Hemofiltration and Ultrafiltration: Nursing Concerns

Abstract

In the past two decades, new methods and techniques of extracorporeal therapy have brought about vast improvement and concurrent expansion of its clinical role. Previously, dialysis and isolated ultrafiltration had been the mainstay therapy for patients with acute oliguric renal failure. Dialysis, from a clinical standpoint, is the removal of endogenous and exogenous toxins and other harmful substances from the body fluids by differential diffusion across a semipermeable membrane. Mass transfer across a semipermeable membrane is based on two mechanisms, diffusion and ultrafiltration. Diffusion, a conductive process, is a passive transfer of solutes across a membrane. Ultrafiltration is a convective process in which simultaneous transfer of solutes and solvent across the membrane occurs. In the past, ultrafiltration procedures were performed only in isolated fashion; either predialysis or postdialysis, ultrafiltration was used to remove significant amounts of fluid in relatively small periods of time, i.e., 2–6 hours. This rapid removal of 2–3 liters of fluid could produce hemodynamic instability in acutely ill patients.