title: Nitrous oxide attenuates pressor but augments norepinephrine response to laryngoscopy and endotracheal intubation.
abstract: Nitrous oxide (N(2)O) exerts a sympathomimetic action. We investigated whether N(2)O modifies the cardiovascular responses to tracheal intubation during general anesthesia. One-hundred healthy patients were assigned randomly to receive one of four concentrations (0%, 25%, 50%, or 75%; n = 25 each) of N(2)O in oxygen throughout the study beginning 3 min before tracheal intubation. Anesthesia was induced with IV thiopental (5-7 mg/kg) whereas patients were ventilated with designated concentrations of N(2)O. Tracheal intubation was facilitated with IV vecuronium (0.12 mg/kg). After intubation, all received 2% sevoflurane in oxygen via a semiclosed anesthesia circuit. Systolic arterial blood pressure, heart rate and rhythm, and plasma catecholamine concentrations were measured. The intubation significantly increased arterial blood pressure and heart rate. The maximum pressure changes were 46 +/- 21 and 65 +/- 24 mm Hg in 75% N(2)O and control groups, respectively (P < 0.05), being attenuated by N(2)O without affecting the tachycardiac response. Norepinephrine concentrations were increased at 1 min after the intubation, the magnitude of which was augmented by N(2)O. N(2)O did not affect the incidence of arrhythmias. It was shown that N(2)O suppressed the pressor response to endotracheal intubation, despite the augmented increase of norepinephrine concentrations.
  
  
  CONCLUSIONS
  We examined whether nitrous oxide modifies the cardiovascular response to endotracheal intubation because it activates the sympathetic nervous system. Nitrous oxide attenuated the pressor response, whereas it augmented the norepinephrine response to laryngoscopy and endotracheal intubation.
authors.affiliation: *Department of Anesthesiology and the †Research Institute of Medical Sciences, Chonnam National University Medical School, Gwangju, South Korea.
authors.forename: Kyung Y
authors.initials: KY
authors.lastname: Yoo
authors.forename: Sung T
authors.initials: ST
authors.lastname: Jeong
authors.forename: In H
authors.initials: IH
authors.lastname: Ha
authors.forename: JongUn
authors.initials: J
authors.lastname: Lee
mesh_terms: D000328:Adult; D018685:Anesthetics, Inhalation / Q000009:adverse effects*; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000453:epidemiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D001919:Bradycardia / Q000139:chemically induced / Q000453:epidemiology; D002395:Catecholamines / Q000097:blood; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D006973:Hypertension / Q000139:chemically induced / Q000453:epidemiology; D007022:Hypotension / Q000139:chemically induced / Q000453:epidemiology; D007442:Intubation, Intratracheal / Q000009:adverse effects*; D007828:Laryngoscopy / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000009:adverse effects*; D009638:Norepinephrine / Q000097:blood*; D013610:Tachycardia / Q000139:chemically induced / Q000453:epidemiology
chemical_list: D018685:Anesthetics, Inhalation; D002395:Catecholamines; D006454:Hemoglobins; D009609:Nitrous Oxide; D009638:Norepinephrine