title: Instant centre frequency at anaesthetic induction--a new way to analyse sympathovagal balance.
abstract: The instant centre frequency (ICF) of RR interval has been proposed as a global index to analyse the sympathovagal interaction in the heart. The aim of this study was to assess the ICF during anaesthesia to test if it can reliably capture the neural control of the cardiovascular system. Twenty-four ASA II or III patients scheduled for cardiac surgery were included in the study. They were allocated in two groups: control, no treatment (group 1, n = 12), and beta-adrenergic blockade by atenolol (group 2, n = 12). Spectra of pulse interval series were computed with a time-frequency method and they were divided into: very low frequency (VLF, 0.000-0.040 Hz), low frequency (LF, 0.050-0.150 Hz) and high frequency (HF, 0.160-0.500 Hz). Normalized power was obtained by dividing the cumulative power within each frequency band (LF or HF) by the sum of LF and HF; the ratio of LF/HF was also calculated. Instant centre frequency is a time-varying parameter that the evolution along time of the gravity centrum of a local spectrum. All spectral indexes were recorded at the following time points: before induction, after induction and before intubation, during intubation, and after intubation. The atenolol group had lower normalized LF and the LF/HF ratio (P < 0.05) higher HF before induction; and lower LF/HF ratio after induction and before intubation (P < 0.05). The ICF was higher in atenolol group at all times. The ICF shifted towards HF frequency after induction and before intubation and shifted towards LF during intubation in both groups. The autonomic nervous system control on the heart through the interaction of sympathetic and parasympathetic reflex mechanisms could be studied by the ICF. The ICF may assess the autonomic cardiac modulation and may provide useful information for anaesthetic management.
authors.affiliation: Laboratoire de Physiologie de l'Environment, Faculté de Médecine, Lyon Grange-Blanche and Hôpital Louis Pradel, IFR CV 39 and EA 1896, Lyon, France. edmundo@rockefeller.univ-lyon1.fr
authors.forename: Edmundo Pereira
authors.initials: EP
authors.lastname: de Souza Neto
authors.forename: Catherine
authors.initials: C
authors.lastname: Cerutti
authors.forename: Joseph
authors.initials: J
authors.lastname: Loufoua
authors.forename: Christine
authors.initials: C
authors.lastname: Saroul
authors.forename: Pascal
authors.initials: P
authors.lastname: Chiari
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Custaud
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Lehot
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000368:Aged; D018686:Anesthetics, Intravenous / Q000009:adverse effects; D001262:Atenolol / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D006348:Cardiac Surgical Procedures; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007442:Intubation, Intratracheal / Q000009:adverse effects; D007828:Laryngoscopy / Q000009:adverse effects; D008297:Male; D008874:Midazolam / Q000009:adverse effects; D008875:Middle Aged; D011674:Pulse; D017409:Sufentanil / Q000009:adverse effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D013997:Time Factors; D014630:Vagus Nerve / Q000187:drug effects* / Q000503:physiopathology
chemical_list: D000319:Adrenergic beta-Antagonists; D018686:Anesthetics, Intravenous; D001262:Atenolol; D017409:Sufentanil; D008874:Midazolam