title: Initial fractal exponent of heart rate variability is associated with success of early resuscitation in patients with severe sepsis or septic shock: a prospective cohort study.
abstract: BACKGROUND
  Heart rate variability (HRV) reflects autonomic nervous system tone as well as the overall health of the baroreflex system. We hypothesized that loss of complexity in HRV upon intensive care unit (ICU) admission would be associated with unsuccessful early resuscitation of sepsis.
  
  
  METHODS
  We prospectively enrolled patients admitted to ICUs with severe sepsis or septic shock from 2009 to 2011. We studied 30 minutes of electrocardiogram, sampled at 500 Hz, at ICU admission and calculated heart rate complexity via detrended fluctuation analysis. Primary outcome was vasopressor independence at 24 hours after ICU admission. Secondary outcome was 28-day mortality.
  
  
  RESULTS
  We studied 48 patients, of whom 60% were vasopressor independent at 24 hours. Five (10%) died within 28 days. The ratio of fractal alpha parameters was associated with both vasopressor independence and 28-day mortality (P = .04) after controlling for mean heart rate. In the optimal model, Sequential Organ Failure Assessment score and the long-term fractal α parameter were associated with vasopressor independence.
  
  
  CONCLUSIONS
  Loss of complexity in HRV is associated with worse outcome early in severe sepsis and septic shock. Further work should evaluate whether complexity of HRV could guide treatment in sepsis.
authors: Pulmonary and Critical Care Medicine, Intermountain Medical Center, Murray, UT; Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City, UT. Electronic address: Samuel.Brown@imail.org.
authors: Samuel M
authors: SM
authors: Brown
authors: Quinn
authors: Q
authors: Tate
authors: Jason P
authors: JP
authors: Jones
authors: Daniel B
authors: DB
authors: Knox
authors: Kathryn G
authors: KG
authors: Kuttler
authors: Michael
authors: M
authors: Lanspa
authors: Matthew T
authors: MT
authors: Rondina
authors: Colin K
authors: CK
authors: Grissom
authors: Subhasis
authors: S
authors: Behera
authors: V J
authors: VJ
authors: Mathews
authors: Alan
authors: A
authors: Morris
mesh_terms: D018806:APACHE; D000328:Adult; D001499:Bayes Theorem; D004562:Electrocardiography; D005260:Female; D017709:Fractals; D006339:Heart Rate / Q000502:physiology*; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012151:Resuscitation / Q000379:methods*; D018805:Sepsis / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy*; D012772:Shock, Septic / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D015996:Survival Rate; D016896:Treatment Outcome; D014589:Utah / Q000453:epidemiology; D014662:Vasoconstrictor Agents / Q000008:administration & dosage
chemical_list: D014662:Vasoconstrictor Agents
keywords: Heart rate variability; Physiological variability; Sepsis; Shock
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