?
A method for performing the filtration tasks of the kidney artificially – specifically removing waste products, salts and fluid from the blood
What are the two processes that dialysis rely on?
Diffusion
Ultrafiltration
What eGFR indicates dialysis?
eGFR is less than 10ml/min
When is acute dialysis indicated?
It is indicated in patients with severe acute kidney injury, in which the following complications arise…
Acidosis, in which bicarbonate levels fall below 10mmol/l
Electrolyte Imbalance, such as hyperkalaemia, where K > 6.5mmol/l
Intoxication, which is the overdose of certain medications
Oedema, specifically pulmonary
Uraemia Symptoms, such as seizures or reduced consciousness
When is dialysis indicated?
It is indicated in end stage renal failure and advanced chronic kidney disease– specifically stage four (GFR <30) and stage five (GFR < 15)
What are the two types of dialysis?
Haemodialysis
Peritoneal dialysis
What is haemodialysis?
It involves a haemodialysis machine filtering waste products, salts and fluid from the blood
In which two locations can haemodialysis be conducted?
Home
Satellite clinics
What is a typical haemodialysis regime?
Four hours a day for three days a week
In what two ways can blood supply be accessed for haemodialysis?
Arteriovenous (AV) Fistula
Tunnelled Cuffed Catheter
What is an AV fistula?
An an artificial connection between an artery and a vein
Why is an AV fistula preferred for haemodialysis?
It bypasses the capillary system and allows blood to flow under high pressure from the artery directly into the vein
This provides a permanent, large, easy access blood vessel with high pressure arterial blood flow
How is an AV fistula created?
Surgery
Why is an AV fistula not used for acute dialysis?
A maturation period between 6 weeks to 8 weeks is required before it can be used
Where are AV fistula normally formed?
Forearm
What are the three types of AV fistulas?
Radio-Cephalic Fistula
Brachio-Cephalic Fistula
Brachio-Basilic Fistula
What four abnormalities do we look for when examining an AV fistula?
Skin Integrity
Aneurysms
Palpable Thrill
“Machinery Murmur”
How do we avoid the complications associated with AV fistulas?
We prescribe patients anticoagulant agents whilst receiving treatment
Is blood taken from the fistula?
We never take blood from a fistula
This is a lifeline for the patient, providing access to dialysis
What is a tunnelled cuffed catheter?
A tube inserted in to the subclavian or jugular vein with a tip that sits in the superior vena cava or right atrium
It has two lumens, one where blood exists the body and one where blood enter the body
What is the permanent blood access point for haemodialysis?
AV fistula
What is the temporary blood access point for haemodialysis?
Tunnelled cuffed catheter
In diabetic patients, what do we need to remember about haemodialysis treatment?
It can result in falsely low HbA1c readings
What is peritoneal dialysis? What catheter is used?
It involves a dialysis solution, containing dextrose, entering the abdomen via a Tenchkoff catheter
This results in ultrafiltration from the blood, across the peritoneal membrane, into the dialysis solution
After a period of time, the dialysis solution is replaced, removing the waste products that have filtered out of the blood
Tenchkoff catheter
What process occurs in peritoneal dialysis?
Ultrafilration
What are the two main types of peritoneal dialysis?
Continuous Ambulatory Peritoneal Dialysis (CAPD)
Intermittent Peritoneal Dialysis (IPD)
What is CAPD?
It involves filling the abdomen with dialysate, allowing it to remain there for a prescribed period of time, then draining the fluid
What is the typical CAPD regimen?
Two litres of fluid being inserted into the peritoneum and changed four times daily
What is IPD?
It involves a machine performing multiple exchanges overnight whilst the patient sleeps
The machine automatically fills the abdomen with dialysate, allows it to remain there for a prescribed period of time and then drains it to a sterile bag that the patient empties in the morning
How long does IPD take?
Eight to ten hours
What dialysis requires diasylate?
Both haemodialysis and peritoneal dialysis
What is the sodium concentration in diasylate? What effect does this have?
High, which is the same concentration as sodium within the blood
This maintains sodium levels and results in no change.
What is the potassium concentration in diasylate? What effect does this have?
Low, which is a slightly lower concentration than potassium within the blood
This allows some potassium to move into the dialysate, preventing a rapid major drop in potassium – which could eventually result in arrythmias
What is the calcium concentration in diasylate? What effect does this have?
High, which is the same concentration as calcium within the blood
This maintains calcium levels and results in no change
What is the bicarbonate concentration in diasylate? What effect does this have?
High, which is a higher concentration than bicarbonate within the blood
This enables bicarbonate to move from the dialysate to move into the bloodstream, thus preventing acidosis
What is the creatinine concentration in diasylate? What effect does this have?
