title: Coefficient of Variation of Coarsely Sampled Heart Rate is Associated With Early Vasopressor Independence in Severe Sepsis and Septic Shock.
abstract: OBJECTIVE
  To determine whether variability of coarsely sampled heart rate and blood pressure early in the course of severe sepsis and septic shock predicts successful resuscitation, defined as vasopressor independence at 24 hours after admission.
  
  
  METHODS
  In an observational study of patients admitted with severe sepsis or septic shock from 2009 to 2011 to either of 2 intensive care units (ICUs) at a tertiary-care hospital, in whom blood pressure was measured via an arterial catheter, we sampled heart rate and blood pressure every 30 seconds over the first 6 hours of ICU admission and calculated the coefficient of variability of those measurements. Primary outcome was vasopressor independence at 24 hours; and secondary outcome was 28-day mortality.
  
  
  RESULTS
  We studied 165 patients, of which 97 (59%) achieved vasopressor independence at 24 hours. Overall, 28-day mortality was 15%. Significant predictors of vasopressor independence at 24 hours included the coefficient of variation of heart rate, age, Acute Physiology and Chronic Health Evaluation II, the number of increases in vasopressor dose, mean vasopressin dose, mean blood pressure, and time-pressure integral of mean blood pressure less than 60 mm Hg. Lower sampling frequencies (up to once every 5 minutes) did not affect the findings.
  
  
  CONCLUSIONS
  Increased variability of coarsely sampled heart rate was associated with vasopressor independence at 24 hours after controlling for possible confounders. Sampling frequencies of once in 5 minutes may be similar to once in 30 seconds.
authors.affiliation: Pulmonary and Critical Care, Intermountain Medical Center, Murray, UT, USA Pulmonary and Critical Care, University of Utah School of Medicine, Salt Lake City, UT, USA samuel.brown@imail.org.
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Brown
authors.affiliation: Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, USA.
authors.forename: M Quinn
authors.initials: MQ
authors.lastname: Tate
authors.affiliation: Research Division, Kaiser Permanente Southern California, Oakland, CA, USA.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Jones
authors.affiliation: Medical Informatics, Intermountain Healthcare, Murray, UT, USA.
authors.forename: Kathryn G
authors.initials: KG
authors.lastname: Kuttler
authors.affiliation: Pulmonary and Critical Care, Intermountain Medical Center, Murray, UT, USA Pulmonary and Critical Care, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lanspa
authors.affiliation: Internal Medicine, University of Utah Medical Center and School of Medicine, Salt Lake City, UT, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Rondina
authors.affiliation: Pulmonary and Critical Care, Intermountain Medical Center, Murray, UT, USA Pulmonary and Critical Care, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Colin K
authors.initials: CK
authors.lastname: Grissom
authors.affiliation: Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, USA.
authors.forename: V J
authors.initials: VJ
authors.lastname: Mathews
mesh_terms: D018806:APACHE; D000368:Aged; D001794:Blood Pressure; D003422:Critical Care; D005260:Female; D006339:Heart Rate; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D018805:Sepsis / Q000188:drug therapy / Q000503:physiopathology*; D012772:Shock, Septic / Q000188:drug therapy / Q000503:physiopathology*; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000627:therapeutic use
chemical_list: D014662:Vasoconstrictor Agents
keywords: hemodynamics; physiological variability; sepsis; shock; vasopressor agents