title: [Reduction of the concentration of isoflurane prevents tachycardia and hypertension associated with tracheal intubation].
abstract: BACKGROUND
  High concentration of isoflurane often induces not only tachycardia but also hypertension during induction of anesthesia and causes further hyperdynamic changes after tracheal intubation.
  
  
  METHODS
  Forty patients, ASA physical status I, were randomly assigned to receive 4% or 2.5% isoflurane. Anesthesia was induced with thiamylal and vecuronium followed by mask ventilation with 0.5% isoflurane in oxygen. Isoflurane concentration was gradually increased to 4% or 2.5% in 2 min and the trachea was intubated after 3 min. Systolic blood pressure (SBP) and heart rate (HR) were recorded every minute from induction of anesthesia.
  
  
  RESULTS
  Mask ventilation with isoflurane induced a significant increase in HR in both groups, but the HR just before intubation was significantly lower in the 2.5% group than in the 4% group. SBP was significantly decreased in the 2.5% group, but a transient increase was seen in the 4% group. Tracheal intubation induced a marked increase in HR in both groups, but the HR was significantly lower in the 2.5% group than in the 4% group (115 +/- 14 and 130 +/- 18 beats x min(-1), respectively; P < 0.01). SBPs just after intubation were 166 +/- 24 and 154 +/- 20 mmHg in the 4% and 2.5% groups, respectively. The difference between the groups was not significant, but the patients in whom the SBP increased more than 180 mmHg were significantly fewer in the 2.5% group than in the 4% group (P < 0.05).
  
  
  CONCLUSIONS
  Reduction of the isoflurane concentration from 4% to 2.5% during induction of anesthesia made the circulation stable, and decreased the incidence of excessive tachycardia and hypertension after tracheal intubation.
authors.affiliation: Department of Anesthesia, Hakodate Municipal Hospital, Hakodate 041-8680.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Masayasu
authors.initials: M
authors.lastname: Nakayama
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Namiki
mesh_terms: D000328:Adult; D000769:Anesthesia, Inhalation; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000517:prevention & control*; D007442:Intubation, Intratracheal; D007530:Isoflurane / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D013610:Tachycardia / Q000517:prevention & control*; D013840:Thiamylal; D014673:Vecuronium Bromide
chemical_list: D013840:Thiamylal; D014673:Vecuronium Bromide; D007530:Isoflurane