Hemofiltration

Hemofiltration is a method based on the elimination of waste products from the individual's circulatory system. In contrast to hemodialysis, filtration uses convective transport of solutes through a hemofiltration semipermeable membrane. Own technical equipment is a  dialysis monitor. It is a device that contains a blood pump that circulates extracorporeal blood from the patient's vascular access to the filter and back.

Principle


Blood is fed into extracorporeal circulation controlled by a dialysis monitor. Here, ultrafiltration (UF) of blood takes place through a semipermeable membrane, which shows a high degree of permeability even for molecules weighing up to 30,000 Da. This makes it possible to eliminate substances that cannot be removed by hemodialysis with a relatively high rate of success. During ultrafiltration, dissolved substances pass through the membrane together with the solvent (water). The speed of this transfer is influenced by many factors:


 * transmembrane pressure – the difference in pressure gradients on both sides of the membrane.

– at zero pressure gradient, UF is zero and increases linearly with increasing effective pressure gradient.


 * hemofilter ultrafiltration coefficient – ​​determines the amount of ultrafiltrate at a pressure gradient of 1 torr in 1 hour.

The volume of the filtered liquid from the circulation is then replenished with a substitution solution. This is automatically continuously prepared in the dialysis monitor and consists of treated water and mineral substances in an amount that corresponds to the amount of hemofiltration.

Usage
Hemofiltration expands the possibilities of using extracorporeal elimination in addition to hemodialysis and hemodiafiltration. This form of organ support is suitable for long-term use (CVVH – continuous veno-venous hemofiltration, respectively CAVH – continuous arterio-venous hemofiltration ) as a kidney replacement in critical patients, for example with a coagulation disorder. It can also be indicated for acute renal failure in a critical state (renal/non-renal), uremia (oliguria to anuria), general sepsis, ARDS (Acute respiratory distress syndrome), MODS (Multiple organ dysfunction syndrome), hepatorenal syndrome, cardiac failure or metabolic disruption.