Flashcards in Renal Therapeutics III: Renal Replacement Deck (41):
What is the aim of renal dialysis?
For patients with GFR
What are the 2 general techniques of renal dialysis?
Which 2 processes does dialysis try to mimic?
Ultra-filtration followed by reabsorption
How is ultra-filtration carried out in haemodialysis?
Fast cycles of fresh dialysis fluid = more effective than peritoneal dialysis
How is ultra-filtration carried out in peritoneal dialysis?
Patient's own peritoneal membrane
Dialysis reaches equilibrium before fluid change
When is dialysis used?
ARF (in oliguric phase)
What is required in order to mimic ultra-filtration?
Membrane similar to glomerular basement membrane
Differs in pore size
How is water removed in haemodialysis?
By hydrostatic force
How is water removed in peritoneal dialysis?
By osmotic pressure (between blood and dialysis fluid)
How is waste removed during dialysis?
Blood is exposed (through a membrane) to a solution with a low concentration of substances to be removed
How is conservation of useful substances mimicked?
Tubular reabsorption does not exist
Replacement dietary supplementation oradding substances to dialysis fluid = transfer to patient
Why is heparin added to the blood during dialysis?
To prevent thrombosis in the blood circuit of the dialysis machine
Prevents air bubbles in blood getting into body
What does the dialysis fluid remove from the blood?
Calcium (also in)
Sodium (also in)
What does the blood take up from the dialysis fluid?
Calcium (also out)
Sodium (also in)
Name the 4 haemodialysis techniques
What is conventional haemodialysis?
Low-flux membranes allow diffusive, but little convective solute removal
Middle molecule clearing is poor
What is haemofiltration?
Purely convective treatment
Poor small molecule clearance
Middle molecule clearance excellent
Not a long term treatment for ESRF
What is high-flux haemodialysis??
Highly permeable membranes used
= Good diffusive removal of middle molecules and small solutes
What is haemodiafiltration?
Haemofiltration (convective) but high flux haemodialysis (=highly permeable membranes)
List 5 side effects of haemodialysis
Low blood pressure - due to fluid loss
Muscle cramps - during dialysis due to fluid loss
Itchy skin - due to potassium build up, can be managed by a low potassium diet
What is peritoneal dialysis?
Home-based renal replacement therapy for patients with ESRF
2L of sterile dialysis fluid (dialysate) runs directly into the peritoneal cavity using a cathetar
Dialysis takes place between the blood in peritoneal capillaries and the dialysate, across the peritoneal membrane
Dialysate drained out
How is water removed from the blood in peritoneal dialysis?
The dialysate contains lots of glucose = osmotic gradient
Therefore water can be removed via osmosis
Amount of water removal can be adjusted by altering glucose concentration
How is the pH of the blood buffered?
By absorption of lactate and bicarbonate from the dialysate
What are the 3 techniques of peritoneal dialysis?
Intermitted peritoneal dialysis (IPD)
Continuous ambulatory peritoneal dialysis (CAPD)
Automated peritoneal dialysis (APD)
What is intermitted peritoneal dialysis (IPD)?
Carried out over 24-48 times over 1-2 days
30 mins each
Repeated 2-3 times weakly
What is continuous ambulatory peritoneal dialysis (CAPD)?
Patient carries fluid in abdomen continuously
Changed 2-5 times daily
Closest method to normal kidney function
What is automated peritoneal dialysis (APD)?
Machine to switch between bags
used at home
More rapid cycle
Night-time exchanges might be enough
How can drugs be given in peritoneal dialysis?
Can be given in the CAPD fluid (abdomen)
e.g. antibiotics and insulin
List 2 common problems with peritoneal dialysis
Infection - peritonitis or exit site
Hyperglycaemia - glucose in dialysate causes this and obesity, especially in CAPD
List 2 advantages of PD over HD
Patient autonomy and independence
Lifestyle advantages (e.g. easier work and travel)
List 2 disadvantages of PD vs HD
Peritonitis and exit site infection
Patient or carer needs to be able to perform technique
List 3 things that would make a deceased person's kidney less attractive to donate
If the deceased donor has suffered from:
Problems with hormone levels
What is histocompatibility?
What are the 2 important immunological criteria for histocompatibility?
Human leucocyte locus-A (antigen compatibility)
Better matching kidney = reduced immunosuppressant doses
Describe the process of the surgical procedure of a kidney transplant
Organ placed extraperitoneally (peritoneum preserved for eventual dialysis)
Connected to blood circulation and and ureter implanted to bladder
Original kidneys usually left in except if problems e.g. hypertension, stones, tumours etc
Name the 3 types of rejection which could occur after a transplant
Hyperacute or immediate rejection
Explain what a hyperacute/immediate rejection is
Caused by pre-existing antibodies
Happens within hours
Untreatable and rare
Results in renal vascular thrombosis
Explain what an acute rejection is
Most common form
T cell-mediated response to antigens
Results in vascular and tubular damage
Explain what a chronic rejection is
After the first few months
Immune-complex deposition within glomeruli and renal vessels
Leads to glomerulonephritis = irreversible
What are the 3 areas of medical management for renal transplants?
1. Initial choice and subsequent modulation of immunosuppressant regimen to prevent early & acute rejection
2. Management of complications and side effects of immunosuppressant therapy
3. Management of poorly function renal transplant