title: Nitrous oxide-induced slow and delta oscillations.
abstract: OBJECTIVE
  Switching from maintenance of general anesthesia with an ether anesthetic to maintenance with high-dose (concentration >50% and total gas flow rate >4 liters per minute) nitrous oxide is a common practice used to facilitate emergence from general anesthesia. The transition from the ether anesthetic to nitrous oxide is associated with a switch in the putative mechanisms and sites of anesthetic action. We investigated whether there is an electroencephalogram (EEG) marker of this transition.
  
  
  METHODS
  We retrospectively studied the ether anesthetic to nitrous oxide transition in 19 patients with EEG monitoring receiving general anesthesia using the ether anesthetic sevoflurane combined with oxygen and air.
  
  
  RESULTS
  Following the transition to nitrous oxide, the alpha (8-12 Hz) oscillations associated with sevoflurane dissipated within 3-12 min (median 6 min) and were replaced by highly coherent large-amplitude slow-delta (0.1-4 Hz) oscillations that persisted for 2-12 min (median 3 min).
  
  
  CONCLUSIONS
  Administration of high-dose nitrous oxide is associated with transient, large amplitude slow-delta oscillations.
  
  
  CONCLUSIONS
  We postulate that these slow-delta oscillations may result from nitrous oxide-induced blockade of major excitatory inputs (NMDA glutamate projections) from the brainstem (parabrachial nucleus and medial pontine reticular formation) to the thalamus and cortex. This EEG signature of high-dose nitrous oxide may offer new insights into brain states during general anesthesia.
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Kara J
authors.initials: KJ
authors.lastname: Pavone
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Department of Anaesthesia, Harvard Medical School, Boston, MA, USA.
authors.forename: Oluwaseun
authors.initials: O
authors.lastname: Akeju
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Aaron L
authors.initials: AL
authors.lastname: Sampson
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Kelly
authors.initials: K
authors.lastname: Ling
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Department of Anaesthesia, Harvard Medical School, Boston, MA, USA.
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Purdon
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA; Department of Anaesthesia, Harvard Medical School, Boston, MA, USA; Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA, USA; Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA; Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA. Electronic address: enb@neurostat.mit.edu.
authors.forename: Emery N
authors.initials: EN
authors.lastname: Brown
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General / Q000639:trends; D000769:Anesthesia, Inhalation / Q000639:trends; D003700:Delta Rhythm / Q000187:drug effects* / Q000502:physiology; D004569:Electroencephalography / Q000187:drug effects* / Q000639:trends; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D009609:Nitrous Oxide
keywords: EEG; General anesthesia; NMDA-receptor blockade; Parabrachial nucleus; Slow waves