Abstract
Abstract: :
Purpose: To investigate the effects of different anesthesia regimens on electroretinographic evaluations. Methods: Ganzfeld-ERGs obtained from conscious (n=9), sedated (chloral hydrate or pentobarbital sodium, n=9) and anesthetized (halothane or isoflurane in combination with N20, n=9; propofol n=2) young patients aged 2 to 9 were studied. Protocols were similar in all conditions and consisted in rod-isolated and bright-flash responses in scotopic conditions and cone-isolated responses under photopic conditions. Animal studies were performed in pigs maintained under isoflurane(n=9), ketamine (n=11) and propofol (n=2). Ganzfeld-, Pattern and Multifocal ERGs were obtained in control conditions and after at least 2 weeks post optic nerve section to eliminate the retinal ganglion cells. Results: Sedation produced minimal ERG changes in our clinical population, with a decrease of less than 20% in scotopic activity with no implicit time prolongation and no change in photopic activity. Anesthesia reduced the amplitude of the scotopic recordings by 25% and prolonged the implicit time of all parameters measured by 2-3 ms. The photopic OFF response (OP4 and 5) was predominantly altered, with attenuation reaching 75% and delays up to 15 ms. In the pig optic nerve section model, responses from the experimental eye were indistinguishable from the control one when recordings were performed under isoflurane anesthesia, suggesting that responses generated by retinal ganglion cells were abolished; these responses were present when the same animals were maintained under ketamine or propofol. Conclusions: In a clinical environment, it is imperative that appropriate normative data be used to assess ERGs obtained under sedation and anesthesia. Retinal ganglion cell components and the OFF responses likely originating from ionotropic glutamatergic receptors on bipolar cell appear particularly vulnerable to halogenated anesthetic agent such as isoflurane.
Keywords: electroretinography: clinical • retina • drug toxicity/drug effects