title: Is heart rate variability better than routine vital signs for prehospital identification of major hemorrhage?
abstract: OBJECTIVE
  During initial assessment of trauma patients, metrics of heart rate variability (HRV) have been associated with high-risk clinical conditions. Yet, despite numerous studies, the potential of HRV to improve clinical outcomes remains unclear. Our objective was to evaluate whether HRV metrics provide additional diagnostic information, beyond routine vital signs, for making a specific clinical assessment: identification of hemorrhaging patients who receive packed red blood cell (PRBC) transfusion.
  
  
  METHODS
  Adult prehospital trauma patients were analyzed retrospectively, excluding those who lacked a complete set of reliable vital signs and a clean electrocardiogram for computation of HRV metrics. We also excluded patients who did not survive to admission. The primary outcome was hemorrhagic injury plus different PRBC transfusion volumes. We performed multivariate regression analysis using HRV metrics and routine vital signs to test the hypothesis that HRV metrics could improve the diagnosis of hemorrhagic injury plus PRBC transfusion vs routine vital signs alone.
  
  
  RESULTS
  As univariate predictors, HRV metrics in a data set of 402 subjects had comparable areas under receiver operating characteristic curves compared with routine vital signs. In multivariate regression models containing routine vital signs, HRV parameters were significant (P<.05) but yielded areas under receiver operating characteristic curves with minimal, nonsignificant improvements (+0.00 to +0.05).
  
  
  CONCLUSIONS
  A novel diagnostic test should improve diagnostic thinking and allow for better decision making in a significant fraction of cases. Our findings do not support that HRV metrics add value over routine vital signs in terms of prehospital identification of hemorrhaging patients who receive PRBC transfusion.
authors.affiliation: Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Materiel Command, Fort Detrick, MD 21702, USA.
authors.forename: Shwetha
authors.initials: S
authors.lastname: Edla
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Reisner
authors.affiliation: Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Materiel Command, Fort Detrick, MD 21702, USA.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Liu
authors.affiliation: US Army Institute of Surgical Research, Fort Sam Houston, TX 78234, USA.
authors.forename: Victor A
authors.initials: VA
authors.lastname: Convertino
authors.affiliation: US Army Institute of Surgical Research, Fort Sam Houston, TX 78234, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Carter
authors.affiliation: Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Materiel Command, Fort Detrick, MD 21702, USA. Electronic address: jaques.reifman.civ@mail.mil.
authors.forename: Jaques
authors.initials: J
authors.lastname: Reifman
mesh_terms: D000328:Adult; D004632:Emergency Medical Services / Q000379:methods*; D017707:Erythrocyte Transfusion; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006470:Hemorrhage / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D055986:Vital Signs / Q000502:physiology; D014947:Wounds and Injuries / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology