Assessment of meropenem plasma concentration in critically ill patients who require CRRT (continuous renal replacement therapy). A standard dose of meropenem is administered, i.e. 1 gram every 8 hours.

This is a prospective observational study performed on critically ill patients. Inclusion criteria are a severe infection on admission requiring the use of meropenem and CRRT.

Both medical and surgical patients will be included. Any type of infections can be included (pulmonary, abdominal, urinary tract, etc.) Antibiotics regimen includes one-hour infusion of meropenem (1.0 gram) intravenously every 8 hours.

Blood samples (2 mL) will be collected at the 15, 30, 45, 60, 75, 90, 120, 180, 240, and 480 minutes after each dose of meropenem for 3 consecutive days. The standard arterial canula will be used to obtain samples.

30 minutes after each sample collection, blood will be centrifuged for 10 minutes at 3,000 rpms. Subsequently, supernatant will be collected and frozen.

Serum meropenem concentration will be measured by high-performance liquid chromatography.

Each patient's hemodynamic parameters will be recorded with the use of transpulmonary thermodilution technique (PICCO). Other therapies, i.e. ventilatory support, sedation, an antifungal agent will be given as required.

Inclusion Criteria:

• Patients who require ICU treatment due to severe infection
• age 18-80 years
• an eligible consent obtained from the patient or his/her attendant

Exclusion Criteria:

• allergy to meropenem
• lack of consent to participate in the study
• age of patients below 18 or above 80 years

Severely ill patients treated in ICU