Renal Replacement Therapy Flashcards
Contrast haemodialysis and haemofiltration.
Haemodialysis Haemofiltration
Removes solute by diffusion Removes solutes by convection
(down osmotic gradient)
Low Mw solutes removed Mw does not affect clearance rate
more easily
Dialysate + waste products Plasma + water + waste products
removed removed (water replaced)
Outline how haemodialysis works.
Arteriovenous fistula created (vein is arterialised - can withstand high pressure) - can be radiocephalic, brachiocephalic, etc.
Removes solutes by diffusion - uraemic toxins move across membrane down conc. gradient (dialysate & blood flow countercurrent to maximise solute clearance)
Clearance inversely related to Mw of solute
Solute removal directly related to dialysate flow rate
What are the advantages and disadvantages of unit-based haemodialysis compared to other renal replacement therapies?
Advantages:
- less responsibility
- days off
Disadvantages:
- travel time + waiting
- tied to dialysis times
- big restriction to fluid/food intake
What are the contraindications and complications of haemodialysis?
Contraindications:
- failed vascular access
- heart failure
- coagulopathy (need to clot after removing)
Complications:
- lines: infection, thrombosis, venous stenosis
- AVF: thrombosis, bleeding, access failure, “steal syndrome” (downstream ischaemia due to fistula)
- CVS instability
- chronically “unwell”
- accumulate morbidities e.g. CVS, bone
What are the advantages and disadvantages of home-based haemodialysis compared to other renal replacement therapies?
Advantages:
- better high Mw clearance (time-dependent)
- fewer medications
- feel better
Disadvantages:
- requires someone else at home e.g. needle falls out —> bleed to death
Outline how peritoneal dialysis works.
Peritoneum used as membrane
Dialysate put into peritoneal space via catheter and drained later
- continuous ambulatory PD = 4-5 bags per day
- automated PD = overnight dialysis
What are the advantages and disadvantages of peritoneal dialysis compared to other renal replacement therapies?
Advantages:
- self sufficience/independence
- fewer restrictions on fluid/food intake
- easier to travel (continuous ambulatory PD)
- better initial preservation of renal functions
Disadvantages:
- frequent daily/overnight exchange
- responsibility
What are the contraindications and complications of continuous ambulatory peritoneal dialysis?
Contraindications:
- failure of peritoneal membrane
- adhesions, previous abdominal surgery, hernia, stoma
- patient/carer unable to connect/disconnect
- obese/large muscle mass (less efficient)
Complications:
- peritonitis (~ every 20 months), exit/tunnel site infections
- ultrafiltration failure
- leaks (scrotal/diaphragmatic) —> cannot continue PD
- herniae development
Outline how renal transplants work.
Transplant kidney with ureter and blood supply attached transplanted without removing diseased kidneys
- live donor (related or unrelated)
- deceased after brain death
- deceased after circulatory death or non-heart-beating (increased risk of damage to kidney)
Kidneys matched according to blood (ABO) & HLA (not as much of a problem with live donors due to better blood supply) as well as age/length of time on waiting list
Transplant medications: - anti-rejection - antibiotics for PCP - anti-virals (if CMV-ve) etc.
What are the advantages and disadvantages of renal transplant compared to other renal replacement therapies?
Advantages:
- better quality of life
- reduced morbidity and mortality compared to dialysis
Disadvantages:
- risk of malignancy & infection due to immunosuppression
- risk of diabetes & hypertension due to medications (NODAT = new-onset diabetes after transplant)
- peri-operative risk (greatest in first 3 months)
What are the signs & symptoms in end-stage renal dialysis?
- pain (bone, due to renal failure, dialysis related etc.)
- constipation
- fatigue
- nausea/lack of appetite (anorexia)
- pruritis
- restless legs/cramps
- sleep disturbance
What process causes acute kidney transplant rejection?
Cell-mediated rejection most common form of early rejection
(can be humoral as well)
Difference can be determined by biopsying the transplant kidney e.g. ?presence of mononuclear cells (cellular rejection), ?fibrin thrombi/fibrinoid necrosis (antibody-mediated rejection)
How is acute kidney transplant rejection treated?
Immunosuppressants
High dose methylprednisolone (more serious = antithymocyte globulin)
Give some examples of disease risks renal transplant patients are susceptible to.
Immunosuppression:
- malignancy (esp. skin cancer & lymphoma)
- CVD (also due to previous renal impairment, hypertension, hypercholesterolaemia, etc.)
- osteoporosis (steroids)
- opportunistic infections e.g. CMV pneumonitis, pneumocystis jirovecii pneumonia (PCP)
Chronic allograft nephropathy (de novo synthesis of donor specific antibodies & non-immunological factors)
