title: Does anesthetic regimen influence implicit memory during general anesthesia?
abstract: BACKGROUND
  Implicit learning of intraoperative auditory stimuli during general anesthesia is very difficult to quantify but may require the presence of noxious stimulation. We hypothesized that an anesthetic regimen with a low dose of opioid would enhance implicit memory, while a regimen with a high dose of opioid would not.
  
  
  METHODS
  One hundred-twenty patients were randomized into 3 groups. All patients were anesthetized with a target-controlled infusion of propofol and remifentanil, targeting a Bispectral Index (BIS) value of 50. The remifentanil effect-site concentration (in ng/mL) was always double that of propofol (in μg/mL) in the first group and half of that in the second group. Patients in these 2 groups were played a list of 20 words via headphones during surgery. The third group served as control for memory tests and was not played any word during anesthesia. BIS was recorded during word presentation.
  
  
  RESULTS
  No statistical difference was found among the 3 groups regarding 3 different memory tests although 67.5% [50.7%; 80.9%] of the patients of the high-opioid group and 72.5% [55.9%; 84.9%] of the low-opioid group had at least 1 episode of BIS >60.
  
  
  CONCLUSIONS
  We could not demonstrate the presence of implicit or explicit memorization under propofol-remifentanil anesthesia either with a low- or a high-dose opioid anesthetic regimen.
authors.affiliation: From the Department of Anesthesiology, CHU-Tivoli, La Louviere, Belgium.
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Lequeux
authors.forename: Fidelie
authors.initials: F
authors.lastname: Hecquet
authors.forename: Philippe
authors.initials: P
authors.lastname: Bredas
mesh_terms: D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General / Q000523:psychology*; D018686:Anesthetics, Intravenous; D056805:Consciousness Monitors; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects*; D011939:Mental Recall / Q000187:drug effects; D008875:Middle Aged; D010880:Piperidines; D015742:Propofol; D011597:Psychomotor Performance / Q000187:drug effects; D021641:Recognition, Psychology / Q000187:drug effects; D000077208:Remifentanil; D013315:Stress, Psychological / Q000523:psychology; D055815:Young Adult
chemical_list: D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol