title: Linear and nonlinear analysis of hemodynamic signals during sepsis and septic shock.
abstract: OBJECTIVE
  Neuroautonomic modulation of heart rate (HR) and blood pressure were assessed in sepsis or septic shock. We hypothesized that these metrics would be diminished in pediatric patients with sepsis and septic shock, indicating uncoupling of the autonomic and cardiovascular systems.
  
  
  METHODS
  Prospective case series.
  
  
  METHODS
  Pediatric intensive care unit in a tertiary care children's hospital.
  
  
  METHODS
  Thirty pediatric patients with sepsis or septic shock.
  
  
  METHODS
  None.
  
  
  RESULTS
  Metrics used included power spectral analysis, a linear frequency domain measure, and detrended fluctuation analysis, a nonlinear technique that assesses the degree of long-range correlation in HR or blood pressure. We found decreased low-frequency (2.68 +/- 0.24 vs. 3.37 +/- 0.17 [SEM] bpm2; p = .03) and high-frequency HR power (2.18 +/- 0.14 vs. 2.79 +/- 0.23 bpm2; p = .04) and increased detrended fluctuation analysis scaling exponent (1.22 +/- 0.06 vs. 1.00 +/- 0.07 bpm2; p = .02) in sepsis vs. shock patients, respectively. Compared with sepsis or shock, recovery was associated with increases in low-frequency (3.61 +/- 0.15 vs. 3.05 +/- 0.19 bpm2; p < .0001) and high-frequency HR power (3.11 +/- 0.15 vs. 2.50 +/- 0.22 bpm2; p < .0001).
  
  
  CONCLUSIONS
  We conclude that uncoupling of the autonomic and cardiovascular systems occurs over both short- and long-range time scales during sepsis, and the degree of uncoupling may help differentiate between sepsis, septic shock, and recovery states.
authors.affiliation: Department of Pediatrics, Oregon Health Sciences University, Portland, USA.
authors.forename: D
authors.initials: D
authors.lastname: Toweill
authors.forename: K
authors.initials: K
authors.lastname: Sonnenthal
authors.forename: B
authors.initials: B
authors.lastname: Kimberly
authors.forename: S
authors.initials: S
authors.lastname: Lai
authors.forename: B
authors.initials: B
authors.lastname: Goldstein
mesh_terms: D000293:Adolescent; D001794:Blood Pressure / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D011446:Prospective Studies; D018805:Sepsis / Q000503:physiopathology*; D012772:Shock, Septic / Q000503:physiopathology*