Renal replacement therapy for acute renal failure on the intensive care unit: coming of age?

The introduction and development of continuous renal replacement therapy (CRRT) represents one of the most substantial changes in patient management on the intensive care unit (ICU). Several issues, however, are still unresolved. Adequacy of dialysis in critically ill patients involves more than simple control of urea (although considered reflective of toxic uraemic compounds). It also concerns various (other) biochemical and clinical parameters. This article addresses important questions such as the different aspects of 'adequate' dialysis and its timing and intensity ('dialysis dosing'). Dialytic treatment should now be tailored to the patient, influenced by patient characteristics, urgency of treatment, haemodynamic tolerance and vascular access. For this, intermittent haemodialysis and CRRT should be regarded as complementary techniques, to be used interchangeably in critically ill patients with acute renal failure (ARF) according to circumstances. While awaiting scientific criteria for the initiation of renal replacement therapy in ARF patients, it seems reasonable to prefer prevention of physiological derangements to their post-hoc correction. This would mean early initiation of dialytic treatment as renal support rather than its initiation as renal replacement therapy for uraemic complications. The amount of dialysis ('dialysis dose') should preferably be prescribed on an individualised basis, especially when considering that the delivered dialysis dose may make a difference. Despite its limitations, simplified urea kinetic modelling, as outlined in this article's appendix, may be used as a bedside method to establish the required dose with CRRT. If not, at least the weight-adjusted ultrafiltration (UF) flow rate should be used as a surrogate for the prescribed dialysis dose (i.e., ml/kg/h). As the prescribed dialysis dose is usually less than the delivered dose, this should also be taken into account. In addition, nutrition should be viewed as an integral part of the dialysis prescription. Continuing effort should be made to develop 'evidence-based' guidelines for the appropriate prescription and delivery of renal replacement therapy to treat ARF in the ICU. This should include efforts to determine a validated dialysis dose methodology in ARF patients to address further the dose/outcome relationship. Based on existing data, some guidelines for the prescription and delivery of adequate (C)RRT are provided.