Renal replacement therapy in acute kidney injury: intermittent versus continuous? How much is enough?

Approximately 4% of all critically ill patients will require renal replacement therapy (RRT). Despite its potential reversibility, acute kidney injury has a significant impact on morbidity and mortality. Numerous studies have addressed the questions of modality choice and dose of RRT in the intensive care unit setting. There is no clear evidence that one renal replacement modality is superior to another. Two multicenter trials focusing on dialysis dose will probably be published in the next year, either confirming or invalidating the benefit of higher effluent rates. Another key aspect in the treatment of acute kidney injury is the consequence of RRT on long-term renal function. Although cohort studies have shown that continuous RRT shortens dialysis-dependence compared with intermittent hemodialysis, randomized trials and meta-analyses do not support these findings. Several unanswered questions, such as the timing of initiation and cessation of RRT, the modification of dialysis parameters over the course of acute kidney injury and the influence of fluid status need to be addressed in future trials in order to improve outcomes related to this condition.