title: Effects of intravenous anesthetic agents on middle cerebral artery blood flow velocity during induction of general anesthesia.
abstract: OBJECTIVE
  Our objective was to quantify the effects of intravenous anesthetics on values measured by or derived from transcranial Doppler sonography (TCD) during induction of general anesthesia.
  
  
  METHODS
  We recorded blood flow velocity in the middle cerebral artery (V-MCA) before, during, and after induction of general anesthesia in six groups of young patients without intracranial pathology (n = 10 each) using TCD. Patients were randomized to receive either 2 mg/kg propofol, 1.5 mg/kg methohexital, 5 mg/kg thiopental, 0.3 mg/kg etomidate, 2 micrograms/kg fentanyl and 0.15 mg/kg midazolam, or 1.5 mg/kg ketamine and 0.15 mg/kg midazolam intravenously. At 2 min after injection, each patient was intubated and given isoflurane 0.8% and nitrous oxide 66% in oxygen. Ventilation was set to achieve an end-tidal PCO2 of 40 mm Hg. V-MCA, arterial blood pressure, heart rate, hematocrit, and PCO2 (venous samples) were measured before and 1, 3, 5, 10, and 30 min after induction of anesthesia.
  
  
  RESULTS
  The preinduction data were not different between groups. At 1 min after injection, propofol, thiopental, methohexital, and etomidate significantly decreased V-MCA. TCD values were only slightly affected following fentanyl/midazolam. Ketamine/midazolam induced a modest rise in V-MCA. After endotracheal intubation, V-MCA increased in all groups, and slowly declined thereafter.
  
  
  CONCLUSIONS
  Under the circumstances of our study, values derived from TCD measurements responded differently to the agents used to induce general anesthesia in nonneurosurgical patients.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Justus-Liebig-University, Giessen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Thiel
authors.forename: B
authors.initials: B
authors.lastname: Zickmann
authors.forename: H
authors.initials: H
authors.lastname: Roth
authors.forename: G
authors.initials: G
authors.lastname: Hempelmann
mesh_terms: D000328:Adult; D000768:Anesthesia, General; D000771:Anesthesia, Intravenous; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D001783:Blood Flow Velocity / Q000187:drug effects; D002536:Cerebral Arteries / Q000000981:diagnostic imaging* / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D006801:Humans; D007530:Isoflurane; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D018686:Anesthetics, Intravenous; D007530:Isoflurane