Shock and Trauma Risk Index Nomogram (STRIN): A bedside physiology-based tool for early-high-acuity care triage in...

Major trauma is a leading cause of mortality and permanent disability, especially in younger adults. Early identification of high-risk patients is critical for appropriate care. Tools like the Shock Index (SI) or New Trauma Score (NTS) enable rapid bedside assessment but show variable performance across populations.

To develop and internally test the Shock Trauma Risk Index Nomogram (STRIN), integrating Shock Index (SI), Glasgow Coma Scale (GCS), oxygen saturation (SpO₂), and mean arterial pressure (MAP) for early risk stratification of time-critical resource use in major trauma.

Data of a retrospective cohort (March 2022-December 2024) from a single level-1 centre retrieved from Lombardy registry was considered. Adult patients (≥16 years) with major trauma and complete vital signs were included. Composite outcome was emergency surgery (ES) within 6 h, massive transfusion (MT) (≥10 units of packed red blood cells within 24 h or ≥4 units within first hour), Intensive Care Unit (ICU) admission and interventional radiology procedures (IR). The model was developed using multivariable logistic regression with Restricted Cubic Splines. Performance was assessed through discrimination (AUROC), calibration (Hosmer-Lemeshow test, Brier score), and internal testing via bootstrap resampling. Comparative performance against SI and NTS included AUROC, Net Reclassification Improvement (NRI), Integrated Discrimination Improvement (IDI), and Decision Curve Analysis (DCA).

Among 611 patients, STRIN demonstrated superior discrimination (AUROC = 0.8441 [95% CI 0.813-0.875]) compared to SI (0.6979 [0.6566-0.7392]) and NTS (0.7582 [0.7212-0.7953]; p < 0.001 for both comparisons). STRIN showed satisfactory calibration (Hosmer-Lemeshow p = 0.096), lower Brier score (0.157), and minimal bias-corrected error (0.017). DCA revealed higher net benefit across clinically relevant thresholds. Compared to SI and NTS, STRIN achieved significant NRI (0.519 and 0.484, respectively) and IDI (0.179 and 0.107). Bootstrap testing confirmed model stability (optimism-corrected AUROC = 0.782; calibration slope = 0.98).

STRIN is a pragmatic, high-performing model for early risk stratification of time-critical interventions in major trauma. Leveraging four readily available physiological parameters, it offers a clinically actionable alternative to existing scores. External validation is ongoing across Lombardy; STRIN holds promise for integration into prehospital and emergency workflows to support timely, physiology-based decision-making in trauma care.