title: Delta entropy of heart rate variability along with deepening anesthesia.
abstract: BACKGROUND
  Conventional time and frequency domain measures of heart rate variability (HRV) are strongly influenced by anesthetic drugs, and are therefore not able to detect subtle changes in HRV, even during light anesthesia. Approximate entropy of R-R intervals is an HRV measure that has a tendency to decrease during anesthesia, but it is severely compromised by low-frequency variations of the signal. However, the negative effect of the low-frequency variations can be eliminated by differentiating the R-R interval tachogram before analysis. We designed this study to investigate characteristics of a novel HRV measure, named δ entropy (dEn), during deepening anesthesia.
  
  
  METHODS
  Eight healthy subjects were anesthetized with sevoflurane and 8 with propofol in a stepwise manner using 3 escalating concentrations (2%, 3%, and 4% end-tidal concentration and 7.4 ± 1.7, 12.3 ± 2.6, and 18.3 ± 5.0 μg/mL plasma concentration, respectively) at 30-minute intervals. A third group of 8 subjects received a supramaximal IV dose of glycopyrrolate without anesthesia to examine the effect of cardiac vagal activity on dEn. We computed dEn at baseline, during each step of anesthesia and during the anticholinergic blockade.
  
  
  RESULTS
  The dEn decreased along with deepening levels of sevoflurane and propofol anesthesia up to 33% (95% confidence interval [CI] 21%-44%) and 38% (95% CI 28%-48%), respectively. At each anesthesia level, dEn differed significantly (P < 0.05) from that measured at the preceding level, similarly in both the sevoflurane and propofol groups. Parasympathetic blockade by glycopyrrolate was found to decrease dEn by 17% (95% CI 6%-28%).
  
  
  CONCLUSIONS
  The dEn is a novel HRV measure able to detect subtle sympathetic- and parasympathetic-mediated alterations in HRV both during deepening levels of sevoflurane and propofol anesthesia and during exceedingly deep anesthesia.
authors.affiliation: Department of Anaesthesiology, Intensive Care, Emergency Care and Pain Medicine, Turku University Hospital, Hietalahdenkatu 1 a 5 FIN-65100 Vaasa, Finland. mika.eero.maenpaa@utu.f
authors.forename: Mika
authors.initials: M
authors.lastname: Mäenpää
authors.forename: Timo
authors.initials: T
authors.lastname: Laitio
authors.forename: Tom
authors.initials: T
authors.lastname: Kuusela
authors.forename: Jani
authors.initials: J
authors.lastname: Penttilä
authors.forename: Kaike
authors.initials: K
authors.lastname: Kaisti
authors.forename: Sargo
authors.initials: S
authors.lastname: Aalto
authors.forename: Susanna
authors.initials: S
authors.lastname: Hinkka-Yli-Salomäki
authors.forename: Harry
authors.initials: H
authors.lastname: Scheinin
mesh_terms: D000328:Adult; D000758:Anesthesia / Q000009:adverse effects; D003700:Delta Rhythm / Q000187:drug effects / Q000502:physiology*; D004562:Electrocardiography / Q000187:drug effects / Q000379:methods; D019277:Entropy; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000009:adverse effects; D016343:Monitoring, Intraoperative / Q000379:methods*; D015742:Propofol / Q000009:adverse effects; D000077149:Sevoflurane; D055815:Young Adult
chemical_list: D008738:Methyl Ethers; D000077149:Sevoflurane; D015742:Propofol