A randomised comparative crossover study to assess the affect on circuit life of varying pre-dilution volumes associated with Continuous Veno-Venous Haemofiltration (CVVH) and Continuous Veno-Venous Haemodiafiltration (CVVHDF).

Continuous Renal Replacement Therapy (CRRT) is an established treatment option in Australia for critically ill patients with severe Acute Renal Failure (ARF). Treatment efficiacy of CRRT is dependent on the continuous nature of the therapy to achieve azotemic control, normalisation of serum sodium, potassium and bicarbonate concentrations, and in the management of fluid volume. Due to the development of blood clots in the extracorporeal circuit the continuous nature of CRRT is interrupted. The aim of this research project is to evaluate the discontinuation of circuit life due to clotting between two widely used forms of CRRT. The impact of Continuous Veno-Venous Haemofiltration (CVVH) and Continuous Veno-Venous Haemodiafiltration (CVVHDF) will be investigated using a randomised crossover study design. Patients participating in the study will be intially randomised to receive either CVVH or CVVHDF and crossover to the other treatmenet modality only when each circuit has run its natural course. Provided the change of modality occurs sequentially and both circuits are taken down due to clotting, only one crossover between the two treatment modalities will be necessary. The patient will then resume CVVHDF in accordance with standard unit practice until CRRT is no longer required.