Daily haemodialysis in acute renal failure. Old wine in a new bottle?

Acute renal failure (ARF) is a frequent complication in hospitalized patients. Despite advances in intensive care and renal replacement therapy, outcomes in ARF are distressingly poor. The high mortality of critically ill patients with ARF relates at least in part to fatal non-renal organ complications of ARF itself. However, adequacy of dialysis therapy in the setting of ARF is still in its infancy. At present, neither for intermittent haemodialysis (IHD) nor continuous renal replacement therapies specifically designed techniques have been developed or validated to measure the delivered dose of in ARF. Furthermore targets of optimal or required dose have not been defined. Problems intrinsic to ARF that hinder accuracy of dialysis dose measurements utilizing urea kinetic modelling include a lack of urea eubolism, uncertainty about the true patient total water volume and volume of distribution of urea, and significant access recirculation. The difference in prescribed versus delivered dialysis dose in patients with ARF undergoing IHD may exceed 20% and more and the majority of ARF patients will receive dialysis doses less than 1.2, which is considered the minimal level for end-stage renal disease patients undergoing regular dialysis. Nonetheless retrospective data from the Cleveland Clinic clearly demonstrate an influence of delivered Kt/V urea on survival in patients with intermediate ICU ARF severity scores. Our group prospectively compared outcomes in patients with ARF receiving IHD daily or on alternate days. Daily HD was associated with fewer dialysis-related hypotensive episodes, a shorter time and smoother course to recovery of renal function and a significantly reduced mortality compared to conventional HD. This article highlights also the facts that patients in the conventional group (the standard treatment in North America) treated every other day for 3 to 5 hours have been inadequately dialyzed, having a mean blood urea nitrogen (BUN) of 104 mg/dl and significantly more respiratory failure, sepsis, gastrointestinal bleeding or changes in mental status. To avoid significant underdialysis, conventional estimates of total body water should be increased by a factor of 1.2. Strategies associated with improved outcomes that have emerged thus far in ARF should aim at a time-averaged BUN of less than 60 mg/dl with IHD. IHD should be prescribed in varying frequency if necessary with daily sessions in hypercatabolic oliguric or heavy weight critically ill patients.