Background: Evidence supporting the association between 1-hour bundle achievement and patient outcomes is limited and inconsistent. Hence, this study aimed to address the impact of 1-hour bundle achievement on outcomes in septic shock patients.Methods: A prospective multicentre observational study of septic shock patients with a protocolised resuscitation bundle therapy at emergency departments was conducted from October 2015 to December 2018. In-hospital mortality according to 1-hour bundle

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... ievement from shock recognition were compared using multivariable logistic regression analysis. Patients were also divided into six groups according to the time of bundle achievement and outcomes were compared to examine the difference in outcome for each group over time: group 1 (≤1 h; reference), 2 (1–2 h), 3 (2–3 h), 4 (3–4 h), 5 (4–5 h), and 6 (5–6 h). Results: In total, 1,612 patients with septic shock were included and in-hospital mortality was 18.2%. The 1-hour bundle was achieved in 461 (28.6%) patients. In multivariate analysis, the group achieving 1-hour bundle did not show a significant difference in in-hospital mortality compared to those who did not achieve 1-hour bundle (odds ratio = 0.74, confidence interval: 0.522–1.049, p = 0.091). However, groups 2, 3, 4, 5, and 6 showed significantly lower odds ratios of in-hospital mortality compared to those who did not achieve the bundle elements (odds ratio = 0.733, 0.604, 0.541, 0.532, and 0.458, respectively; p = 0.042, 0.001, < 0.001, 0.001, and < 0.001, respectively). There was no significant difference in in-hospital mortality over time for each group compared to that of group 1 used as a reference.Conclusion: One-hour bundle achievement was not associated with improved outcomes in septic shock patients with protocolised resuscitation bundle therapy. However, groups achieving 2-, 3-, 4-, 5-, and 6-hour bundle were associated more with improved outcome than those who did not. Further clinical trials are needed to clarify the clinical implications of 1-hour bundle achievement.