Prospective Determination of Serum Ceftazidime Concentrations in Intensive Care Units

Introduction: The purpose of this study was to assess the value of a serum assay for ceftazidime (CAZ) in patients in the intensive care unit (ICU) of the Saint-Etienne University Teaching Hospital and in other ICUs in the region to optimize therapy. Material and Methods: Between November 1, 2005, and February 29, 2008, for patients hospitalized in ICUs not on dialysis and undergoing continuous CAZ infusion, serum assay of the antibiotic was performed 36 to 48 hours after the start of treatment using a single serum sample. The target serum CAZ concentration was 40 +/- 10 mg/L with a concentration/minimum inhibitory concentration ratio of 5 or greater x minimum inhibitory concentration of CAZ when a strain was isolated. Results: Serum CAZ concentration was determined in 92 patients (28 females, 64 males) receiving CAZ by continuous infusion. The mean age was 66 years (range, 19-89 years) and the mean weight was 73 kg (range, 33-122 kg). The CAZ dose was between 1 g and 6 g/24 hours. The mean serum CAZ concentration was 46.9 mg/L (range, 7.4-162.3 mg/L). Serum CAZ concentrations were as follows: 30 to 50 mg/L in 35.9% of patients, less than 30 mg/L in 36.9%, and greater than 50 mg/L in 27.2%. Infection was documented in 51 patients, with 42 strains of Pseudomonas aeruginosa being detected. The serum concentration/minimum inhibitory concentration ratio was 5 or greater for 84.3%. Antibiotic dosage was adjusted based on the CAZ assay results. Conclusion: Our study suggests that CAZ measurement is needed in ICUs to achieve adequate CAZ concentrations to avoid treatment toxicity and to achieve efficacy as rapidly as possible, particularly in strains having limited susceptibility to antibiotics.