[Extracorporeal renal replacement therapies in acute renal failure]

The most serious forms of acute renal failure (ARF) are nowadays encountered in the intensive care unit (ICU), where up to 25% of new patients are reported to develop ARF. Lethality rates may reach 50 to 90% when the ARF is part of a multiple organ dysfunction syndrome. A multitude of extracorporeal procedures have been introduced into intensive care medicine. Applied with adequate skills and experience, most of these techniques will suffice to replace excretory renal function. However, because of low efficacy arterio-venous procedures (CAVH and CAVHD) have been abandoned for the veno-venous, pump-driven techniques (CVVH and CVVHD). Up to now, there is no consensus whether continuous or intermittent renal replacement therapy is more advantageous. In many cases, oliguric patients with circulatory instability will be treated by CVVH, even though there is no prospective study to show that in terms of outcome continuous treatment is superior to intermittent hemodialysis. It is equally conceivable to treat such patients with daily, prolonged (intermittent) hemodialysis. Apparently, the dose of replacement therapy, be it continuous filtration (36 to 48 l/24 h) or intermittent hemodialysis (daily 3 to 4 h) with a target BUN of less than 50 mg/dl, is more important than the modality of treatment. Moreover, there is good evidence that the use of biocompatible membranes (no complement- or leukocyte activation) is preferable and that with high-volume hemofiltration bicarbonate-containing replacement fluids should be used. However, despite all the technical advances, we firmly believe that the skills and the experience of those physicians and nurses who actually perform renal replacement therapy in the ICU are more important than the modality of treatment applied.