title: Effects of remifentanil/propofol in comparison with isoflurane on dynamic cerebrovascular autoregulation in humans.
abstract: BACKGROUND
  This study investigates the effects of remifentanil and propofol in comparison to isoflurane on dynamic cerebrovascular autoregulation in humans.
  
  
  METHODS
  In 16 awake patients dynamic cerebrovascular autoregulation was measured using transcranial Doppler sonography (TCD). Thereafter patients were intubated, ventilated with O2/air (FiO2=0.33) and randomly assigned to one of the following anesthetic protocols: group 1 (n=8): 0.5 microg x kg(-1) x min(-1) remifentanil combined with a propofol-target plasma concentration of 1.5 microg x ml(-1) group 2 (n=8): 1.8 % isoflurane (1.5 MAC). Following 20 min of equilibration the autoregulatory challenge was repeated. Arterial blood gases and body temperature were maintained constant over time.
  
  
  METHODS
  Mann-Whitney U-test and Wilcoxon signed-rank test.
  
  
  RESULTS
  Dynamic autoregulation was intact in all patients prior to induction of anesthesia expressed by an autoregulatory index (ARI) of 5.4+/-1.21 (mean+/-SD, group 1) and 5.9+/-0.98 (mean+/-SD, group 2). With remifentanil/propofol anesthesia dynamic autoregulation was similar to the awake state (group 1: ARI=4.9+/-0.88). In contrast, autoregulatory response was delayed with 1.5 MAC isoflurane (group 2, ARI=2.1+/-0.92) (P<0.05).
  
  
  CONCLUSIONS
  These data show that dynamic cerebrovascular autoregulation is maintained with remifentanil-based total intravenous anesthesia. This is consistent with the view that narcotics (and hypnotics) do not alter the physiologic cerebrovascular responses to changes in MAP. In contrast, 1.5 MAC isoflurane delays cerebrovascular autoregulation compared to the awake state.
authors.affiliation: Klinik für Anaesthesiologie der Technischen Universität München, Klinikum rechts der Isar, Munich, Germany. k.engelhard@lrz.tu-muenchen.de
authors.forename: K
authors.initials: K
authors.lastname: Engelhard
authors.forename: C
authors.initials: C
authors.lastname: Werner
authors.forename: O
authors.initials: O
authors.lastname: Möllenberg
authors.forename: E
authors.initials: E
authors.lastname: Kochs
mesh_terms: D000328:Adult; D000368:Aged; D019162:Anesthetics, Combined / Q000008:administration & dosage*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D010880:Piperidines / Q000008:administration & dosage*; D015742:Propofol / Q000008:administration & dosage*; D000077208:Remifentanil; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D010880:Piperidines; D007530:Isoflurane; D000077208:Remifentanil; D015742:Propofol