Dialysis

Question 1

Dialysis : Indications for Acute Dialysis

Answer 1

1. Severe acidosis and unresponsive to treatment
2. Electrolyte abnormalities -** refractory hyperkalaemia**
3. Overdose of medication
4. Severe and unresponsive pulmonary oedema
5. Uraemia symptoms such as seizure of reduced consciousness

Question 2

Dialysis : Indications for Long-term Dialysis

Answer 2

• End stage renal failure : CKD stage 5

Question 3

Dialysis : Peritoneal Dialysis MOA

Answer 3

1. Peritoneal membrane is used as the filtration membrane.
2. A special dialysis solution containing dextrose is added to the peritoneal cavity
3. Ultrafiltration occurs from the blood, across the peritoneal membrane into the dialysis solution
4. The dialysis solution is then replaced, taking away the waste products which have filtered the blood into the solution.
5. Involves : Tenckhoff catheter which is inserted into the peritoneal cavity with one end outside to allow access for inserting and removing the dialysis solution.

• Continous Ambulatory Peritoneal Dialysis - dialysis solution is in the peritoneum at all times and is changed at various regimes throughout the day.
• Automated dialysis - peritoneal dialysis occurs overnight for around 8-10 hours

Question 4

Dialysis : Peritoneal Dialysis - Complications

Answer 4

1. Peritonitis - infusions of glucose allow for bacteria growth. Add antiviotics to peritoneal fluid.
2. Peritoneal sclerosis - scarring and thickening of the peritoneal membrane
3. Weight gain from absorbing dextrose in the dialysis solution
4. Ultra filtration failure - over time patient can start to absorb the dextrose in the filtrate solution reducing how steep the concentration gradient is thus making the ultrafiltration less effective in filtering out toxins from the blood.

Question 5

Dialysis : Haemodialysis MOA

Answer 5

Blood is filtered by the haemodialysis machine - typical regime is around 4 hours a day for 3 days a week.

Access for abundant blood supply is needed - this done via

1. Tunneled cuff catheter :
   - catheter tube is inserted into the subclavian or jugular vein with the tip sitting in the superior vena cava or right atria.
   - It has two lumens, one where the blood exits the body (red) and one where blood enters (blue).
2. A-V fistula
   - artificial connection between an artery and a vein, bypasses the capillary system and allows for blood to flow under high pressure. - This provides permenant access to blood with high arterial pressure.
   Requires surgical intervention - 1-4 months of maturation time post op before it can be used.

Question 6

Dialysis :Haemodialysis - AV fistula complications

Answer 6

1. Anuerysm / Infection / Thrombosis /Stenosis
2. STEAL syndrome : inadequate blood flow to the limb distal to the AV fistula.
   * The AV fistula steams blood from the distal limb and blood is diverted away from the limb causing distal limb ischaemia
3. High output heart failure -
   * AV fistula blood is flowing very quickly from the arterial to venous system resulting in a rapid return of blood to the heart via the vena cava
   * this increases the preload in the heart. Thus causing right ventricular hypertrophy and heart failure.