Timing, dose and mode of dialysis in acute kidney injury

In the past 3 years substantial progress has been made in the field of renal replacement therapy (RRT) for critically ill patients.

Two important multicenter randomized clinical trials have been recently published and extensively discussed: the randomized evaluation of normal versus augmented level (RENAL) replacement therapy study and the VA/NIH Acute Renal Failure Trial Network (ATN) study. The RENAL and ATN studies were designed to compare 'normal' or 'less intensive' renal support to an 'augmented' or 'intensive' therapy: both studies showed no benefit in outcomes by increases in intensity of RRT dose. The definition of 'normal dose' is now recommended in a range of 20-30 ml/kg per h for continuous therapies and/or thrice weekly intermittent hemodialysis. On the contrary, the complex issue of RRT optimal timing still remains uncertain and controversial.

Wide variations in clinical practice still require RRT for critically ill patients to be optimized. The ideal prescription does not exist; however, continuous hemofiltration at a dose of 30 ml/kg/h meets many requirements of optimal care. In order to shed some light in the issue of RRT timing, furthermore, in the near future a standardized and clinically relevant definition of 'early' RRT should be provided. Great expectations currently rely on the utilization of acute kidney injury severity classifications and on new biomarkers of renal function.