Establishing thresholds for shock index in children to identify major trauma.

Background: An abnormal shock index (SI) is associated with greater injury severity among children with trauma. We sought to empirically-derive age-adjusted SI cutpoints associated with major trauma in children, and to compare the accuracy of these cutpoints to existing criteria for pediatric SI.

Methods: We performed a retrospective cohort study using the 2021 National Trauma Data Bank (NTDB) Participant Use File. We included injured children (<18 years), excluding patients with traumatic arrests, mechanical ventilation upon hospital presentation, and inter-facility transfers. Our outcome was major trauma defined by the standardized triage assessment tool (STAT) criteria. Our exposure of interest was the SI. We empirically-derived upper and lower cutpoints for the SI using age-adjusted Z-scores. We compared the performance of these to the SI, pediatric-adjusted (SIPA), and the Pediatric SI (PSI). We validated the performance of the cutpoints in the 2019 NTDB.

Results: We included 64,326 and 64,316 children in the derivation and validation samples, of whom 4.9 % (derivation) and 4.0 % (validation) experienced major trauma. The empirically-derived age-adjusted SI cutpoints had a sensitivity of 43.2 % and a specificity of 79.4 % for major trauma in the validation sample. The sensitivity of the PSI for major trauma was 33.9 %, with a specificity of 90.7 % among children 1-17 years of age. The sensitivity of the SIPA was 37.4 %, with a specificity of 87.8 % among children 4-16 years of age. Evaluated using logistic regression, patients with an elevated age-adjusted SI had 3.97 greater odds (95 % confidence interval [CI] 3.63-4.33) of major trauma compared to those with a normal age-adjusted SI. Patients with a depressed SI had 1.55 greater odds (95 % CI 1.36-1.78) of major trauma. The area under the receiver operator characteristic curve (AUROC) for the empirically-derived model (0.62, 95 % CI 0.61-0.63) was similar to the AUROC for PSI (0.62, 95 % CI 0.61-0.63); both of which were greater than the SIPA model (0.58, 95 % CI 0.57-0.59).

Conclusion: Age-adjusted SI cutpoints demonstrated a mild gain in sensitivity compared to existing measures. However, our findings suggest that the SI alone has a limited role in the identification of major trauma in children.