Dosing of renal replacement therapy in acute kidney injury: lessons learned from clinical trials

Prescribing dialysis to manage acute kidney injury (AKI) is common and recently has become a controversial area for physicians. The concept of dialysis "dose" initially was developed for end-stage renal disease and has been extended to AKI in the last decade. Urea kinetic modeling has been the mainstay of dose quantification in end-stage renal disease. Extrapolation of these techniques to critically ill patients with AKI is difficult because of a non-steady state leading to a variable increase in urea generation rate, alterations in total-body water and its compartmental distribution, and changing renal excretory capacity. Additional challenges are imposed when dose is considered for different modalities of dialysis that vary in operational characteristics (diffusion, convection, and adsorption), duration (intermittent and continuous), and frequency. The purpose of this article is to review the concept of dialysis dose, perform a critical assessment of the most important clinical trials of dialysis dose in AKI, summarize clinical evidence from these trials, and define key research issues that should be addressed in the future.