title: Lipopolysaccharide infusion enhances dynamic cerebral autoregulation without affecting cerebral oxygen vasoreactivity in healthy volunteers.
abstract: BACKGROUND
  Sepsis may be associated with disturbances in cerebral oxygen transport and cerebral haemodynamic function, thus rendering the brain particularly susceptible to hypoxia. The purpose of this study was to assess the impact of isocapnic hypoxia and hyperoxia on dynamic cerebral autoregulation in a human-experimental model of the systemic inflammatory response during the early stages of sepsis.
  
  
  METHODS
  A total of ten healthy volunteers were exposed to acute isocapnic inspiratory hyperoxia (FIO₂ = 40%) and hypoxia (FIO₂ = 12%) before and after a 4-hour lipopolysaccharide (LPS) infusion (2 ng kg-1). Middle cerebral artery blood follow velocity was assessed using transcranial Doppler ultrasound, and dynamic autoregulation was evaluated by transfer function analysis.
  
  
  RESULTS
  Transfer function analysis revealed an increase in the phase difference between mean arterial blood pressure and middle cerebral artery blood flow velocity in the low frequency range (0.07-0.20 Hz) after LPS (P<0.01). In contrast, there were no effects of either isocapnic hyperoxia or hypoxia on dynamic autoregulation, and the cerebral oxygen vasoreactivity to both hyperoxia and hypoxia was unaffected by LPS.
  
  
  CONCLUSIONS
  The observed increase in phase suggests that dynamic cerebral autoregulation is enhanced after LPS infusion and resistant to any effects of acute hypoxia; this may protect the brain from ischaemia and/or blood-brain barrier damage during the early stages of sepsis.
authors.forename: Ronan M G
authors.initials: RM
authors.lastname: Berg
authors.forename: Ronni R
authors.initials: RR
authors.lastname: Plovsing
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Evans
authors.forename: Claus B
authors.initials: CB
authors.lastname: Christiansen
authors.forename: Damian M
authors.initials: DM
authors.lastname: Bailey
authors.forename: Niels-Henrik
authors.initials: NH
authors.lastname: Holstein-Rathlou
authors.forename: Kirsten
authors.initials: K
authors.lastname: Møller
mesh_terms: D001783:Blood Flow Velocity; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000187:drug effects*; D064368:Healthy Volunteers; D006439:Hemodynamics; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D007262:Infusions, Intravenous; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging; D010100:Oxygen / Q000097:blood; D018805:Sepsis / Q000503:physiopathology; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
chemical_list: D008070:Lipopolysaccharides; D010100:Oxygen