Effects of Isoflurane on the Auditory Brainstem Responses and Middle Latency Responses of Rats

Abstract

The present findings indicate that both ABR and MLR latencies are increased by isoflurane in a concentration-dependent manner, whilst the anesthetic-induced attenuation in amplitude does not appear to be related to the isoflurane concentration.

A comparison of the effects of isoflurane and ketamine anesthesia on auditory brainstem response (ABR) thresholds in rats

“…This is in agreement with previous work demonstrating the effects of isoflurane on ABR waveform, latency and amplitude (Heneghan et al, 1987;Smith and Mills, 1989;Santarelli et al, 2003). The present research expands those findings by comparing threshold levels across a broad range of stimuli, and by directly comparing isoflurane to ketamine/xylazine, another NMDA antagonist general anesthetic.…”

“…A decrease in hair cell damage has also been reported, suggesting that isoflurane may protect the auditory system at a cochlear level, as well as at the central level. Santarelli et al (2003) pointed out that glutamatergic inner hair cells may be sensitive to isoflurane antagonism. Attenuation of hair cell motility would contribute to ABR threshold elevation as well as cochlear protection.…”

“…Empirical data must be brought to bear on the question of how specific anesthetics affect the ABR. Santarelli et al (2003) reported increased latency and decreased amplitude of several ABR peaks after isoflurane administration. Ferber-Viart et al (1998) compared the effect of isoflurane and propofol on otoacoustic emissions, but hearing threshold consequences were not examined.…”

Effects of isoflurane on auditory evoked potentials in the cochlea and brainstem of guinea pigs

“…ABR amplitude was unaffected in these studies (Manninen et al, 1985;Sebel et al, 1986;Lloyd-Thomas et al, 1990). In rats isoflurane has been shown to increase the latency of all ABR peaks including peak I (Santarelli et al, 2003). Since the early peak I of the ABR is thought to represent auditory nerve activity (Legatt, 2002), this indirectly indicates that the auditory nerve response is delayed in rats, but not in humans.…”

“…With regard to the ABR, general anesthetics such as barbiturates (Shapiro et al, 1984;Drummond et al, 1985;Church and Shucard, 1987), ketamine (Church and Gritzke, 1987) and the halogenated volatiles (Dubois et al, 1982;Sainz et al, 1987;Santarelli et al, 2003) typically increase its latency, especially of later peaks, without affecting the amplitude. Nitrous oxide (Manninen et al, 1985), and the opioids morphine and fentanyl (Samra et al, 1984(Samra et al, , 1985 do not affect the ABR.…”