Transplantation Flashcards
Dialysis depends on what type of mechanism
Diffusion
When is dialysis indicated
Acidosis
Electrolyte disturbance - persistent hyperkalaemia
Intoxication
Oedema - persistent pulmonary oedema
Uraemia - pericarditis, encephalopahty
How is vascular access for dialysis established
Arteriovenous fistula
Arteriovenous graft
Tunnelled central venous catheter
Most common way of vascular access for dialysis
Arteriovenous fistula
What are the problems with arteriovenous fistula
Requires surgery
Requires maturation of 6-12 weeks before can be used
Steal syndrome
Blood clots
Why is tunnelled central venous catheter not commonly used
High risk of infection
What is the most common pathogen causing infection of tunnelled central venous catheter
S aureus
Management of infection of TCVC
vancomycin and gentamicin
Line removal or exchange
What are the 3 types of dialysis
Haemodialysis
haemofiltration
Peritoneal dialysis
How does haemodialysis remove solutes
Mainly Diffusion -> convection -> adsorption (least dependent on)
What is convection
movement of molecules through a semipermeable membrane associated with the fluid being removed during ultrafiltration
Independent of solute concentration
What is adsorption
affects plasma proteins - stick to the membrane surface and are removed by membrane binding
How does haemofiltration remove solutes
Mainly convection -> diffusion -> adsorption
What factors affect convection
- Water flux
- Membrane pore size
- Pressure difference (hydrostatic pressure)
- Viscosity of the fluid
What is peritoneal dialysis
Solute removal is by diffusion of solutes across the peritoneal membrane (which is semi-permeable)
Uses the peritoneal membrane as filter
Describe the mechanism of peritoneal dialysis
- Dialyslate fluid is injected into the peritoneal cavity
- When the bag is empty, you disconnect it and place a cap on your catheter so you can move around and do your normal activities
- While the dialysis solution is inside your belly, it causes wastes and fluid to be drawn into the peritoneal fluid due to high dextrose concentration of the dialysis solution
- then after a few hours, the solution and the wastes are drained out of your belly into the empty bag.
When is peritoneal dialysis used
As a stop gap to haemodialysis
For young patients who do not want to go to the hospital all the time
Complications of peritoneal dialysis
Peritonitis
Peritoneal membrane failure - unable to filter the wastes out
Hernia
How may peritoneal dialysis cause hernias
Due to increase in intra-abdominal pressure
What pathogen commonly causes peritonitis due to peritoneal dialysis
Staph epidermidis
Management of peritonitis in patients with peritoneal dialysis
vancomycin + ceftazidime added to dialysis fluid
vancomycin added to dialysis fluid + ciprofloxacin by mouth
Complications of haemodialysis / haemofiltration
Hypotension
Hemorrhage - ruptured arteriovenous fistula
thrombosis
infection
Arrhythmia
Endocarditis
How does haemo-dialysis / haemofiltration cause arrhythmia
electrolyte imbalance
myocardial ischaemia (due to clots)
What lifestyle modifications are patients required to do if they receive dialysis
Fluid restriction - 1L a day
Low salt diet
Low potassium diet
Low phosphate diet
Phosphate binders - sevelamer
Contraindications of renal transplant
Malignancy
Active HCV/HIV infection
Untreated TB
Severe diseases - airway, vascular
What are the aspects of tissue typing for matching a renal transplant
Blood group
HLA matching
If there are any previous transplants / blood transfusion / pregnancy
- this can cause existence of other antibodies
What are the HLA groups
Class 1 - A, B and C
Class 2 - DP,DQ and DR
Which HLA antigen is the most important to be considered when matching HLA groups
DR > B > A
Complications of renal transplant
Rejection
Thrombosis
Bleeding
Wound infection
Acute Tubular Necrosis of the graft
What is acute tubular necrosis of the graft
When the transplant does not start producing urine immediately
Rejection of renal transplants can be classified into
Hyperacute rejection
Acute rejection
Chronic rejection
What is considered as hyperacute rejection
Occurring within minutes - hours
What causes hyperacute rejection
Due to pre-existing antibodies
Which type of hypersensitivity is hyperacute rejection part of
Type II (IgG or IgM mediated)
What happens in hyperacute rejection
widespread thrombosis of graft vessels → ischaemia and necrosis of the transplanted organ
Is hyperacute rejection salvageable
No, the transplant must be removed
What is considered as acute rejection
occurring < 6 months
What causes acute rejection
due to mismatched HLA
Which type of hypersensitivity is acute rejection part of
Type 4 - it is T cell mediated
Acute rejection is usually
asymptomatic
Signs of acute rejection
Rising creatinine
Pyuria (pus in pee)
Proteinuria
Is acute rejection salvageable
May be treated with increased immunosuppression
What is classified as chronic rejection
occurring after 6 months
What is chronic rejection
antibody and cell-mediated mechanisms cause fibrosis to the transplanted kidney -> slow decline in renal function
What occurs in chronic rejection
Slow decline in renal function
Recurrence of previous renal disease
- membranoproliferative GN
- IgA GN
- focal segmental GS
Example regime for immunosuppression for patients with renal transplants
Initial: ciclosporin / tacrolimus + mAB (dacluzimab)
maintenance: ciclosporin/tacrolimus + Mycophenolate mofetil (MMF
Add steroids if acute rejection episodes
tacrolimus can cause
impaired glucose tolerance and diabetes
hypertension
hyperlipidaemia
cyclosporin can cause
impaired glucose tolerance and diabetes
hypertension
Patients with renal transplant on immunosuppressants should be monitored regularly checking for
Cardiovascular disease - due to tacrolimus and cyclosporin potentially causing hypertension, hyperlipidaemia
Renal failure
Malignancy - skin cancer
Why are patients with renal transplants on immunosuppressants more at risk of skin cancer
Immunosuppression
Ciclosporin increases risk of SCC/BCC
