Study to Evaluate the Safety and Efficacy of the Renal Assist Device in Patients With Acute Renal Failure

* The purpose of this study is to evaluate the safety and efficacy of the RAD to determine whether the RAD is effective in reducing mortality in patients with Acute Renal Failure due to Acute Tubule Necrosis and to evaluate the safety of the RAD * If the RAD works normally when used for as long as 72 hours * If the RAD will provide added benefits to normal CVVH therapy for patients with Acute Renal Failure