Dialysis Flashcards
What are indications for dialysis?
1) Hyperkalaemia resistant to medical treatment (insulin dextrose) - can’t get rid of potassium in kidneys
2) Pulmonary oedema/fluid overload resistant to diuretics
3) Symptoms of uraemia (most common reason)
4) Acidosis
What are uraemic symptoms (symptoms relating to toxins building up in the body, non specific)?
1) Poor appetite
2) Vomiting
3) Weight loss
4) Lethargy and fatigue
5) Itching (build up of phosphate)
6) Malaise
What are the goals of dialysis?
1) Remove waste products (toxins, potassium)
2) Remove excess water
3) Maintain electrolyte and acid-base balance
What are the two types of dialysis?
1) Haemodialysis
2) Peritoneal dialysis
Describe haemodialysis
- Attached to a machine and blood is removed from the body
- It is put through a specific filter and then returned back to the body in a clean state
- The machine makes a fluid which runs in a countercurrent system with the blood across a semi-permeable membrane so need v pure water
- 3 times a week for 4 hours (what patient will tolerate, not medically best spacing of time)
- Need a fistula
- Flow of blood usually 200-300 ml/min
- Water requirement is 120L per session
Where can haemodialysis take place?
1) Hospital
2) Satellite unit
3) Home - good bc can do overnight every day instead of coming in 3 times a week however need lots of pure water so need to special plumbing and water supply
What do you need to put into the haemodialysis circuit tubing to prevent blood clotting?
Heparin
Describe the AV fistula
- Connecting vein directly to artery to give blood at a pressure between artery and vein
- Don’t want vein to collapse
- Two needles in artery is bad bc continuous puncturing of arteries causes problems with bleeding due to high pressures
- e.g. radiocephalic, brachiocephalic, brachiobasilic
- Needs to mature for 4-8 weeks after it is constructed
- Benefit = all natural, no plastic
What are potential complications of AV fistula?
1) Blows - blood leaks out of vein when needle goes in (instead of up needle) and moves to surrounding tissue causing bruising
2) Stenoses - narrowings form where joins have been made which can impinge on blood flow and where have lack of blood flow through the fistula it can clot or thrombose
Describe use of a graft in haemodialysis
- If a patient doesn’t have good vessels, can put bit of plastic inside (PTFE) which connects a native artery and vein
- Can be used immediately
- Same complications
- Plus risk of infection
Describe use of catheters in haemodialysis
- Used if patient doesn’t have weeks to wait and if high levels of toxins so can’t have anaesthetic (needed with graft)
- Instead dialyse them via a catheter until fistula has matured or graft is safe to do
- Inserted into big vein e.g. L/R internal jugular or femoral
- Can be temporary if someone needs emergency dialysis (high K, fluid overload) but after a week move on bc infection risk
- Use a tunnelled catheter which goes through skin tunnel reducing risk of it falling out and infection risk (gives time to spot it)
- Have two lumens - one for getting blood out and other for putting it back in
Describe the contents of dialysate
- Low in potassium and phosphate (but still need to follow specific diet)
- Neutral sodium
- High in bicarbonate
Why are dialysis patients usually restricted to 0.5L of fluid a day?
To avoid hypotension bc can’t remove more than 2-3L of water a session
What are potential complications of dialysis?
1) Hypotension bc of fluid removal
2) Septicaemia
3) Bleeding
4) Clotting in fistula and line (can lose fistula)
5) Dialyser reaction - inflammation in blood
6) Air embolus - can mimic PE in lungs
Describe peritoneal dialysis
- Home based done by patient
- Continuous ambulatory peritoneal dialysis
- Makes use of peritoneal membrane as semi-permeable membrane
- Creation of an osmotic gradient by addition of an osmotic agent (glucose)
- Fluid is removed by ultrafiltration caused by the osmotic gradient
- Solutes are transported by diffusion across a concentration gradient
- Membrane characteristics vary between patients
- Need to replace fluid and waste bags
- Should not be continued for > 5 years
