Vasoactive-Adjusted Shock Index for Risk Stratification in Adult Sepsis

INTRODUCTION: The vasoactive-adjusted shock index (VASI) has been shown to identify a refractory shock phenotype in pediatric sepsis that is associated with high mortality. However, its prognostic value remains unclear in adults. METHODS: In this retrospective cohort study, group-based trajectory modeling was applied to identify VASI trajectories. Cox regression estimated mortality risk across trajectory groups. Heterogeneity of treatment effect was assessed via covariate balancing propensity scores targeting the average treatment effect on the treated, with interaction terms tested in weighted logistic models. RESULTS: A total of 63853 patients was included. The VASI predicted ICU mortality significantly better than the shock index and provided incremental value beyond SOFA. Two distinct VASI trajectories were identified, with low VASI trajectory that remained consistently low and high VASI trajectory characterized by an early transient rise followed by a sustained decline. The high VASI group had markedly higher 28-day mortality (HR 2.89, 95% CI 2.72-3.08) and 90-day mortality (HR 2.85, 95% CI 2.68-3.03). Hydrocortisone treatment was associated with mortality in both groups, with no significant interaction. Albumin showed a protective effect only in the low VASI group (OR 0.667, 95% CI 0.545-0.816), but the interaction was not significant. CONCLUSION: The early trajectory of VASI identifies a high-risk clinical phenotype in adult sepsis that is strongly associated with poor outcomes. However, no significant heterogeneity of treatment effect was observed for hydrocortisone or albumin in different VASI trajectories.