Renal Replacement Therapy Flashcards
What are the normal functions of the kidney?
Excretion (of waste and foreign chemicals) Regulation of: Water and electrolyte balancer Body fluid osmolarity Arterial pressure Acid base balance
Erythrocyte production
Vitamin D production
What does dialysis do for the kidneys?
Excretion of metabolic waste products and foreign chemicals.
Control water and electrolyte balances
Acid base balance
What is the aim of RRT (renal replacement therapy)?
RRT mimics the excretory function of the normal kidney.
Eliminating nitrogenous waste
Maintaining normal electrolyte concentration
Preventing systemic acidosis
Maintaining a normal extracellular volume
When do you start dialysis?
Uraemic symptoms
Uncontrolled hyperkalaemia
Uncontrolled fluid overload
What are the renal replacement therapy options?
Haemodialysis
Peritoneal dialysis
Kidney transplantation
Conservative management
Haemodialysis
In haemodialysis an artificial kidney (haemodialyzer) is used to remove waste and extra chemicals and fluid from the blood stream.
How does a dialysis machine work?
Blood is pumped around an extracorporeal circuit through a semi-permeable membrane (dialyser) before being returned to the circulation. In a dialyser the dialysate flow in the opposite direction to blood.
What is the peritoneal membrane?
A semi-permeable fine layer of tissue that lines the peritoneal cavity covering the stomach, liver, spleen and intestines.
What are the benefits of peritoneal dialysis?
The peritoneal membrane has a rich blood supply that is ideal for filtering wastes and extra water from the blood.
Cause and example:
Pre-renal AKI
Cause: Poor perfusion
Example: Blood loss, sepsis, ACE inhibitors, NSAID’s
Cause and example:
Renal AKICause: tubular damage
Cause: tubular damage
Examples: Crush injury (myoglobin), mismatched transfusion (haemoglobin), poison (mercury, clostridium toxin). Diabetes / Hypertension
Cause and example:
Post-renal AKI
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
CAPD
Chronic abumlatory peritoneal dialysis
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
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