title: Heart rate variability is an independent predictor of morbidity and mortality in hemodynamically stable trauma patients.
abstract: BACKGROUND
  Reduced heart rate variability (HRV) reflects autonomic dysfunction and can triage patients better than routine trauma criteria or vital signs. However, there is questionable specificity and no consensus measurement technique. The purpose of this study was to analyze whether factors that alter autonomic function affect the specificity of HRV for assessing traumatic injury.
  
  
  METHODS
  We evaluated 216 hemodynamically stable adults (3:1 M:F; 97:3 blunt:penetrating; age 49 years ± 1 year, mean ± standard error) undergoing computed axial tomography (CT) scan to rule out traumatic brain injury (TBI). All were prospectively instrumented with a Mars Holter system (GE Healthcare, Milwaukee, WI). HRV was determined offline using time domain (standard deviation of normal-normal intervals, root-mean-square successive difference) and frequency domain (very low frequency [VLF], LF, wideband frequency, high frequency [HF], low to HF index ratio) calculations from 15-minute electrocardiogram and correlated with routine vital signs, mortality, TBI, morbidity, length of stay (LOS), and comorbidities. Significance (p ≤ 0.05) was determined using nonparametric analysis, Student's t test, analysis of variance, or multiple logistic regression.
  
  
  RESULTS
  VLF alone predicted survival, severity of TBI, intensive care unit LOS, and hospital LOS (all p < 0.05). Beta-blockers or diabetes had no effect, whereas age, sedation, mechanical ventilation, spinal cord injury, and intoxication influenced one or more of the variables with age being the most powerful confounder (all p < 0.05). Except for the Glasgow Coma Scale, no other routine trauma or hemodynamic criteria correlated with any of these outcomes.
  
  
  CONCLUSIONS
  Decreased VLF is an independent predictor of mortality and morbidity in hemodynamically stable trauma patients. Other time and other frequency domain variables correlated with some, but not all, outcomes. All were heavily influenced by factors that alter autonomic function, especially patient age.
authors.affiliation: Dewitt-Daughtry Family Department of Surgery, University of Miami Miller School of Medicine, Miami, Florida 33136, USA.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Ryan
authors.forename: Michael P
authors.initials: MP
authors.lastname: Ogilvie
authors.forename: Bruno M T
authors.initials: BM
authors.lastname: Pereira
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Gomez-Rodriguez
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Manning
authors.forename: Paola A
authors.initials: PA
authors.lastname: Vargas
authors.forename: Robert C
authors.initials: RC
authors.lastname: Duncan
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Proctor
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001930:Brain Injuries / Q000000981:diagnostic imaging; D016009:Chi-Square Distribution; D015897:Comorbidity; D004562:Electrocardiography; D005260:Female; D015600:Glasgow Coma Scale; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D015601:Injury Severity Score; D007902:Length of Stay / Q000706:statistics & numerical data; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012307:Risk Factors; D015996:Survival Rate; D014057:Tomography, X-Ray Computed; D014218:Triage; D014947:Wounds and Injuries / Q000401:mortality* / Q000503:physiopathology*