Vasopressor Dosing Trajectories in Septic Shock According to Initial Antimicrobial Susceptibility and Infection Source Concordance: A Retrospective Observational Study

Background/Objectives: Septic shock carries high mortality. Although guidelines recommend early empiric antibiotics, early identification of the infection source and selection of appropriate initial antibiotic therapy remain challenging. This study examined whether vasopressor trajectories, quantified as norepinephrine equivalent (NEE), differed according to initial antimicrobial susceptibility and concordance between presumed and final infection sources. Methods: This single-center retrospective observational study included adults with Sepsis-3 septic shock admitted to the intensive care unit between 2017 and 2023. Patients were classified into the appropriate-management group when the initial antibiotic therapy covered the subsequently identified causative pathogen and the initially presumed infection source was concordant with the final infection source; all others were classified into the inappropriate-management group. Primary outcomes were Max NEE duration and the times from Max NEE to 75%, 50%, 25%, and discontinuation of NEE. Results: Among 132 patients analyzed, 101 were classified into the appropriate-management group and 31 into the inappropriate-management group. Max NEE duration was shorter in the appropriate-management group (median (IQR), 4 (2–7) h vs. 6 (3–20) h; p = 0.0100) and remained shorter after excluding deaths during the Max NEE period (n = 119; 6 (2–11) h vs. 11 (5–14) h; p = 0.0314). Time to NEE reduction from Max NEE was shorter in the appropriate-management group, with significant differences at 75% (7 (4–13) h vs. 13 (9–23) h; p = 0.0066) and 25% (19 (13–29) h vs. 31 (16–46) h; p = 0.0247). Conclusions: Prolonged Max NEE duration and delayed NEE reduction were associated with inadequate coverage by initial antibiotic therapy or discordant infection source identification in this selected cohort. Vasopressor trajectories may help prompt reassessment of antibiotic therapy and infection source evaluation.