Combination of reverse shock index and simplified motor score as a strong discriminator of trauma outcomes

Background: The reverse shock index multiplied by simplified motor score (rSI-sMS) is a novel and rapid measure for assessing injury severity in patients with trauma in prehospital settings; however, its discriminant ability requires further validation. Methods: A retrospective cohort study was conducted from trauma database of Taipei Tzu Chi Hospital to compare the accuracy of the rSI-sMS with that of the shock index, modified shock index, reverse shock index multiplied by the Glasgow Coma Scale (rSI-GCS), and the reverse shock index multiplied by GCS motor subscale (rSI-GCSM) for discriminating in-hospital mortality, intensive care unit (ICU) admissions, prolonged ICU stays ≥14 days, and prolonged hospital stays ≥30 days in patients with trauma. Results: A total of 11,760 patients from the trauma database were included. rSI-sMS had significantly better accuracy in discriminating in-hospital mortality, ICU admissions, prolonged ICU stays (≥14 days), and prolonged hospital stays (≥30 days) than the shock index, modified shock index, and rSI-GCSM, whereas its accuracy was similar to that of the rSI-GCS. Furthermore, rSI-sMS had better accuracy for discriminating clinical outcomes in patients with an injury severity score (ISS) ≥16, motor vehicle collisions, falls, no chronic disease, and cardiovascular disease as well as in geriatric and nongeriatric patients. In patients with mixed and isolated brain injuries, rSI-sMS accurately discriminated the four clinical outcomes, similar to rSI-GCS. The optimal cutoff value of rSI-sMS had a discriminant ability of 85.0, 78.6, 75.2, and 81.0% for in-hospital mortality, ICU admissions, ICU stay ≥14 days, and hospital stays of ≥30 days, respectively. Conclusions: Compared with the shock index, modified shock index, and rSI-GCSM, rSI-sMS is a more accurate field triage scoring system for discriminating in-hospital mortality, ICU admissions, prolonged ICU stay, and prolonged hospital stays in patients with trauma.