Elevated Modified Shock Index Within 24 Hours of ICU Admission Is an Early Indicator of Mortality in the Critically Ill.

PURPOSE

To assess whether exposure to modified shock index (MSI) in the first 24 hours of intensive care unit (ICU) admission is associated with increased in-hospital mortality.

METHODS

Adult critically ill patients were included in a case-control design with 1:2 matching. Cases (death) and controls (alive) were abstracted by a reviewer blinded to exposure status (MSI). Cases were matched to controls on 3 factors-age, end-stage renal disease, and ICU admission diagnosis.

RESULTS

Eighty-three cases and 159 controls were included. On univariate analysis, lorazepam administration (odds ratio [OR]: 5.75, confidence interval [CI] = 2.28-14.47; P ≤ .01), shock requiring vasopressors (OR: 3.62, CI = 1.77-7.40; P ≤ .01), maximum MSI (OR: 2.77 per unit, CI = 1.63-4.71; P ≤ .001), and elevated acute physiologic and chronic health evaluation (APACHE) III score at 1 hour (OR: 1.41 per 10 units, CI = 1.19-1.66; P ≤ .001) were associated with mortality. Maximum MSI (OR: 1.93 per unit, CI = 1.07-3.48, P = .03) and APACHE III score at 1 hour (OR: 1.29 per 10 units, CI = 1.09-1.53; P = .003) remained significant with mortality in the multivariate analysis. The optimal cutoff point for high MSI and mortality was 1.8.

CONCLUSION

Critically ill patients who demonstrate an elevated MSI within the first 24 hours of ICU admission have a significant mortality risk. Given that MSI is easily calculated at the bedside, clinicians may institute interventions earlier which could improve survival.