Otoprotective Effect of Cortexin, Cogitum, and Elkar Administered Simultaneously with Netromycin in the Experiment.

We studied possible otoprotective effect of drugs widely used for the correction of perinatal hypoxic brain damage in premature infants. The experiments were carried out on immature rabbits with an immature hearing organ. The auditory function was assessed by DPOAE and ABR methods in intact animals and rabbits treated with therapeutic doses of netromycin alone or in combination with the drugs that normalize metabolic processes in the brain (Cortexin, Cogitum, Elkar, vitamin B2, ATP, and cocarboxylase). It was found that the administered drugs produced an otoprotective effect and reduced the severity, but did not eliminate the ototoxic effect.

Effects of Cocarboxylase in Amikacin-Induced Ototoxicity in Immature Animals.

Possible otoprotective properties of cocarboxylase were studied on the model of amikacin-induced ototoxicity in immature rabbits. Auditory function was evaluated by the short-latency auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) tests. Administration of cocarboxylase after modeling of amikacin-induced ototoxicity resulted in a decrease in the ABR peak I threshold and prevented damage to the outer hair cells.

[The hearing function in the premature children following their treatment with the use of ototoxic antibiotics]. / Slukhovaia funktsiia nedonoshennykh detei posle lecheniia ototoksicheskimi antibiotikami.

The objective of the present study was the evaluation of the state of the auditory function in the premature children during the first year of life who underwent the neonatal treatment with various ototoxic antibiotics. A total of 232 newborn infants were available for the examination by the methods designed for recording distortion product optoacoustic emission (DPOAE) and short-latency auditory evoked potentials (SAEPs). The 'Statgraphics Centurion XV' program was used for the statistical treatment of the data obtained in the study. The results of recording DPOAE and SAEPs in 232 prematurely born children of different gestational age were used to evaluate their auditory function under conditions of treatment with various ototoxic antibiotics during the early neonatal period. It was shown that such treatment is likely to have an impact on the hearing function of premature children throughout the entire first year of life. Such influence can manifest itself as the enhanced threshold of the appearance of SAEPs peak V and the selective distortion of evoked responses recorded with the help of the DPOAE technique at a frequency of 4.6 kHz. It is concluded that all prematurely born children should be under observation of an otorhinolaryngologist-surdologist throughout the entire first year of life and, if appropriate, undergo the rehabilitative treatment at the earliest possible time. Moreover, the children with this condition must remain under the thorough follow-up care during at least 3 years including the yearly audiological evaluation and the comparative analysis of the results of previous observations for the timely identification of possible disturbances in the hearing function.

[The relationship between the parameters of evoked otoacoustical emission and tympanometry in the children born with the extremely low body weight]. / Vzaimosviaz' parametrov vyzvannoi otoakusticheskoi émissii i timpanometrii u detei, rozhdennykh s ékstremal'no nizkoi massoi tela.

The objective of the present study was to elucidate correlation between the parameters of evoked otoacoustical emission at the distorsion product otoacoustic emissionen frequency (DPOAE) and the results of tympoanometry performed at the probe tone frequencies of 226 Hz and 1 kHz in the children born with the extremely low body weight. The results of the study give evidence of the moderate correlation dependence between the strength of the cochlear acoustic response at DPOAE and the cohlear response amplitude at the frequencies of 2 kHz and 6 kHz from TTP (r=0.3; p=0.000) obtained at the tympanometry probe tone frequency of 1 kHz. The correlation between the magnitude of the acoustic response of the cochlea, the amplitude of this response at the frequencies of 2 kHz and 6 kHz, the width of the tympanograms, and their static compliance obtained in the studies at the tympanometry probe tone frequency of 1,000 Hz (r=0.3-0.5; p=0.001) was documented in the infants at the age of 6 months and 1 year.

Effect of Successive Administration of Vancomycin and Amikacin on Auditory Function of Immature Animals.

Effect of successive administration vancomycin and amikacin in therapeutic doses on immature auditory organ was compared to single administration of the same drugs in chronic experiments on immature rabbits by recording of short-latency auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE). Drug administration always increased significantly the ABR peak I threshold. Ototoxic antibiotics did not change DPOAE, but selectively affected activity of outer hair cells. No enhancement of the ototoxic effects was observed after successive administration of the two antibiotics.

