Abnormal shock index exposure and clinical outcomes among critically ill patients: A retrospective cohort analysis

PURPOSE: To assess the predictive value of a single abnormal shock index reading (SI ≥0.9; heart rate/systolic blood pressure [SBP]) for mortality, and association between cumulative abnormal SI exposure and mortality/morbidity. MATERIALS AND METHODS: Cohort comprised of adult patients with an intensive care unit (ICU) stay ≥24-h (years 2010-2018). SI ≥0.9 exposure was evaluated via cumulative minutes or time-weighted average; SBP ≤100-mmHg was analyzed. Outcomes were in-hospital mortality, acute kidney injury (AKI), and myocardial injury. RESULTS: 18,197 patients from 82 hospitals were analyzed. Any single SI ≥0.9 within the ICU predicted mortality with 90.8% sensitivity and 36.8% specificity. Every 0.1-unit increase in maximum-SI during the first 24-h increased the odds of mortality by 4.8% [95%CI; 2.6-7.0%; p < .001]. Every 4-h exposure to SI ≥0.9 increased the odds of death by 5.8% [95%CI; 4.6-7.0%; p < .001], AKI by 4.3% [95%CI; 3.7-4.9%; p < .001] and myocardial injury by 2.1% [95%CI; 1.2-3.1%; p < .001]. ≥2-h exposure to SBP ≤100-mmHg was significantly associated with mortality. CONCLUSIONS: A single SI reading ≥0.9 is a poor predictor of mortality; cumulative SI exposure is associated with greater risk of mortality/morbidity. The associations with in-hospital mortality were comparable for SI ≥0.9 or SBP ≤100-mmHg exposure. Dynamic interactions between hemodynamic variables need further evaluation among critically ill patients.