Does renal replacement therapy increase mortality in the ICU?

potential risks such as hypotension, catheter-related complications, hemorrhage and blood–extracorporeal circuit interactions. Several studies, however, have shown that early RRT in acute kidney injury (AKI) is associated with a better outcome in intensive care unit (ICU) patients [1-3]. A recent retrospective study published in Critical Care has questioned the use of RRT in critically ill patients, including those with severe AKI [4]. Compared with conservative treatment, RRT patients showed a higher mortality. Th e indication for RRT was at the discretion of the physician, and patients receiving RRT presented higher severity and renal impairment scores. After multivariate analysis correcting for severity of illness (Acute Physiology and Acute Chronic Health Evaluation II score and Sequential Organ Failure Assessment score), mor tality remained higher in RRT patients. In a multivariate analysis in septic shock patients, however, we observed that both severity scores are not related to mortality, contrary to the maximum Sequential Organ Failure Assessment score [5]. Th e decision of starting RRT in many patients during their ICU stay may have been related to evolving factors not included in the analysis (worsening severity, overload, progressing hypoxemia, and so forth), which aff ect mortality but are not detected in the initial snapshot assessment. For instance, it is inconceivable that anuric patients did not receive RRT. On the other hand, the use of RRT in some patients with mild renal impairment may have increased morbidity. Th e study underlines the idea that RRT is not necessary in many patients presenting mild AKI in the ICU, but may be misleading if we accept that this therapy is deleterious in general.