MAP-Derived Shock Index for Point-of-Care Physiological Risk Stratification After CT-Confirmed Cervical Spine...

Background/Objectives: Early mortality risk stratification after CT-confirmed cervical spine fractures remains clinically challenging in patients with major trauma. Imaging establishes a structural diagnosis, but it does not fully capture early physiological deterioration. This study aimed to develop and internally validate a prognostic model for in-hospital mortality and evaluate whether a MAP-derived Shock Index provides incremental prognostic information beyond routinely available clinical variables and the Injury Severity Score (ISS). Methods: This retrospective single-center cohort study included 131 adults with CT-confirmed cervical spine fractures and ISS ≥ 15 who were admitted to a tertiary trauma center between 2013 and 2023. The MAP-derived Shock Index was calculated as heart rate divided by estimated systolic blood pressure, where estimated systolic blood pressure was defined a priori as 1.5 × MAP. Four prespecified logistic regression models were evaluated: a base clinical model, base plus MAP-derived Shock Index, base plus ISS, and base plus MAP-derived Shock Index plus ISS. Discrimination, Brier score, calibration, bootstrap internal validation, and decision curve analyses were performed. Results: The in-hospital mortality rate was 22.9% (30/131). The base plus MAP-derived Shock Index model achieved an apparent AUC of 0.93 and an optimism-corrected AUC of 0.91. The MAP-derived Shock Index provided incremental prognostic information beyond the ISS; as an individual predictor, its AUC was 0.82 compared with 0.74 for the ISS. With each 0.1-unit increase, the MAP-derived Shock Index was associated with higher odds of in-hospital mortality. Decision curve analysis suggested a higher apparent net benefit across clinically relevant thresholds. Conclusions: In this internally validated retrospective cohort, the MAP-derived Shock Index complemented clinical and ISS-based assessments for early in-hospital mortality risk stratification after CT-confirmed cervical spine fracture. The index is not the conventional SBP-based Shock Index, and the model requires external multicenter validation before clinical use.