Variation in antibiotic use across intensive care units in the Netherlands

Antibiotics are widely used in ICUs. This study aimed to examine ICU-level variation in antibiotic use across Dutch ICUs as a basis for quality improvement and antimicrobial stewardship efforts.

We conducted a retrospective observational study using routinely collected data from electronic health records and the National Intensive Care Evaluation Registry, including all admissions to 11 Dutch ICUs between 2016 and 2019. Systemic antibiotic use was measured using Defined Daily Doses (DDD), Days of Therapy (DOT), length of therapy, antibiotic free days, the Access, Watch, Reserve classification, and the Antibiotic Spectrum Index (ASI). Antibiotic use was assessed for three groups of ICU admissions: all admissions, those with pneumonia, and those with intra-abdominal sepsis. For the latter two groups, we quantified case-mix adjusted variation in DOT and ASI through indirect standardization and ICU fixed effect estimation.

Of the 51,205 ICU admissions, 73% received at least one antibiotic. Average antibiotic use was 88.9 DDD and 91.1 DOT per 100 patient-days in the overall ICU cohort. Pneumonia and intra-abdominal sepsis were diagnosed in 3059 and 1094 admissions, respectively. After case-mix adjustment, significant variation in DOT and ASI between ICUs remained for both the pneumonia and intra-abdominal sepsis groups. Some ICUs with low DOTs, indicating lower overall antibiotic use, had less favorable ASI scores, suggesting use of broader-spectrum antibiotics, while others showed the opposite pattern.

Antibiotic use varied significantly across ICUs, and case-mix did not explain these differences. The ASI provides important information in addition to the other antibiotic use metrics.