Continuous renal replacement therapy: continuous blood purification in the intensive care unit.

Severe acute renal failure (SARF) occurs when renal dysfunction is such that haemodialysis or haemofiltration becomes necessary to maintain homeostasis. SARF is increasingly seen in association with multiorgan failure and has become a predominantly Intensive Care Unit disorder. Because of this change in epidemiology, the treatment of SARF has evolved from being exclusively nephrologist and intermittent haemodialysis-based to being mostly intensivist and continuous haemofiltration-based, particularly in European countries with a strong ICU tradition and in Australia. Continuous renal replacement therapy (CRRT) has several advantages in critically ill patients, including greater flexibility, excellent haemodynamic tolerance, outstanding fluid balance control, excellent control of uraemia, prevention of cerebral oedema, ability to provide full and aggressive nutrition, and a possible anti-inflammatory effect. The blood purification effect of CRRT may, in fact, go beyond the simple control of uraemia. Several animal studies have now shown that CRRT attenuates the haemodynamic consequences of bacteraemia or endotoxaemia. Such studies have also shown that increasing the intensity of fluid exchange may offer further beneficial effects in the setting of sepsis. In the light of these findings, CRRT is moving into the area of adjuvant treatment of sepsis, and pilot randomized controlled trials are being conducted to test the hypothesis that CRRT, either in standard or high fluid exchange volumes, attenuates the inflammatory effects of sepsis in humans. In the future, the use of CRRT may extend beyond its initial scope into the area of adjuvant management of sepsis and continuous blood purification may become part of a complex multifaceted approach to multiorgan dysfunction.