Renal Replacement Therapy
Kidney plays a vital role in maintaining body fluid and electrolyte balance. It removes waste products from body. Acutely or chronically detoriation of kidney function is life threatening and requires removal of waste, toxic products from body and maintenance of body fluid volume. This can be done Ly renal replacement therapy.
Indication for Renal replacement therapy:
“AEIOU”-
“A” – Acidosis with ph < 7.1
“E” – Electrolyte disarray
- Potassium > 6.5 mOsm/L,
- Hypernatremia > 160 mOsm/L
- Hyponatremia < 110 mOsm/L
“I” – Intoxicants (methanol ethylene glycol, Lithium);
“O” – Intractable fluid overload;
Oliguria < 200m1 in 12 hrs.
“U” – Uremic symptoms. (Uremic. encephalopathy, myopathy / neuropathy/ pericarditis nausea, seizure, pericarditis, bleeding).
- Urea >35 mOsm/L
- Creatinine > 400 mOsm/L
- Blood urea nitrogen (BUN) > 70-100 mg/dl
RRT is of following types:
- Haemodialysis / artificial kidney.
- Haemofiltration
- Haemodiafiltration
- Peritoneal dialysis
- Renal Transplant
Haemodialysis / artificial kidney
Dialysis is the process of removal of waste products by diffusion through semi permeable membrane to dialyzing fluid. Haemodialysis is dialysis of blood through artificial kidney. It involves gaining access to circulation and then then blood is pumped through haemodialyser (artificial kidney) which allows, bidirectional diffusion of solute through semi permeable membrane between dialyzing fluid (Dialysate) and blood along concentration garadient. clearance of the substance by diffusion is inversely proportional to the radius of the molecule. Therefore it clears larger molecules less effectively than smaller ones.
Complications during Hemodialysis
- Hypotension
- Muscle cramps
- Anaphylactoid reactions to the dialyzer
Hemofiltration
water and solutes are filtered from blood under pressure through a semipermeable membrane, this is known as convection. Then, suitable replacement fluid is added to blood after it exists from haemofilter. It is done at rate of 1-2 liter per hour (GFR: l5-30ml/min). It is of 2 types.
- Continuous arteriovenous hemofiltration (CAVH).
- The extracorporeal blood circuit is driven by arteriovenous pressure, but it has a Poor filtration rate and Clotting of the filter is common.
- Continuous erogenous Hemofiltration (CVVH).
- Extracorporeal blood circuit is Pump driven.
Haemodiafiltration (HDF)
Haemodiafiltration utilizes “convective” in combination with “diffusion” for clearance of substance. The convection is done by generating a positive pressure gradient across the dialyzer membrane. This pressure causes the plasma to flow across the membrane, pushing large-weight molecules across the membrane as well. Thus, Haemodiafiltration increases the clearance of larger molecules by large-volume ultrafiltration. To maintain fluid balance, HDF requires an infusion of a purified substitution fluid into the blood.
Peritoneal dialysis
It requires the insertion of a permanent silastic catheter in the peritoneal cavity Peritoneum acts as a semipermeable membrane. It is of two types.
Continuous ambulatory peritoneal dialysis (CAPD)
2 liters of isotonic dialysis fluid is placed in the peritoneal cavity for 4–6 hours. After which fluid is drained and new dialysis fluid is introduced at a frequency of 4 continuous cycles per day. The patient is mobile and can perform daily activities.
Automated peritoneal dialysis (APD)
A mechanical device is used to perform fluid exchange during the night or single cycle during the day.
Complications during Peritoneal Dialysis
- Peritonitis (elevated peritoneal fluid leukocyte count >100/mm3, out of which at least 50% are polymorphonuclear neutrophils).
- Catheter – associated non-peritonitis infections,
- Weight gain.
- Metabolic disturbances.
- Loss of albumin and other proteins through the peritoneal membrane.
- Residual uremia.
Renal transplant
It is a cost-effective treatment. It restores all functions of the kidney but requires long-term immunosuppressants. The graft can be taken from brain dead cadaver or a living donor.
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