Injury severity-based discrepancies in severe trauma survival improvement

Current trauma outcome reporting via registries captures nearly all trauma patients at risk of death. Most of these patients have milder injuries and they considerably outnumber the most critically injured patients. A change in outcomes of the whole group, may not be shared equally among all patients. Change or stasis in outcomes of the most severely injured could be masked by this bulk of more mildly injured trauma patients. We sought to examine the contemporary trends at reducing in-hospital mortality at highest injury severity patient group and hypothesized that mortality improvements are similar to all trauma patients included in a state trauma registry.

All patients with an Injury Severity Score of 13-75 in a state of 8 million people, were included over a 10-year period ending in December 2021. Patients, and their demographic, injury severity, and outcome data were retrieved from the state's trauma registry. Data were analysed using multiple logistic regression, dividing injury severity groups into the registry reported ISS ranges of 13-39 and 40-75, and the 40-75 group further divided into 40-49, 50-94, and 75.

27,862 patients who were admitted into the seven level 1 trauma centres of the state met inclusion criteria. The in-hospital mortality significantly decreased over the study period [OR: 0.976 (95%CI: 0.962-0.990)]. The ISS40-75 [n = 1,111 (4%)] patients' mortality did not change during this decade [OR: 1.005 (95%CI: 0.963-1.049)]. On subgroup analysis, the ISS40-49 had worsening mortality [OR: 1.079 (95%CI: 1.012-1.150)], the ISS50-74 group's mortality improved [OR: 0.913 (95%CI: 0.850-0.980)] and ISS75 group had no change [OR: 1.049 (95%CI: 0.878-1.252)].

The overall improvement in severely injured patients' mortality does not translate to the most critically injured ones. Further to this, the highest injury severity patients are not a homogenous group based on mortality improvement. Our analysis has identified the ISS 40-49 population for targeted quality improvement.