The effect of pentobarbital sodium and propofol anesthesia on multifocal electroretinograms in rhesus macaques

Abstract

We compared the suitability of pentobarbital sodium (PB) and propofol (PF) anesthetics for multifocal electroretinograms (mfERGs) in rhesus macaques. mfERGs were collected from 4 ocularly normal rhesus macaques. All animals were pre-anesthetized with intramuscular ketamine (10-15 mg/kg). Intravenous PB induction/maintenance levels were 15 mg/kg/2-10 mg/kg, and for PF, 2-5 mg/kg/6-24 mg/kg/h. There were 3 testing sessions with PB anesthesia and 5-7 testing sessions with PF anesthesia. All PB sessions were carried out before PF. First-order (K1) and second-order (first slice) kernels (K2.1) response density amplitude (RDA), implicit time (IT), and root mean square signal-to-noise ratios (RMS SNR) of the low-frequency (LFC) and high-frequency (HFC) components were evaluated. The use of PF or PB anesthesia resulted in robust, replicable mfERGs in rhesus macaques; however, RMS SNR of K1 LFC in ring and quadrant analyses was significantly larger for PF than for PB. Additionally, K1 RDA under PF was significantly larger than under PB for N1, P1 and P2 components (ring and quadrant), and for N2 (quadrant). PF IT was significantly prolonged (<1 ms) relative to PB IT for N1, P1 (ring) and N1 (quadrant) while PB IT was significantly prolonged (0.8-4.2 ms) relative to PF IT for N2 and P2 (ring and quadrant). K1 HFC and K2.1 LFC did not differ significantly between PB and PF in the ring or quadrant analyses. The response differences found with PB and PF anesthesia likely arise from variable relative effects of the anesthetics on retinal γ-aminobutyric acid (GABAA) receptors, and in part, on glycine and on glutamate receptors. Given the advantages of a stable anesthetic plane with continuous intravenous infusion and a smoother, more rapid recovery, PF is an appealing alternative for mfERG testing in rhesus macaques.

Regional Choroidal Blood Flow and Multifocal Electroretinography in Experimental Glaucoma in Rhesus Macaques

“…For example, in the animal with only a 10% percent axonal loss, it is possible that the remaining 90% of axons, although visible histologically, were non-or partially functional. To test this hypothesis, we analyzed the central hexagon of the seven-element mfVEP 42 that was recorded at the same time as the mfERG. Since we were comparing this with postmortem anatomy, we looked at the final mfVEP obtained prior to euthanasia.…”

“…The mfERG testing procedure was performed as previously described. 42 Briefly, the animals were preanesthetized with ketamine hydrochloride (15 mg/kg, intramuscular). Propofol was used to induce each animal into a deeper level of anesthesia.…”

Time-Dependent Decline in Multifocal Electroretinogram Requires Faster Recording Procedures in Anesthetized Pigs

“…Several studies have shown that electroretinogram amplitudes are affected by anesthesia. 1 – 6 However, since mfERG is one of the best methods to examine retinal function in vivo we find it relevant to explore and minimize the effect of anesthetic agents. Theoretically, it is possible to reduce the effect of anesthesia on mfERG by altering the concentration, agent, or duration.…”

“… 9 In experimental studies recordings typically last from 3 to 14 minutes. 2 , 3 , 6 , 10 – 18 The balance between the signal-to-noise ratio and the exhaustion of the examined individual determines the necessary duration of a recording. It is likely that when animals are anesthetized the noise is minimal and shorter recordings would be sufficient.…”

“…In porcine mfERG studies, propofol has been considered the drug of choice since it alters the baseline mfERG the least. 2 – 4 Propofol anesthesia also is preferred in the clinic when mfERG recordings are obtained in patients unable to cooperate. However, the possible existence of a time-dependent effect of propofol on the mfERG could be a problem.…”