Infections in critically ill patients are a major healthcare problem and an important source of morbidity and mortality. Since critically ill patients often have altered pharmacokinetics (PK) compared to non-critically ill patients there is a substantial risk that present standard dosing regimens of antibiotics lead to suboptimal outcomes for patients on the ICU or the ED. To prevent the risk of inadequate dosing in ICU patients, it is important to fully understand the PK of antibiotics in this vulnerable group in order to optimize the dosing regimens.

With this study, the investigators will describe the pharmacokinetics of cefuroxime and amikacin in ICU and ED patients. A heterogeneous population of ICU and ED patients will be included to be able to find which factors might influence the pharmacokinetics of these drugs and to what extent. By using population modeling the investigators will simulate different dosing regimens and MIC values and compare probability of target attainment between each of these dose and MIC combinations. This will allow the investigators to optimize dosing regimens of cefuroxime and amikacin in critically ill patients.

Inclusion Criteria:

1. The patient is admitted to the ICU or ED;
2. The patient is at least 18 years of age on the day of inclusion;
3. Is managed with a central venous catheter or arterial line;
4. Is treated with amikacin and/or cefuroxime as standard care.

Exclusion Criteria:

1. Has previously participated in this study.

Critically ill patients admitted to the ICU or ED.