The pharmacokinetics of antimicrobials is profoundly modified in Intensive care unit (ICU) patients. To adapt the treatment, it is recommended to measure blood levels of antibiotics. Some antibiotics, such as amikacin, are easy to monitor, while for other molecules, such as piperacillin/tazobactam, the drug monitoring is more difficult to obtain. These two molecules have similar physicochemical characteristics (hydrophilicity) and therefore have closed pharmacokinetic properties. OPTIMA is a study aiming at criteria will be used to judge whether the pharmacokinetic (PK) parameters of amikacin are predictive of those of piperacillin and tazobactam.

Inclusion Criteria:

• Patient ≥ 18 years old
• Patient hospitalized in the critical care department of the Lyon-Sud hospital centre
• Patient with a sepsis or a severe sepsis table defined by the latest international recommendations
• Patient to be treated by the amikacin + piperacillin/tazobactam association
• Patient affiliated to a social security system, having agreed to participate in the study

Exclusion Criteria:

• Patient with a known history of hypersensitivity or contraindication to amikacin, piperacillin or tazobactam
• Patient known to have previously received piperacillin/tazobactam or amikacin combination before inclusion
• Patient treated at the time of inclusion with dialysis techniques