Pharmacokinetics of Piperacillin/Tazobactam in Patients Treated by Continuous Renal Replacement Therapy

Inclusion Criteria: * 18 years of age and older . * Females of childbearing potential must have a negative pregnancy test at screening. * Subjects whose life expectancy is estimated over 7 days. * Anuric patients requiring continuous venovenous hemodiafiltration * Septic patients,severe sepsis or septic shock * Written informed consent should be given either by the patient or a member of his family Exclusion Criteria: * Subjects with a history of true allergy or adverse drug reactions * Pathogens whose antibiotic susceptibility is not proved. * Patients having impaired hepatic function * Contraindication of anticoagulation by heparin * Residual renal function * Participation in a clinical trial * Interruption of treatment by piper/tazo or hemodiafiltration during the study. * Patients with psychiatric disorder or serious medical condition which in the opinion of the investigator may lead to complexity in patient management.