 Subjects receiving CVVHD will receive a one gram dose of ertapenem. Serial blood samples over 24 hours will be taken to assess the ertapenem blood concentrations over time. Spent dialysate and urine samples if any will also be measured for ertapenem content to determine how much drug is removed by CVVHD and kidneys. A pharmacokinetic evaluation will be made to determine what is the most appropriate dose for this drug in patients receiving CVVHD to achieve pharmacokinetic and pharmacodynamic goals. 