Reverse shock index multiplied by Glasgow Coma Scale score (rSIG) is a simple measure with high discriminant ability for mortality risk in trauma patients: an analysis of the Japan Trauma Data Bank

Abstract

Background: The shock index (SI), defined as heart rate (HR) divided by systolic blood pressure (SBP), is reported to be a more sensitive marker of shock than traditional vital signs alone. In previous literature, use of the reverse shock index (rSI), taken as SBP divided by HR, is recommended instead of SI for hospital triage. Among traumatized patients aged > 55 years, SI multiplied by age (SIA) might provide better prediction of early post-injury mortality. Separately, the Glasgow Coma Scale (GCS) score has been shown to be a very strong predictor. When considering these points together, rSI multiplied by GCS score (rSIG) or rSIG divided by age (rSIG/A) could provide even better prediction of in-hospital mortality.

Methods: This retrospective, multicenter study used data from 168,517 patients registered in the Japan Trauma Data Bank for the period 2006-2015. We calculated areas under receiver operating characteristic curves (AUROCs) to measure the discriminant ability by comparing those of SI (or rSI), SIA, rSIG, and rSIG/A for in-hospital mortality and for 24-h blood transfusion.

Results: The highest ROC AUC (AUROC), 0.901(0.894-0.908) for in-hospital mortality in younger patients (aged < 55 years), was seen for rSIG. In older patients (aged ≥ 55 years), the AUROC of rSIG/A, 0.845(0.840-0.850), was highest for in-hospital mortality. However, the difference between rSIG and rSIG/A was slight and did not seem to be clinically important. rSIG also had the highest AUROC of 0.745 (0.741-749) for 24-h blood transfusion.

Conclusions: rSIG ((SBP/HR) × GCS score) is easy to calculate without the need for additional information, charts or equipment, and can be a more reliable triage tool for identifying risk levels in trauma patients.

Keywords: Glasgow Coma Scale score; Heart rate; In-hospital mortality; Japan Trauma Data Bank; Systolic blood pressure.

Fig. 1

Patients flow chart. JTDB, Japan Trauma Data Bank; HR, heart rate, SBP; GCS, Glasgow Coma Scale

Fig. 2

Comparisons of receiver operating characteristic (ROC) curves for in-hospital mortality. Bold line, shock index (SI); dashed line, SI × age (SIA); solid line, SI ÷ Glasgow Coma Scale (GCS) score (SI/G); dotted line, SIA ÷ GCS score (SIA/G)

Fig. 3

Comparison of receiver operating characteristic (ROC) curves for in-hospital mortality by age. Solid line, shock index ÷ Glasgow Coma Scale score (SI/G); dotted line, shock index × age ÷ Glasgow Coma Scale score (SIA/G). a ROC curves in younger patients (aged < 55 years). b ROC curves in older patients (aged ≥ 55 years). AUROC, area under the ROC

Fig. 4

Proportion of patients with in-hospital mortality by reverse shock index × Glasgow Coma Scale score (rSIG) and by rSIG ÷ age (rSIG/A). The y axis shows the outcome variable of the proportion of patients with in-hospital mortality. The x axis shows rSIG (a) or rSIG/A (b)

Fig. 5

Comparisons of receiver operating characteristic (ROC) curves for in-hospital mortality. The vertical axis shows sensitivity, and the horizontal axis shows 1-specificity. a ROCcurves in younger patients (aged < 55 years). Solid line, reverse shock index × Glasgow Coma Scale score (rSIG); dotted line, simplified regression model (SRM); dashed line, Glasgow Coma Scale, Age, and systolic blood pressure (GAP) score. b ROC curves in older patients (aged ≥ 55 years). Solid line, rSIG ÷ age (rSIG/A); dotted line, SRM; dashed line, GAP score