title: Transcranial Doppler sonography: nitrous oxide and cerebral blood flow velocity in children.
abstract: To determine the effect of nitrous oxide (N2O) on cerebral blood flow velocity (CBFV) and cerebrovascular resistance index (RI+) in children, ten ASA physical status I or II patients aged one to eight years old, scheduled for urological procedures, were studied. Anaesthesia was induced with thiopentone 2 mg.kg-1, fentanyl 5 micrograms.kg-1 and diazepam 0.3 mg.kg-1. Muscular relaxation was ensured by using vecuronium 0.1 mg.kg-1. After tracheal intubation, anaesthesia was randomly assigned to either a mixture of air in oxygen (N2/O2) or 70% N2O in oxygen (N2O/O2) producing an FIO2 of 30%. Three sets of measurements of CBFV and RI+ were made with both gas mixtures. The CBFV and RI+ were measured in the middle cerebral artery (MCA) with a transcranial Doppler monitor. Measurements were made while using the initial gas mixture, then the second gas mixture was administered, and finally, the patient again was given the initial gas mixture. A continuous caudal epidural or lumbar epidural block was performed before skin incision. Neuromuscular blockade was maintained with vecuronium 0.05 mg.kg-1. Temperature, heart rate, end-tidal CO2, arterial oxygen saturation, haematocrit and arterial blood pressure were maintained constant. Ventilation was adjusted to achieve normocapnia. The CBFV increased when 70% N2/O2 was replaced by 70% N2O/O2 (P less than 0.05) while the CBFV decreased when 70% N2/O2 was readministered (P less than 0.05). Likewise, the CBFV decreased when 70% N2O/O2 was replaced by 70% N2/O2 (P less than 0.05) while the CBFV increased when 70% N2O/O2 was readministered (P less than 0.05).
authors.affiliation: Department of Anaesthesia, Hospital for Sick Children, University of Toronto, Ontario, Canada.
authors.forename: J E
authors.initials: JE
authors.lastname: Leon
authors.forename: B
authors.initials: B
authors.lastname: Bissonnette
mesh_terms: D000769:Anesthesia, Inhalation; D001783:Blood Flow Velocity / Q000187:drug effects*; D001921:Brain / Q000098:blood supply*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D002648:Child; D002675:Child, Preschool; D004453:Echoencephalography / Q000379:methods; D006801:Humans; D007223:Infant; D009584:Nitrogen / Q000008:administration & dosage; D009609:Nitrous Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D010100:Oxygen / Q000008:administration & dosage; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects*
chemical_list: D009609:Nitrous Oxide; D009584:Nitrogen; D010100:Oxygen