(536) Antimicrobial De-Escalation Practices in the Intensive Care Unit

Introduction: Initial empiric broad-spectrum antibiotics for sepsis should be followed by antimicrobial de-escalation (ADE) when possible, to minimize patient harm and the development of antimicrobial resistance. The primary objective of this study was to determine the proportion of patients who received ADE within 24 hours of definitive culture results.

Methods: This was a multicenter, retrospective cohort study conducted in the intensive care units (ICU) of 15 hospitals in Australia and New Zealand. Consecutive medical records of patients admitted to the ICU were evaluated. Adult patients were included if they were started on broad spectrum antibiotics (e.g., piperacillin/tazobactam) for suspected infection within 24h of ICU admission. ADE was defined as switching from a broad-spectrum agent to a narrower spectrum agent or drug cessation.

Results: There were 631 patients screened, of which 425 were included in the study. Patients had a mean age of 64 ± 16 years, 256 (60%) were male, 136 (32%) were mechanically ventilated, 83 (20%) were immunosuppressed, and the most common site of infection was respiratory (n=142, 33%). There were 269 (63%) patients who were eligible for ADE based on cultures in the ICU. Of these, ADE occurred within 24h of definitive culture in 140/269 (52%), occurred beyond 24h in 56/269 (21%), occurred but unable to determine if within 24h in 35/269 (13%), and did not occur at any time in the ICU in 38/269 (14%). In the subset where ADE within 24h of definitive culture could be determined and possible (n=234), it occurred in 84/126 (67%) with positive culture with susceptibilities, 19/32 (59%) with positive culture without susceptibility, and 37/76 (49%) with negative cultures.

Conclusions: Half of eligible patients received ADE within 24 hours of definitive culture results in the ICU. ADE is more likely to occur in patients with positive cultures with susceptibilities.