title: Sympathovagal effects of spinal anesthesia assessed by the spontaneous cardiac baroreflex.
abstract: BACKGROUND
  The changes in sympathovagal balance induced by spinal anesthesia remain controversial. The spontaneous baroreflex method allows the continuous assessment of the spontaneous engagement of the cardiac baroreflex, giving an index of sympathovagal balance. The purpose of this study was to follow the effects of spinal anesthesia on spontaneous baroreflex sensitivity.
  
  
  METHODS
  Continuous electrocardiogram and noninvasive blood pressure were recorded in 24 patients scheduled for elective inguinal hernia repair and randomly assigned to three groups: (1) no volume loading, (2) volume loading of 15 ml/kg lactated Ringer's solution, and (3) continuous infusion of etilefrine (an ephedrine-like drug). Each patient was studied before, during, and after bupivacaine-induced spinal anesthesia (mean sensory block: T4). Spontaneous baroreflex sensitivity and parameters of time-domain analysis of heart rate variability were calculated from 30 min of recording of each period.
  
  
  RESULTS
  No significant change in spontaneous baroreflex slope or parameters of time-domain analysis were observed after regional anesthesia in any group. However, three patients experienced episodes of bradycardia and hypotension in the absence of a high block; these three patients showed an increase in spontaneous baroreflex sensitivity and time-domain parameters.
  
  
  CONCLUSIONS
  Using a noninvasive, continuous technique to estimate cardiac sympathovagal balance, no significant variation in autonomic balance induced by spinal anesthesia was observed. However, untoward episodes of bradycardia and hypotension occurred in three patients, who could not be prospectively identified by the parameters studied.
authors.affiliation: Department of Anesthesia, Hôpital E. Herriot, and Laboratory of Physiology, School of Medicine, Lyon, France.
authors.forename: P
authors.initials: P
authors.lastname: Gratadour
authors.forename: J P
authors.initials: JP
authors.lastname: Viale
authors.forename: J
authors.initials: J
authors.lastname: Parlow
authors.forename: P
authors.initials: P
authors.lastname: Sagnard
authors.forename: H
authors.initials: H
authors.lastname: Counioux
authors.forename: G
authors.initials: G
authors.lastname: Bagou
authors.forename: G
authors.initials: G
authors.lastname: Annat
authors.forename: R
authors.initials: R
authors.lastname: Hughson
authors.forename: L
authors.initials: L
authors.lastname: Quintin
mesh_terms: D000759:Adjuvants, Anesthesia / Q000627:therapeutic use; D000328:Adult; D000775:Anesthesia, Spinal / Q000009:adverse effects; D000779:Anesthetics, Local; D017704:Baroreflex; D002045:Bupivacaine; D004562:Electrocardiography; D005039:Etilefrine / Q000494:pharmacology; D006439:Hemodynamics; D006801:Humans; D007552:Isotonic Solutions / Q000494:pharmacology; D008297:Male; D008874:Midazolam / Q000627:therapeutic use; D008875:Middle Aged; D011292:Premedication; D000077325:Ringer's Lactate; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000759:Adjuvants, Anesthesia; D000779:Anesthetics, Local; D007552:Isotonic Solutions; D000077325:Ringer's Lactate; D014662:Vasoconstrictor Agents; D008874:Midazolam; D002045:Bupivacaine; D005039:Etilefrine