L5 - Renal Replacement Therapy Flashcards
1. Describe the principles of normal kidney function 2. Describe principles of haemodialysis, haemofiltration and haemodiafiltration and how they differ from normal kidneys 3. Describe principples of peritoneal dialysis 4. Explain indications for renal replacement therapies 5. Explain principles of kidney transplantation 6. Compare and contrast each RRT method 7. Survival of patients on kidney replacement therapies and conservative management as RRT method
Summarise renal failure
- Acute
- pre-renal
- renal
- post-renal - Chronic
Chronic renal failure
Permanent loss of renal function, may lead to ESRF
- end stage renal failure
Cause and example:
Pre-renal
Cause: poor renal perfusion
Examples: Blood loss, sepsis, Ace inhibitors, NSAIDs
Cause and example:
Renal
Cause: tubular damage
Examples: Crush injury (myoglobin), mismatched transfusion (haemoglobin), poison (mercury, clostridium toxin)
Cause and example:
Post-renal
Cause: Obstruction
Examples: bilateral ureteric obstruction (stone, tumour, retroperionteal fibrosis or surgical injury) Unilateral obstruction of solitary kidney
Crush Syndrome
Crush injury - prolonged continuous pressure on muscle tissue
- Muscle injury
- can cause large quantities of potassium, phosphate, myoglobin, creatine kinase and urate
- to leak into the circulation.
Give brief investigation of renal failure
- Urine assessed for haematuria, proteinuria, looked at microscopically for casts
- USS, kidney size: hydronephrosis?
- X-ray: stones in UT
- RBC: microscopically
Fragmented or dysmorphic RBC found in urine sample may indicate..
Glomerular region
- see in proliferative glomerulonephritis and immuniglobin A nephropathy
Describe how CAPD may be carried out?
Chronic abumlatory peritoneal dialysis
- Silicon catheter inserted into abdo cavity.
- Dialysate fluid runs through multiple holes into abdomen.
- Left for several hours
- Fluid allowed to drain out
When is CAPD not possible?
If patient has undergone lots of previous abdominal surgery with adhesion.
Complications of CAPD
loads
Peritonitis. Hernia (incisional, inguinal, umbilical) Genital oedema Gram negative sepsis Staphylococcus Back pain Fluid retention
Describe haemodialysis
- Blood from patient flows through dialysing membrane.
- Solutes allowed to pass into dialysis fluid thus purifying blood.
How common is death by myocardial infarction (heart attack) in dialysis patients and why?
20x more likely in dialysis patients.
Due to:
- Hyperlipidaemia
- Hypertension
- Left ventricular hypertrophy
The immunocompromised nature of ESRF patients undergoing dialysis may lead them at risk of…
- Malignancy
- Hepatitis
- Tuberculosis
Describe method of dialysis
- Create peripheral fistula
- Creates large hypertrophied vessel that can repeatedly be needled allowing blood to be diverted into dialysis machine.
- OR permanent plastic catheter inserted into internal jugular or subclavian vein
Describe the formation of the arteriovenous fistula
- Artery and vein anastomosed.
- Usually radial/ brachial artery and cephalic vein.
- Creates large hypertrophied vessel.
- hypertrophy refers to an increase and growth of muscle cells.
During renal transplantation what is the role of the Carrel patch?
- Patch of aortic wall.
2. Excised with renal artery to facilitate arterial anastomosis onto the recipients external iliac artery.
Which kidney is normally removed in a donor?
Left kidney.
- Has a longer renal vein
- makes operation easier
Briefly describe the recipient surgery during kidney transplantation?
- Aortic patch present.
- Renal vein anastomosed end to side with the external iliac vein
- Renal artery anastomosed end to side with the external iliac artery - Ureter then anastomosed to bladder mucosa.
Briefly describe recipient surgery during kidney transplantation, when there is no aortic patch?
Renal artery usually anastomosed end to end to the internal iliac artery.
Ureter then anastomosed to bladder muscosa.
After kidney transplant, blood supply to the ureter is completely dependent on what artery?
Renal artery
State criteria for patients to begin dialysis?
GFR has reached 10ml/min
Diabetic patients
- GFR reached 15ml/min
Uraemic symptoms.
Uncontrolled hyperkalaemia
Uncontrolled fluid overload
Patient stage 5 CKD.
When should peritoneal dialysis be considered as 1st choice for dialysis over haemodialysis?
- Patient <2 y/o
- patient residual renal function
- Adults without significant associated comorbidities.
What are indications for dialysis in AKI?
- Uraemia
- (pericarditis, gastritis, hypothermia, encephalopathy) - Fluid retention
- pulmonary oedema - Sever hyperkalemia
- >6.5mmol & unresponsive to treatment - Serum Na+ out of range 120-155mmol
- Severe pH disturbance <7
What levels of urea and creatinine would indicate severe renal failure?
Urea > 30mmol/L
Creatinine > 500umol/L
Blood in patients needing dialysis would have high concentrations of what…
Urea
Creatinine
Potassium
Briefly describe process of haemodialysis
Blood drawn from arteriovenous fistula.
Circulates through dialyser.
Then returned to fistula.
What is constantly infused during dialysis and why?
Heparin
- anticoagulant, blood thinner
Complications of haemodialysis
- Hypotension, cardiac arrhythmia, air embolism
- Nausea, vomiting, headache
- Fever
Compare haemodiafiltration with standard haemodialysis
RRT.
Increased clearance of larger toxins by large volume ultra filtration.
Standard haemodialysis
- Toxin clearance by diffusion inversely proportional to radius of the toxin molecule.
- hence larger toxins are cleared less effectively than smaller ones
Aims of RRT
Mimic excretory function of normal kidneys:
- eliminating nitrogenous, small molecular waste
- maintain normal electrolyte concentrations
- prevent systemic acidosis
- maintain normal extracellular volume
Describe principle of dialysis in a dialyser
Blood pumped around an extracorporeal circuit through a semi permeable membrane, before returning to circulation.
Dialysate flows opposite direction to blood.
Small solutes cross membrane via diffusion.
What controls fluid removal in dialyser?
Transmembrane pressure allows controlled fluid removal by ultrafiltration.
What composes the dialysate?
Acid and bicarbonate mixed to the correct strength, treated with water.
What is an alternative to using an arteriovenous fistula?
permanent plastic catheter inserted into internal jugular or subclavian vein
Describe the peritoneal membrane?
- Semi permeable fine layer of tissue lining the peritoneal cavity.
- Covers stomach, spleen, liver and intestine that are folded into the sac that it forms.
Why is the peritoneal membrane ideal for filtering waste?
Rich blood supply.
Describe the structure of the peritoneal membrane?
- Mesothelial cell monolayer.
2. Intersitium underneath: contains connective tissue, fibers, lymphaics and capillaries
Describe what is meant by the tissue type of kidney?
Collection of HLA antigens on the tissue of either donor or recipient.
Examples:
A2, A3, B35, B40, DR6, DR71
What is the main role of immunosupressants given post transplant?
Drugs are targeted at reducing T-cell proliferation
Describe some transplant complications?
Acute rejection. Ureteric problems. Cancer: skin, lymphoproliferative Diabetes Dyslipidaemia Hypertension CKD Primary non-function
What is the leading cause of morbidity in haemodialysis patients?
Cardiovascular disease.
Cardiovascular mortality is higher for haemodialysis patients than for the normal population.
