Dialysis + Transplant Flashcards
Haemodialysis Principles
Blood + dialysate flow in opposite directions –> countercurrant mechanisms maintain conc. gradient throughout exchange surface
For diffusion losses to occur–> small amounts K+ and other solutes in dialysate, so K+ diffuses out of blood
For additions to occur–> large vol of bicarbonate in dialysate, flows into blood
For water loss–> increase pressure of blood + decrease pressure of dialysate
Haemodialysis Circulatory access- temporary
Central venous catheter (enters internal jugular + sits in right atrium)
Haemodialysis Circulatory access- permanent
Arterio-venous fistula (artery + vein joined together to arterialise vein) where blood can be removed + added back in
Haemodialysis- GFR
When patient on machine, clearance is excellent, but rest of time have no kidney function
Averages out to GFR 10-12ml/min
Haemodialysis Advantages
Better clearance
Short time for treatment
Not dependent on patient competence
Haemodialysis Disadvantages
Hospital Limited by staff and spaces Requires circulatory access- complications including thrombosis + infection (LMWH + antibiotics) Cardiovascularly demanding Restricted diet
Peritoneal dialysis Principle
Catheter placed in patient’s abdomen –> travels under skin + enters peritoneal cavity at midline
Uses peritoneum as semi-permeable membrane
Capillaries run outside the peritoneal membrane carrying solutes etc.
Dialysate pumped into peritoneal cavity + exchange processes occur across the peritoneal membrane
Dialysate contains low conc. of waste product (to encourage to diffuse out of blood) and high conc. glucose + larger molecules (to promote diffusing into blood)
Can also deliver things to patient such as bicarb/lactate for buffering + amino acids for nutrition
Closed space –> conc. gradients equal out –> have to drain fluid + replace
Peritoneal dialysis GFR
Slightly less efficient than haemodialysis
GFR around 7-8ml/min
Some renal function must remain
Can be done almost continuously unlike haemodialysis
4 x 2L exchanges per day- 30 mins per exchange
Peritoneal Dialysis advantages
Easy access
Haemodynamically stable
Increased patient mobility –> do not have to remain close to hospital
Home based –> maintains patient independence
Peritoneal Dialysis disadvantages
Lower rate of clearance Infection (peritonitis) and adhesions can occur Membrane failure Intra-abdominal catheter required Dependent on patient competence
Renal transplant prognosis
Lower risk of death compared to both types of dialysis
Initial risk of death is higher in those receiving a transplant due to surgical complications, immunosuppression and recovery period
Takes about half a year for RR of death to become lower than patients remaining on transplant risk, but after this time risk is continuously getting lower
Renal transplant advantages
Increased survival Continuous therapy (dialysis) not needed
Renal transplant disadvantages
Risk of rejection
Lifelong immunosuppression
Have to find suitable donor
Psychological problems
Blood group
People can’t receive transplant to which they have pre-formed antibodies against
All blood groups can donate to themselves
O can donate to anybody but only receive from O
A and B can donate to AB
A and B cannot donate to each other
HLA Class I
Present in all cells
A,B,C
HLA Class II
Present in APCs
DR, DQ, DP
HLA genetics
Found on chromosome 6
Inherited via simple Mendelian inheritance
Everyone has 2 alleles for each HLA subtype
HLA compatibility
0MM= all same types
6MM= none of same types
HLA DR, B and A most important