[The results of primary audiological examination of the children presenting with intrauterine growth retardation and normotrophics born after multifetal and singleton pregnancies].

The objective of the present work was the comparative study of the state of the acoustic analayzer in the full-term and premature infants born after multifetal (MP) or singleton (SP) pregnancies with the body weight at birth corresponding to the gestational age (normotrophics) and presenting with intrauterine growth retardation (IUGR). The method of distortion product otoacoustic emissions (DPOAEs) was employed in the study. It has demonstrated that the normotrophic babies born at the gestational age over 34 weeks after singleton pregnancy pass the DPOAEstest significantly more frequently than normotrophics of the same gestational age born after multifetal pregnancy. Moreover, the unilateral impairment of hearing in the full-term infants born after multifetal pregnancy occurs more frequently than in those born after singleton pregnancy.

Auditory Function in Immature Animals after Two Consecutive Courses of Ototoxic Antibiotics.

In chronic experiments on immature rabbits receiving therapeutic courses of vancomycin, gentamicin, and consecutive administration of vancomicin and gentamicin by the scheme used in neonatology, hearing function was evaluated by the methods of auditory evoked potentials (auditory brainstem response, ABR) and distortion product otoacoustic emission (DPOAE). Comparison with the control group revealed ototoxic effects of all studied antibiotics that manifested in increased sound tolerance and more rapid shortening of latencies in 30-100 dB range. Higher thresholds were found only after gentamicin administration. Vancomycin administration significantly reduced the responses at 4 kHz. Subsequent gentamicin course did not potentiate this effect.

[Tympanometry in premature babies during the first year of life].

The objective of the present work was to study the tympanograms of the premature infants during the first year of their life and to determine the optimal time for performing high-frequency and low-frequency tympanometry in the babies of different gestational age. It was shown that the middle ear as an apparatus of the sound-transmitting system becomes to function stably by the 6th month of life although the mechanisms for regulation of stabilization develop only in the end of the first year. For this reason, tympanometry in the children of the gestational age 29 - 32 , 33 - 37 и 38 - 40 weeks should be performed using two frequencies of the probing tone (226 Hz and 1 kHz) up to the 6 months of life inclusive and from 28 weeks to 1 year.Key words: premature baby, tympanometry, acoustic function.

[The evaluation of the hearing function in the premature infants with intrauterine growth retardation during the third and sixth months of life by recording auditory steady-state response].

The objective of the present work was to study the function of the retrocochlear auditory pathway in the premature infants with intrauterine growth retardation (IGR) in comparison to that of the normotrophics of a similar gestational age during the third and sixth months of life by recording auditory steady-state responses (ASSR). The audiological examination by the method of auditory steady-state response (ASSR) involved 127 children at the 3d month of life and in 97 children at the 6th month of life. It was shown that the ASSR thresholds at certain frequencies during the 3d and 6th months of life of the children born after the 32d week of pregnancy were significantly higher than in the children born after 32 weeks gestation. The comparison of the two objective audiological methods, viz. distortion-product otoacoustic emission (DPOAE) and ASSR, indicates that both should be used to evaluate the hearing function during the third and sixth months of life to compensate for the discrepancy between the results obtained by either technique.

Effect of gentamicin on the auditory analyzer in sexually immature animals.

Auditory function of immature rabbits was evaluated using two electrophysiological methods, brainstem auditory evoked response (BAER) and distortion product otoacoustic emission (DPOAE), in chronic experiments following administration of therapeutic doses of gentamicin. Impairment of auditory function manifested in increased thresholds and decreased amplitude of the 1st BAER peak was established. DPOAE parameters were not significantly changed. It was suggested that gentamicin decreased activity of spiral ganglion neurocytes in animals with immature auditory analyzer.

Effects of amikacin on maturation of the auditory analyzer in rabbits.

We studied the dynamics of maturation of the hearing function by records of short-term latent brainstem evoked potentials and the effect of amikacin on maturation of the hearing function. The peripheral compartment of the auditory analyzer matures sooner than the central structures. Amikacin in therapeutic doses exhibited an ototoxic effect on the peripheral compartment of the auditory analyzer without impairing its central structures.