A pragmatic clinical definition of traumatic shock using systolic blood pressure and shock index: A national registry study

Background Traumatic shock (TS) is implicated in up to 40% of early trauma deaths; however, no consensus definition exists, and its epidemiology and outcomes have not been characterised at a population level in Australia. Aims To apply a pragmatic clinical definition of TS, based on systolic blood pressure (SBP) and shock index (SI), to a national trauma registry, and to describe the epidemiology and outcomes of major trauma (MT) patients with and without clinical signs of shock. Methods A retrospective cohort study was conducted using Australia New Zealand Trauma Registry (ANZTR) data (2017–2022). TS was defined as pre-hospital SBP ≤90mmHg or SI >1, or hospital arrival SBP ≤90mmHg or SI >1. Epidemiology and outcomes were compared with patients without these features. Outcomes were reported as absolute risk differences and risk ratios alongside odds ratios; analyses were unadjusted. Results Among 47,730 adult MT patients in the hospital arrival analysis, 16,463 (34.5%) were excluded from the pre-hospital analysis due to incomplete centre-level data. Patients with pre-hospital or hospital arrival signs of TS were younger, more severely injured, and more likely to sustain penetrating trauma. Clinical signs of shock were associated with substantially higher absolute in-hospital mortality: h-SBP ≤90mmHg, 30.9% versus 7.4% (ARD 23.5 percentage points, 95% CI 21.7–25.3; RR 4.2); h-SI >1, 19.2% versus 7.1% (ARD 12.1; RR 2.7); with similar findings pre-hospital. ED mortality differences, although associated with very large odds ratios, were small in absolute terms given the low baseline (h-SBP ≤90mmHg: ARD 5.6%, RR 25.0, OR 26.5). A stepwise relationship between decreasing hospital arrival SBP and mortality was observed across thresholds of ≤100, ≤90, and ≤80mmHg. Patients with shock also had higher rates of operative intervention and longer ICU and acute hospital lengths of stay. Conclusions A pragmatic clinical definition of TS using SBP and SI identified a major trauma subgroup with substantially higher mortality and resource use. Although unadjusted analyses limit causal inference, this descriptive study provides a foundation for future validation and prospective research, while highlighting important gaps in national trauma registry data quality.