Association between early ICU fever burden and 28-day mortality in patients with acute ischemic stroke: a retrospective cohort study based on the MIMIC-IV database.

BACKGROUND: Fever is common during the acute phase of acute ischaemic stroke and has been associated with poor outcomes. However, single temperature values may not adequately capture the cumulative effect of sustained thermal exposure. This study evaluated the association between early ICU fever burden and 28-day all-cause mortality in patients with acute ischaemic stroke. METHODS: This retrospective cohort study used data from the MIMIC-IV database. Adult patients with acute ischaemic stroke admitted to the ICU for the first time were included. Fever burden was calculated during the first 72 h after ICU admission as the area under the temperature-time curve above 37.9 °C and was standardized to 24 h. Patients were classified into no, low and high fever-burden groups. The primary outcome was 28-day all-cause mortality from ICU admission. Cox proportional hazards models with multiple imputation were used for the primary analysis. Sensitivity analyses, inverse probability of treatment weighting and subgroup analyses were performed to assess the robustness of the findings. RESULTS: A total of 3,016 patients were included, of whom 2,229 had no fever burden, 394 had low fever burden and 393 had high fever burden. The 28-day mortality rates were 15.3, 28.7 and 36.6%, respectively. In the fully adjusted multiply imputed Cox model, low and high fever burden were associated with higher 28-day all-cause mortality compared with no fever burden, with adjusted HRs of 1.404 (95% CI 1.126-1.751) and 1.948 (95% CI 1.564-2.427), respectively. The association was generally supported by complete-case analysis, IPTW analysis, alternative exposure windows, landmark analyses, alternative temperature thresholds, adjustment for temperature measurement density and exclusion of patients with sepsis. CONCLUSION: In ICU patients with acute ischaemic stroke, greater fever burden during the first 72 h after ICU admission was associated with higher 28-day all-cause mortality. Early ICU fever burden may provide time-integrated prognostic information, but its clinical utility and therapeutic implications require further prospective validation.