Bio-Shock Index: Proposal and Rationale for a New Predictive Tool for In-Hospital Mortality in Patients with Traumatic Brain Injury

We proposed a novel prognostic tool for the prediction of in-hospital mortality based on a combination of hemodynamic parameters and biomarkers in patients with traumatic brain injury (TBI). We hypothesized that a combination of shock index (SI) with high sensitive troponin T (HsTnT), the Bio-Shock Index (Bio-SI), has better prognostic power than its individual components.

A retrospective chart review was conducted (2011-2018) for patients with TBI. Patients were categorized into 2 groups (low and high Bio-SI) based on the receiver operating characteristic curve.

A total of 2619 patients were admitted with TBI, and 1471 fulfilled the inclusion criteria and 73% had high Bio-SI (≥10). High Bio-SI values were associated with more intraventricular hemorrhage (P = 0.001), brain edema (P = 0.001), and had lower mean arterial pressure (P = 0.001), admission Glasgow Coma Scale score (P = 0.001), and higher SI (P = 0.001), serum lactate (P = 0.001), HsTnT values (P = 0.001), and Rotterdam score (P = 0.03). Patients with high Bio-SI had a prolonged hospital (P = 0.003) and intensive care unit stay (P = 0.001); longer ventilatory days (P = 0.001) and had higher rates of pneumonia (P = 0.001), sepsis (P = 0.001), and in-hospital mortality (P = 0.001). The Bio-SI showed high sensitivity and negative predictive value (91.4% and 94.4%, respectively) as compared with elevated SI (50.2% and 87.6%, respectively) and positive troponin (79.7% and 93.7%, respectively).

The Bio-SI is potentially a better tool than its individual components to predict in-hospital mortality among patients with TBI; however, HsTnT alone outperforms SI. Prospective studies and multicenter trials studying troponin levels and SI in all patients with TBI with the inclusion of outcome scores will prove or disprove the predictability of the new index.