Renal replacement therapy: dialysis Flashcards
Functions of the kidneys
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
When is renal replacement therapy usually indicated?
When eGFR <10 ml/min
Types of renal replacement therapy (4)
Renal transplant
Haemodialysis
Peritoneal dialysis
Conservative Kidney Management
Define dialysis
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
Principles of dialysis
Diffusion
Ultrafiltration
What is required for dialysis to occur?
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
Difference between haemodialysis and peritoneal dialysis
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.
What are the permanent access points for haemodialysis?
Arteriovenous fistula - joining an artery and vein in your arm to make it stronger.
What are the temporary access points for haemodialysis?
Tunneled venous catheter and non-tunneled venous catheter
Usually inserted into neck region
What can pass freely across the membrane into the dialysate
Na+
K+
Ca2+
HCO3-
What restrictions must dialysis patients implement?
Fluid
Dietary - K+, Na+ and phosphate
What needs to be considered when working out fluid restrictions for dialysis patients?
Residual urine output - remaining in bladder
Interdialytic weight gain - excessive intake of fluids can cause weight gain - detrimental effects on survival/CVS/QOL
Describe peritoneal dialysis
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
What are the 2 types of peritoneal dialysis?
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
2 types of haemodyalisis
Home haemodialysis
Satellite / hospital haemodialysis
What is the most common osmotic agent for ultrafiltration of fluid in peritoneal dialysis
Glucose
What is dwell time?
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.
What is the dialysis solution made up of?
Water with salt and other electrolytes etc
Complications associated with peritoneal dialysis
Exit site infection, tunnel infection
Tube malfunction, abdominal wall herniae
PD peritonitis
Ultrafiltration failure - blood isn’t cleaned
Encapsulating peritoneal sclerosis
Which organisms are related to peritoneal dialysis peritonitis?
Gram +ve = skin contaminant
Gram -ve = bowel origin
Mixed = suspect complicated peritonitis e.g perforation
What is Encapsulating peritoneal sclerosis?
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.
Indications for dialysis in end stage renal disease? (5)
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
For haemodialysis patients what is their fluid intake usually restricted to?
500-800 ml/24 hours
which should = their urine output and insensible losses
Complications of haemodialysis
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)
How is the choice of dialysis made?
Patient’s own choice = most important.
Education and shared decision making required
What is Conservative kidney management?
Continued care without dialysis or a kidney transplant.
Supportive - symptomatic management, holistic MDT approach, anticipatory care planning
