title: [Spectral analysis of the ECG R-R interval permits early detection of vagal responses to neurosurgical stimuli].
abstract: OBJECTIVE
  To assess the efficacy of ECG spectral analysis, compared with heart rate (HR) monitoring in the detection of vagal response to surgical stimuli.
  
  
  METHODS
  Twenty Asa II-III patients (age: 65 +/- 13 years) scheduled for surgery of cerebellopontine angle or implantation of sacral root stimulator were examined. Target controlled infusion of propofol (2-4 microg x ml(-1)) and remifentanil (4 ng x ml(-1)) was guided by the bispectral index (Bis). Arterial pressure via a radial catheter, pulse oximetry and end tidal CO2 were continuously monitored. Spectral analysis was achieved by connecting a computer to the cardiorespiratory monitor. Online power spectrum densities were calculated from the ECG R-R interval by software based on the fast Fourier transform (LabView, National Instruments, USA). Low frequency (LF: 0.04-0.15Hz) and high frequency (HF: 0.15-0.4Hz) were associated with sympathetic and parasympathetic activities respectively. We defined vagal reaction as a decrease in FC or an increase in HF >10% of the prestimuli value. HF and FC were compared according to the detection delay (by a Student t test with p < 0.05 considered significant) and a concordance test with a kappa coefficient (kappa): -1 = total discordance to 1 = total concordance.
  
  
  RESULTS
  Twelve vagal reactions (observed in 8 patients) were detected within 5.5 +/- 1.3 s (HF) and 12.4 +/- 1.6 (FC); p < 0.001. Concordance between the 2 parameters was 95% (kappa =0.9).
  
  
  CONCLUSIONS
  The ECG spectral analysis is a non-invasive technique, which permits the detection of intra-operative vagal reactions earlier than conventional monitoring of HR.
authors.affiliation: Département d'anesthésie-réanimation 3, service de neurochirurgie CHU Pellegrin, 33076, Bordeaux, France. musa.sesay@chu-bordeaux.fr <musa.sesay@chu-bordeaux.fr>
authors.forename: M
authors.initials: M
authors.lastname: Sesay
authors.forename: J R
authors.initials: JR
authors.lastname: Vignes
authors.forename: M
authors.initials: M
authors.lastname: Stöckle
authors.forename: M
authors.initials: M
authors.lastname: Mehsen
authors.forename: G
authors.initials: G
authors.lastname: Boulard
authors.forename: P
authors.initials: P
authors.lastname: Maurette
mesh_terms: D000368:Aged; D000758:Anesthesia; D002530:Cerebellopontine Angle / Q000601:surgery; D004599:Electric Stimulation Therapy; D004562:Electrocardiography; D004567:Electrodes, Implanted; D005260:Female; D005583:Fourier Analysis; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D019635:Neurosurgical Procedures; D010812:Physical Stimulation; D015656:Respiratory Mechanics / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*