Wednesday, 10 November 2010

MRCP revision battle 45.1: Dialysis and complications

Back to my old nemesis renal medicine for another 7 battles...

MRCP revision battle 45.1: Dialysis and complications
MRCP revision battle 45.2: Anaemia in chronic renal failure
MRCP revision battle 45.3: Diuretics
MRCP revision battle 45.4: Proteinuria
MRCP revision battle 45.5: Renal osteodystrophy
MRCP revision battle 45.6: Radio-contrast nephropathy
MRCP revision battle 45.7: Minimal change disease

MRCP revision battle 45.1: Dialysis and complications

Lets start with a very matter-of-fact battle on dialysis and its complications

Brief overview of types of renal replacement therapy
  1. Haemodialysis
    • semi-permeable membrane
    • solute transfer by diffusion
    • excess fluid removed by creating a negative transmembrane pressure = ultrafiltration
  2. Haemofiltration
    • highly permeable membrane
    • solute transfer by convection
    • ultrafiltrate replaced by an equal volume of substitute fluid
    • takes longer and is more expensive than haemodialysis but less haemodynamic instability so used for critically ill patients
  3. Peritoneal dialysis
    • dialysis fluid put into abdominal cavity via tenchkoff catheter
    • solutes diffuse across peritoneal membrane
    • ultrafiltration achieved by adding glucose to the dialysis fluid

Complications of dialysis
  • Disequilibration syndrome
    • occurs on initial dialysis
    • manifests as nausea, vomiting, headache and altered consciousness
    • caused by rapid changes in plasma osmolality
  • Vascular disease
  • Heart valve calcification - especially aortic valve
  • Beta-2 microglobulin amyloidosis
  • Arthritis
  • Infections

Now to consider anaemia in renal failure...