Continuous renal replacement therapy in critically ill patients.

Acute renal failure is an evolving syndrome in which new pathogenetic mechanisms have recently been elucidated. The evolution of the field of haemodialysis has led to a parallel development in the therapeutic approach to patients suffering from this syndrome. In particular, acute renal failure is more frequently seen as part of a more complex syndrome, defined as multiple organ failure. In this clinical setting, patients are almost inevitably confined to intensive care units and sepsis is a frequent underlying mechanism of organ failure. The use of new devices and new machines, together with a better understanding of the underlying mechanisms of solute and water removal, have allowed us to achieve higher levels of efficiency and clinical tolerance during artificial renal replacement therapy. The first objective has been reached by increasing the automation of the extracorporeal circuits and the operational levels of the different techniques; the second has been achieved by means of a new generation of monitoring techniques and new machines equipped with specific interfaces and alarms. This progress has made continuous forms of renal replacement (CRRT) possible and easy to perform without major problems or complications. The most promising and effective options for treating acute renal failure in critically ill patients are today offered by continuous renal replacement therapies. Classic indications, but also alternative non-renal indications, have been proposed for these techniques. The most advanced indication is the multiple organ dysfunction occurring in septic patients. The possible removal of proinflammatory mediators may permit a blockade of the systemic inflammation, a modulation of the altered immune response in these patients, and it may lead to a partial or total restoration of the lost homeostasis.