Approximately 300 patients have to be enrolled in the study. They are followed up until the end of ICU stay. Usually in clinical routine, patients suspected to have infection and simultaneously renal dysfunction making CVVHDF necessary. After enrolment blood and dialysate specimens are drawn and sent for analysis on specific time points. The analysis results are sent back to the study team at the Charité - Universitätsmedizin Berlin and enable them to optimize antiinfectiva treatment of the study patients.

Data are used to test calculation tools and modify them if necessary.

Little data exist whether desired and necessary blood levels of antiinfective drugs are reached during renal replacement therapy. Drug producing companies are not able to come forward with appropriate dosing recommendation in patients needing renal replacement therapy.

To achieve our study goal we plan:

1. To measure serum-concentrations of antiinfective drugs applied to the patients
2. To measure concentrations of antiinfective drugs in hemofiltration fluids.
3. To compare the actual measured concentrations with concentration predicted in known calculation tools.
4. To modify these calculation tools if necessary for better prediction.

Inclusion Criteria:

• Male and female patients, age ≥ 18 years
• Patients in the intensive care unit (ICU), needing renal replacement therapy due to renal dysfunction and are treated with antiinfective drugs

Exclusion Criteria:

• Pregnancy and lactation period.
• Participation in a clinical intervention study
• Lacking willingness to save and hand out data within the study
• Accommodation in an institution due to an official or judicial order
• The informed consent of the patient or the subject's legally acceptable representative can´t be obtained in time
• Patient has a power of attorney or patient's provision, where he/she refuses participation in any clinical trial

Critical ill patients