Relationship between systolic blood pressure and mortality in older vs younger trauma patients – a retrospective multicentre observational study

BACKGROUND: The population of older trauma patients is increasing. Those patients have heterogeneous presentations and need senior-friendly triaging tools. Systolic blood pressure (SBP) is commonly used to assess injury severity, and some authors advocated adjusting SBP threshold for older patients. We aimed to describe and compare the relationship between mortality and SBP in older trauma patients and their younger counterparts. METHODS: We included patients admitted to three level-I trauma centres and performed logistic regressions with age and SBP to obtain mortality curves. Multivariable Logistic regressions were performed to measure the association between age and mortality at different SBP ranges. Subgroup analyses were conducted for major trauma and severe traumatic brain injury admissions. RESULTS: A total of 47,661 patients were included, among which 12.9% were aged 65–74 years and 27.3% were ≥ 75 years. Overall mortality rates were 3.9%, 8.1%, and 11.7% in the groups aged 16–64, 65–74, and ≥ 75 years, respectively. The relationship between prehospital SBP and mortality was nonlinear (U-shape), mortality increased with each 10 mmHg SBP decrement from 130 to 50 mmHg and each 10-mmHg increment from 150 to 220 mmHg across all age groups. Older patients were at higher odd for mortality in all ranges of SBP. The highest OR in patients aged 65–74 years was 3.67 [95% CI: 2.08–6.45] in the 90–99 mmHg SBP range and 7.92 [95% CI: 5.13–12.23] for those aged ≥ 75 years in the 100–109 mmHg SBP range. CONCLUSION: The relationship between SBP and mortality is nonlinear, regardless of trauma severity and age. Older age was associated with a higher odd of mortality at all SBP points. Future triage tools should therefore consider SBP as a continuous rather than a dichotomized predictor.