DEFINITIONS

Hemodialysis (HD)

The blood passes through an extracorporeal circulation where it is separated from dialysis fluid by artificial semi-permeable membrane. Solutes move across the membrane only by diffusion. The dialysis solution comprises water and electrolytes. The dialysis membrane is usually made from cuprophane, a cellulose derivative. Newer synthetic membranes of polymeric structure are more permeable to water and solutes and more biocompatible with the blood than cuprophane membranes.

 Hemofiltration (HF)

Hemofiltration is a form of dialysis in which  a negative pressure is created on the side of a highly permeable dialyzer (Hemofilter) opposite to the blood comartment.This sucks the plasma fluid and the solute dissolved in it across the membrane.This process is known as ‘Convection’. High volume of plasma is ultrafiltrated simultaneously replaced by pyrogen free hemofiltration fluid intavenously. The basic difference between hemodialysis and hemofiltration is in the principle of solute transport. During hemodialysis the solute is removed by diffusion and the fluid by ultrafiltration. By contrast, during hemofiltration, the solute removal is accomplished by convection, that is solvent drag.

Continuous Arterivenous Hemofiltration (CAVH)

CAVH is an extracorporeal treatment in which fluid, and electrolyte, and low molecular weight solute are removed from the body by convective transport.

The technique utilizes the patient arterial pressure to move the blood in the circuit and an ultrafiltrate with the same characteristics of plasma is generated. The substitution of the amount of fluid lost by ultrafiltration with sterile replacement solution permit: (1)To correct electrolyte and acid base imbalance. (2)Lower the patient’s BUN concentration

Hemodiafiltration (HDF)

A combined hemodialysis and hemofiltration procedure. Dialysis solution and highly permeable membrane are used to obtain diffusion and ultrafiltration. The fluid balance is maintained by infusing a hemfitration fluid.

 Isolated Ultrafiltration (IUF)

Isolated Ultafiltration is a method whereby fluid, electrolytes and substance with low molecular weight are removed from the plasma water by means of convection. Half to one and a half liters can be removed per hour using conventional hemodialyser. No diffusion occurs during this procedure.When UF precedes or follows hemodialysis; the combined process is called Sequential UF, or Sequential dialysis.

Hemoperfusion (HP)

HP is a process whereby blood is passed through a cartridge packed with activated charcoal or carbon, (i.e. the cartridge paced instead of dialyser in the blood circuit). It is more effective than hemodialysis in clearing the blood of many protein-bound drugs, because the charcoal will compete with the plasma protein in for the drug, adsorb the drug, and thereby remove it from the circulation. Similarly, hemoperfusion will remove many lipid soluble drugs from the blood much more efficiently than hemodialysis. Hemoperfusion is preferred than Hemodialysis in Glutethimide, Methaqualone, Theophylline and Phenobarbital drug poisoning.

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