Dose of dialysis in the intensive care unit: is the venom in the dose or in the clinical experience?

Many studies on the most 'adequate' dose of renal replacement therapy (RRT) in critically ill patients with acute kidney injury have obtained contradictory results. The previous issue of Critical Care reports a multi-centre study showing that a higher than conventional dose of RRT, whether continuous RRT or intermittent RRT, is not associated with better survival of these patients. This commentary highlights some of the problems associated with the interpretation of this and previously published studies. These problems include the use of targets of Kt/V urea or the ultrafiltration rate in millilitres per kilogram body weight, the latter quite difficult to estimate in these patients, the divergent co-morbidities of the patients, and the local experience of intensivists or nephrologists with either continuous RRT or intermittent RRT. The last factor could explain why some single centre studies did find an impact of dialysis dose on the survival of these patients whereas multi-centre studies did not.