Effect of age on the interaction between heart rate and mortality in prehospital trauma care

Objectives: The association between tachycardia and age in prehospital trauma mortality has not been thoroughly studied. The purpose of this study was to evaluate the interaction effects of age between prehospital tachycardia and mortality in adult trauma patients.Methods: Adult trauma patients during 2012, 2013, and 2015 who were treated and transported by emergency medical services (EMS) were analyzed. Main exposure was tachycardia (>90 beat/min) measured at the scene. The primary outcome was mortality, the secondary outcome was worsened disability. Multivariable logistic regression with interaction models between tachycardia and age was used to calculate the adjusted odds ratio (AOR) with 95% confidence intervals after adjusting for confounders.Results: A total of 35,542 patients were analyzed. Tachycardia had a significant association with mortality and worsened disability: 1.41 (1.28–1.54) for mortality and 1.25 (1.15–1.36) for worsened disability. In the interaction analysis, the AOR for mortality by tachycardia in age over 84 years was insignificant: 1.2 (1.11–1.3) for 15–64 years, 1.4 (1.29–1.52) for 65–84 years, 1.14 (0.92–1.42) for age over 85 years, respectively (p < 0.01 for interactions).Conclusion: Tachycardia had a significant association with mortality and worsened disability in prehospital trauma patients and age over 85 years old had a significantly different interaction effect. Prehospital trauma care protocol should include recognizing severe cases based on the patient’s heart rate and age. It would be helpful in the decision-making at the scene such as trauma center transfer and advanced treatment.