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Nina Buus Buus Sørensen, Anders Tolstrup Christiansen, Troels Wesenberg Kjær, Kristian Klemp, Morten D De La Cour, Jens F Kiilgaard; Increasing quality of the multifocal electroretinogram by reducing duration of anesthesia. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5760.
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The time-dependent effect of anesthetics on the multifocal electroretinogram (mfERG) is debated. We tested the hypothesis that reduced duration of anesthesia and stimulation improves the quality of the mfERG amplitudes in the anesthetized animal.
Conventional and global flash mfERG recordings were obtained 15 minutes, one hour and two hours after the induction of Propfol anesthesia (20 pigs) and Isofluran anesthesia (9 pigs). In 6 of the Propofol-anesthetized pigs, the mfERG was recorded as 3 minute segments. The recorded MfERG were first influenced by the anesthetic alone and one week later by both the anesthetic and an intraocular injection of Tetrodotoxin (TTX). Outcome was the major mfERG amplitudes. Data was analyzed using mixed models in SAS statistical software.
Propofol significantly decreases conventional mfERG amplitudes (N1: p=0.0004, P1: p<0.0001, N2: p<0.05) and global flash mfERG amplitudes (DR: p<0.0001, iN1: p<0.0001, iP2: p<0.0001). Isofluran induces a trend towards a decrease in conventional amplitudes and significantly decreases global flash amplitudes (DR: p=0.0005 and iP2: p=0.04). A significant effect of TTX is found as early as 15 minutes after intraocular injection on the conventional mfERG amplitudes in both anesthesia groups (Propofol-N2: p=0.02, Isofluran-P1: p=0.04 and Isofluran-N2: p=0.0009). TTX produced no significant effect on the amplitudes of the induced mfERG. There is a linear correlation between the P1 and DR amplitudes regarding size, implicit time and fluctuations. For the conventional mfERG there is no significant difference between the 3 minutes and the 7 minutes recordings. The global flash iP2 amplitude is significantly decreased after 10 (p=0.02) and 14 (p=0.002) minutes compared to the 3 minute recording. There is no significant difference between the 3 minute and the longer recordings for DR and iN1.
In Propofol and Isofluran anesthesia, there is a time-dependent decrease in both conventional and global flash mfERG amplitudes. Within 15 minutes after intraocular injection it is possible to measure the effect of TTX. Increased quality of the mfERG can be obtained by reducing time in anesthesia. Therefore, recordings should be initiated within 15 minutes after induction of anesthesia, duration of recordings should be limited to 3 minutes and for most purposes an induced mfERG recording is sufficient.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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