Dialysis Flashcards
1
Q
What is Haemodialysis?
Outline its advantages & disadvantages
A
- Blood flows on 1 side of a semipermeable membrane while dialysis fluid flows in the opposite direction on the other side
- Diffusion!!
- Small solutes diffuse readily, larger less readily
- Ultrafiltration = removal of excess fluid by creating –ve transmembrane pressure
- 4hours 3x/week
- Problems
- Disequilibration syndrome
- Hypotension, arrhythmias
- Time consuming
- Access
- Fistula: thrombosis, stenosis, aneurysm, steal syndrome, ischaemia
- Temporary line: infection, blockage
2
Q
What is Haemofiltration?
Outline its advantages & disadvantages
A
- Blood filtered continuously across a highly permeable synthetic membrance, allowing removal of waste by convection
- Convection removes larger solutes at the same rate as small solutes (compared to diffusion)
- Ultrfiltrate substituted with equal volume of replacement fluid
- Negatives
- More expensive
- Takes longer than HD
- Advantages
- Less haemodynamic instability (and so used for critically ill patients)
3
Q
What is Peritoneal dialysis?
What are its advantages and disadvantages?
A
- PD fluid is introduced into peritonal cavity via a Tenchkoff-cathetar and uraemic solutes diffuse into it across the peritoneal membrane
- UItrafiltration is achieved by adding osmotic agents eg glucose to the dialysis fluid
- Advantages
- Simple to perform
- Requires less complex equipment than HD and is easier at hom
- Useful in children, elderyly and in those with CV disease
- Disadvantages
- Peritonitis (60% staphylococci, 20% gram -ve, 5% fungi)
- Exit-site infection
- Cathetar malfunction
- Loss of membrane function
- Obesity (glucose in dialysis fluid)
- Hernias
- Back pain
- Continuous ambultatory peritoneal dialysis (CAPD) uses smallest daily volume of dialysate fluid to prevent uraemia (4xday)
- Automated peritoneal dialysis uses a cycler machine to enhance solute and fluid removal (7-10hours at night)