None
This means that most creatinine moves from the bloodstream into the dialysate to be filtered
What is the urea concentration in diasylate? What effect does this have?
None
This means that most urea moves from the bloodstream into the dialysate to be filtered
What are the two markers of dialysis efficiency?
Creatinine
Urea
What is the glucose concentration in diasylate? What effect does this have?
High, which is a higher concentration than glucose within the blood
This enables glucose to move from the dialysate to move into the bloodstream
What are the four complications of peritoneal dialysis?
Bacterial Peritonitis
Peritoneal Sclerosis
Ultrafiltration Failure
Weight Gain
What is bacterial peritonitis?
An infection of the peritoneum lining the abdomen
Why is bacterial peritonitis a complication of peritoneal dialysis?
This is due to the infusions of glucose solution into the peritoneum enabling bacterial growth
What organisms tend to cause bacterial peritoneal secondary to dialysis? Name an example
Coagulase negative staphylococcus
Staphylococcus epidermis
What is a clinical sign of bacterial peritonitis?
The drained dialysis fluid will appear cloudy instead of clear
This is due to the increased number of white cells
How do we treat bacterial peritonitis positive infections?
Vancomycin - until the causative agent is identified
How do we treat bacterial peritonitis negative infections?
Ciprofloxacin
When should we consider if the peritonitis is related to bowel perforation - instead of dialysis?
When the bacterial agent is mixed
What is peritoneal sclerosis?
It is thickening and scarring of the peritoneal membrane
What is the cause of peritoneal sclerosis?
Constant inflammation
What can peritoneal sclerosis lead to?
Bowel obstruction
What is ultrafiltration failure?
Ultrafiltration failure occurs when the patient starts to absorb the dextrose in the filtration solution
This reduces the filtration gradient making ultrafiltration less effective over time
How do we avoid the complication of ultrafiltration failure?
We don’t keep patients on peritoneal dialysis for more than two to three years
Why is weight gain a complication of peritoneal dialysis?
When dextrose within the dialysate is absorbed by the patient
When the patient intakes too much fluid
How do we avoid the complication of weight gain?
Fluid restriction
How do we determine a dialysis patient’s fluid restriction?
Residual urine output
The type of dialysis treatment
What is the fluid restriction of patients on haemodialysis?
500-800ml/ of fluid intake over a period of 24 hours.
What is the fluid restriction of patients on peritoneal dialysis?
These patients have a better urine output and therefore their fluid intake is less restricted
What is the fluid restriction for patients with a small urine output?
The smaller the urine output, the more severe and restrictive the fluid intake becomes
What is the fluid restriction for patients with a high urine output?
The greater the urine output, the less severe and restrictive the fluid intake becomes
How can we help patients who struggle to restrict their fluid intake?
We can remove any excess fluid during dialysis sessions
What is the maximum amount of fluid that should be removed per dialysis session?
3L
What are the five complications of haemodialysis?
Hypotension
Anaemia
Hyperkalaemia
Renal Bone Disease
Heart Failure
Why is hypotension a complication of haemodialysis?
In dialysis, the kidney function is improved and therefore patient’s blood pressure control becomes better
In cases where patients are on antihypertensives, hypotension may occur as a result
How do we prevent hypotension in haemodialysis?
We should review the patient’s medications before treatment commences
Why is anaemia a complication of haemodialysis?
Iron is removed by haemodialysis
Patients usually intake less iron due to diet restrictions
Failing kidneys reduce the production of erythropoietin
How do we prevent anaemia in haemodialysis patients?
We prescribe patients weekly erythropoietin injections alongside IV iron supplements
Why is hyperkalaemia a complication of haemodialysis?
Potassium is a mineral that is normally removed from the body by the kidneys
In cases where dialysis patients consume too much potassium, hyperkalaemia can occur
What potassium level results in arrhythmias?
> 6.5mmol/L
How do we prevent hyperkalaemia in haemodialysis patients?
Dialysis patients are advised to restrict their potassium intake
What is renal bone disease?
Renal bone disease occurs when damaged kidneys are no longer able to process vitamin D, which helps you absorb calcium
How do we prevent renal bone disease in haemodialysis patients?
We prescribe patients calcitriol, advise diet restrictions of phosphate and prescribe phosphate binders with meals – which prevents the absorption of phosphate from the diet
Why is heart failure a complication of haemodialysis?
It occurs when AV-fistulas causes rapid return of blood to the heart
This increases the preload of the heart, which can lead to hypertrophy of heart muscle and thus heart failure
Why is dialysis treatment not usually long term?
This is due to the additional complications associated with it and the fact that it does not reduce mortality rates
It instead should be thought of as a temporary measure to increase kidney function before a kidney transplant becomes available
