title: Time-Dependent Decline in Multifocal Electroretinogram Requires Faster Recording Procedures in Anesthetized Pigs.
abstract: OBJECTIVE
  The time-dependent effect of anesthetics on the retinal function is debated. We hypothesize that in anesthetized animals there is a time-dependent decline that requires optimized multifocal electroretinogram (mfERG) recording procedures.
  
  
  METHODS
  Conventional and four-frame global-flash mfERG recordings were obtained approximately 15, 60, and 150 minutes after the induction of propofol anesthesia (20 pigs) and isoflurane anesthesia (nine pigs). In six of the propofol-anesthetized pigs, the mfERG recordings were split in 3-minute segments. Two to 4 weeks after initial recordings, an intraocular injection of tetrodotoxin (TTX) was given and the mfERG was rerecorded as described above. Data were analyzed using mixed models in SAS statistical software.
  
  
  RESULTS
  Propofol significantly decreases the conventional and global-flash amplitudes over time. The only significant effect of isoflurane is a decrease in the global-flash amplitudes. At 15 minutes after TTX injection several of the mfERG amplitudes are significantly decreased. There is a linear correlation between the conventional P1 and the global-flash DR mfERG-amplitude (R2= 0.82, slope = 0.72,P< 0.0001). There is no significant difference between the 3-minute and the prolonged mfERG recordings for conventional amplitudes and the global-flash direct response. The global flash-induced component significantly decreases with prolonged mfERG recordings.
  
  
  CONCLUSIONS
  A 3-minute mfERG recording and a single stimulation protocol is sufficient in anesthetized pigs. Recordings should be obtained immediately after the induction of anesthesia. The effect of TTX is significant 15 minutes after injection, but is contaminated by the effect of anesthesia 90 minutes after injection. Therefore, the quality of mfERG recordings can be further improved by determining the necessary time-of-delay from intraocular injection of a drug to full effect.
  
  
  CONCLUSIONS
  General anesthesia is a possible source of error in mfERG recordings. Therefore, it is important to investigate the translational relevance of the results to mfERG recordings in children in general anesthesia.
authors.affiliation: Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Nina Buus
authors.initials: NB
authors.lastname: Sørensen
authors.affiliation: Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Anders Tolstrup
authors.initials: AT
authors.lastname: Christiansen
authors.affiliation: Department of Neurology, Zealand University Hospital, Roskilde, Denmark.
authors.forename: Troels Wesenberg
authors.initials: TW
authors.lastname: Kjær
authors.affiliation: Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Kristian
authors.initials: K
authors.lastname: Klemp
authors.affiliation: Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: la Cour
authors.affiliation: Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Jens Folke
authors.initials: JF
authors.lastname: Kiilgaard
keywords: Porcine; experimental animal model; ketamine; neuromuscular blocker