Extracorporeal blood purification in the treatment of acute renal failure with multiorgan involvement.

It has been more than 35 years since the early use of dialytic techniques for the treatment of acute renal failure. Considering the survival of patients who would have clearly succumbed to renal failure, attempts were made to determine at what level of uremic toxicity it would be beneficial to offer dialysis on a prophylactic basis. Those early attempts at defining a preventive strategy seemed to provide an improved survival by limiting incidence and severity of hemorrhage and sepsis. Subsequently, measurable advances have been difficult to attain, and the prognosis of complicated acute renal failure remained dismally poor. More recently, continuous renal replacement techniques were developed to offer a more physiologic treatment to those patients who were the most critically ill and unstable. These treatments offered the potential for a better tolerated fluid removal and a more constant control of electrolyte and acid-base balance. Other potential advantages included the use of more biocompatible membranes and the convective mode of solute transfer with its inherently greater removal of larger molecular weight substances such as the vasodilatory and inflammatory cytokines. Another approach has been to use extracorporeal purification to lower the levels of endotoxin, a goal which can be accomplished by either standard plasma exchange or, more elegantly, the use of selective adsorption columns. Despite the promise of these methodologies, the lack of an acceptable grading system for the severity of critical illness has hampered investigators who have tried to prove the eventual advantage of one blood purification technique over another.