Prehospital shock index predicts outcomes after prolonged transport: A multicenter rural study

Abstract

Background: Shock index (SI) predicts outcomes after trauma. Prior single-center work demonstrated that emergency medical services (EMSs) initial SI was the most accurate predictor of hospital outcomes in a rural environment. This study aimed to evaluate the predictive ability of SI in multiple rural trauma systems with prolonged transport times to a definitive care facility.

Methods: This retrospective review was performed at four American College of Surgeons-verified level 1 trauma centers with large rural catchment basins. Adult trauma patients who were transferred and arrived >60 minutes from scene during 2018 were included. Patients who sustained blunt chest or abdominal trauma were analyzed. Subjects with missing data or severe head trauma (Abbreviated Injury Scale score, >2) were excluded. Poisson and binomial logistic regression were used to study the effect of SI and delta shock index (∆SI) on outcomes.

Results: After applying the criteria, 789 patients were considered for analysis (502 scene patients and 287 transfers). The mean Injury Severity Score was 8 (interquartile range, 6) for scene and 8.9 (interquartile range, 5) for transfers. Initial EMSs SI was a significant predictor of the need for blood transfusion and intensive care unit care in both scene and transferred patients. An increase in ∆SI was predictive of the need for operative intervention ( p < 0.05). There were increased odds for mortality for every 0.1 change in EMSs SI; those changes were not deemed significant among both scene and transfer patients ( p < 0.1).

Conclusion: Providers must maintain a high level of clinical suspicion for patients who had an initially elevated SI. Emergency medical services SI is a significant predictor for use of blood and intensive care unit care, as well as mortality for scene patients. This highlights the importance of SI and ∆SI in rural trauma care.

Level of evidence: Prognostic and Epidemiological; Level IV.

Figure 1.

Flow diagram of patients included in final analysis

Figure 2.

Effect plot demonstrating the expected total number of packed red blood cells (PRBC) transfused, and expected number of days in the intensive care unit (ICU) based on EMS shock index.