A new analytical method for determining beta-lactam antibiotic concentrations in the blood of intensive care patients is to be evaluated. Patients receive antibiotic therapy with beta-lactam antibiotics in the general surgery intensive care unit. Blood samples are collected daily for routine clinical testing; a portion of these samples is used for the new method. The antibiotic levels, routinely measured using the gold standard, are documented and used as a reference point. The goal of the study is to establish a rapid and cost-effective method for determining beta-lactam antibiotic levels, which will subsequently enable rapid dose adjustment.