AbstractBackgroundOur aim in this retrospective cohort study was to assess the impact on mortality of the empirical use of polymyxin as therapy for carbapenem-resistant gram-negative bacteria (CR-GNB) in septic patients. The study was performed at a tertiary academic hospital in Brazil, from January 2018 to January 2020, the pre–coronavirus disease 2019 period.MethodsWe included 203 patients with suspected sepsis. The first doses of antibiotics were prescribed from a “sepsis antibiotic kit”, which contained a selection of drugs, including polymyxin, with no preapproval policy. We developed a logistic regression model to assess risk factors associated with 14-day crude mortality. Propensity score for polymyxin was used to control biases.ResultsSeventy (34%) of 203 patients had infections with at least 1 multidrug-resistant organism isolated from any clinical culture. Polymyxins in monotherapy or in combination therapy were prescribed to 140 of the 203 (69%) patients. The overall 14-day mortality rate was 30%. The 14-day crude mortality was associated with age (adjusted odds ratio [aOR], 1.03; 95% confidence interval [CI], 1.01–1.05;P= .01), SOFA (sepsis-related organ failure assessment) score value (aOR, 1.2; 95% CI, 1.09–1.32;P< .001), CR-GNB infection (aOR, 3.94; 95% CI, 1.53–10.14;P= .005), and time between suspected sepsis and antibiotic administration (aOR, 0.73; 95% CI, .65–.83;P< .001). The empirical use of polymyxins was not associated with decreased crude mortality (aOR, 0.71; 95% CI, .29–1.71;P= .44).ConclusionsEmpirical use of polymyxin for septic patients in a setting with high CR-GNB prevalence was not associated with decreased crude mortality.