Acute renal failure. Extracorporeal treatment strategies

The mortality for acute renal failure remains to be high (around 50-70%) despite manifold improvements in terms of techniques and equipment for renal replacement therapies as well as patient monitoring and intensive care support. At present, it is not clear if the method chosen for renal replacement therapy, i.e. intermittent hemodialysis or continuous hemofiltration, might impact significantly on the outcome of these patients. Whilst earlier retrospective studies suggested that CVVH might result in better survival and renal recovery in acute patients, recent prospective studies were unable to confirm these findings. These studies were, however, not evenly randomised in terms of severity of illness or too small to produce conclusive results. In clinical routine CVVH is typically chosen for treating patients with hemodynamic instability and volume overload. If one decides to perform CVVH, however, a filtrate volume of at least 35 ml/kg body weight and hour should be used as this was shown to be associated with better survival as compared to smaller filtrate volumes. A second controversy exists to date whether the choice of the dialyzer membrane might be of significant relevance for the outcome of patients with acute renal failure. Earlier studies indicated that the use of biocompatible membranes in these patients may result in improved patient survival and renal recovery. More recently, however, these results could not be confirmed by larger randomized, prospective clinical studies. Thus, the choice of the dialyzer membrane should be based on individual assessment rather than treatment bias.