Early Arterial pH Changes as Strong Predictors of Mortality in Sepsis: A Multicenter Cohort Study.

Purpose

To evaluate the prognostic significance of early arterial pH changes (ΔpH) during the transition from the emergency department (ED) to the intensive care unit (ICU) in patients with sepsis.

Methods

This multicenter retrospective cohort study included 3,512 patients with community-acquired sepsis admitted to the ICU within 6 h of ED presentation between September 2019 and December 2023. The patients were stratified by baseline pH into acidosis (<7.35), normal (7.35-7.45), and alkalosis (>7.45). ΔpH was defined as the difference between ED pH and the lowest ICU pH within 24 h after ICU admission. The association between ΔpH and 28-day mortality was examined using multivariable Cox models with restricted cubic splines. Prognostic cutoffs were derived in a derivation cohort (70%) and validated in an independent cohort (30%).

Findings

ΔpH showed a nonlinear association with mortality, with greater absolute deviations, particularly negative ΔpH linked to increased risk. The optimal cutoffs differed by baseline status (-0.012 for acidosis, -0.145 for normal, and -0.240 for alkalosis). In the validation cohort, ΔpH values below these thresholds consistently predicted higher 28-day mortality, with adjusted hazard ratios (HRs): overall (HR, 2.80; 95% confidence intervals (CI), 2.13-3.69; C = 0.678), acidosis (HR, 2.71; 95% CI, 1.66-4.43), normal (HR, 4.43; 95% CI, 2.81-7.00), and alkalosis (HR, 1.90; 95% CI, 1.04-3.48).

Conclusions

Early arterial pH changes during the ED-to-ICU transition independently predicted mortality across baseline acid-base categories, particularly among patients with normal baseline pH. This highlights ΔpH as an early marker of acute deterioration in seemingly stable patients.