The effect of nitrous oxide on hearing

The effect of nitrous oxide and isoflurane on the total RNA yield from the cochlea of the rats

The possible mechanism of inhalation anesthetics on the internal auditory impairment of the rat was investigated by determining the effect of nitrous oxide (N(2)O) and isoflurane on the total RNA yield from the cochlea of the rats. Thirty healthy Wistar rats were randomly divided into 3 groups: group C (control group, n=10) with a 3-h unremitting inhalation of 50% O(2), group N (experiment group, n=10) with a continuous inhalation of 50% N(2)O+50% O(2) for 3 h, and group I (experiment group, n=10) with a 3-h sustained inhalation of 2.5% isoflurane. The TRIzol in combination with RNeasy was used to respectively extract the total RNA from cochlea of rats in the 3 groups. Spectrophotometry was used to detect total RNA yield and electrophoresis to detect the quality. The total RNA extracted from the cochlea of the rats in the groups C and N was 7.69 and 6.51 microg, respectively. There was a 15% decrease in the N group as compared with group C. The total RNA from the rats in the group I was 7.32 microg, and there was hardly any change in the group as compared with the group C. The value of A(260)/A(280) in groups C, N and I was 2.07, 2.04 and 2.04, respectively, showing a very high RNA purity. The result of gel electrophoresis suggested that there was no degradation in the total RNA. It was suggested that the interference of N(2)O on the cochlear RNA yield might be one of the reasons which cause an injury of the ear. The isoflurane shows no harm on the hearing.

Middle Ear Pressure Changes During Anesthesia With or Without Nitrous Oxide are Similar Among Airway Devices

We tested the hypothesis that middle ear pressure (MEP) is influenced by the choice of airway device during anesthesia with or without nitrous oxide (N2O) in the gas mixture. Eighty consecutive anesthetized, paralyzed ventilated patients (ASA physical status I-II, 18-65 yr) were randomly allocated for airway management with the orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, or laryngeal tube suction with or without N2O 66% in the gas mixture. MEP was measured from both ears in random order by a blinded observer before induction of anesthesia and every 10 min for 70 min. In the N2O groups, N2O was changed to air after 40 min. There were no differences in MEP among the airway devices in the N2O or air groups. MEP was unchanged in the air groups but increased in the N2O groups with N2O (P < 0.0001) and decreased with air (P < 0.02). Baseline values for MEP were similar, but MEP was always higher for the N2O groups (P < 0.001). We conclude that the choice of airway device does not influence MEP among orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, and laryngeal tube suction during anesthesia with or without N2O in the gas mixture.

Effects of 900 MHz electromagnetic fields exposure on cochlear cells' functionality in rats: Evaluation of distortion product otoacoustic emissions

In recent years, the widespread use of mobile phones has been accompanied by public debate about possible adverse consequences on human health. The auditory system is a major target of exposure to electromagnetic fields (EMF) emitted by cellular telephones; the aim of this study was the evaluation of possible effects of cellular phone-like emissions on the functionality of rat's cochlea. Distortion Products OtoAcoustic Emission (DPOAE) amplitude was selected as cochlea's outer hair cells (OHC) status indicator. A number of protocols, including different frequencies (the lower ones in rat's cochlea sensitivity spectrum), intensities and periods of exposure, were used; tests were carried out before, during and after the period of treatment. No significant variation due to exposure to microwaves has been evidenced.