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Biomedical subjects

L Lyttkens

Publications and source records attributed to L Lyttkens.

At least 37 records · Page 2Linked to original sources
PubMed1986

Treatment of tinnitus by external electrical stimulation.

Transcutaneous electrical stimulation was used in 5 consecutive patients suffering from troublesome tinnitus. The study included three parts. Part one constituted an open trial using the stimulation equipment. During this part, 2 patients reported a reduced subjective tinnitus loudness. These 2 patients proceeded to part two where the effect from the stimulation equipment was compared with the effect from a placebo apparatus in an experimental double-blind trial. One of these 2 patients reported similar effects from active stimulation and placebo, while the other patient reported a constant positive effect from the active stimulation and no effect at all from placebo. The latter patient continued to part three where the effect of the equipment was studied over a 3-month period. Throughout the study, continuous self-recordings of the complaints was used. The results show that the electrical stimulation had a genuine tinnitus-reducing effect in one patient, remaining over a 3-month period, a positive placebo effect in one patient, but no effect in 3 patients. To determine the applicability of this method in the clinical population, carefully designed outcome studies, with appropriate control conditions, are required.

Adult↗
PubMed1986

Pharmacological treatment of tinnitus with special reference to the role of melanin.

Local anaesthetics have hitherto been thought to exert their effects on tinnitus through a centrally operative mechanism, analogously to their effects in epilepsy and central pain. Evidences for a peripheral mechanism, probably related to the affinity of these drugs to inner ear melanin, are reviewed. The physico-chemical properties of melanin and findings indicating that this substance plays a role in hearing are also discussed.

Ear, Inner↗
PubMed1986

Ototoxicity of kanamycin in albino and pigmented guinea pigs. I. A morphologic and electrophysiologic study.

Ototoxic drugs of the aminoglycoside type have been shown to accumulate to melanin, suggesting a possible mechanism for their ototoxicity. The present study was undertaken by combining electrophysiologic and morphologic methods to investigate whether the ototoxicity of kanamycin is different in pigmented and albino guinea pigs. In pigmented animals a kanamycin dose of 200 mg per kilogram of body weight per day resulted in hearing loss together with loss of both inner and outer hair cells. The albino animals in the same dose group showed significantly less hearing loss and hair cell degeneration. With daily doses of 20 and 60 mg/kg/day, no difference in ototoxicity was found between the pigmented and albino animals. The results support the hypothesis that affinity of kanamycin to inner ear melanin might be responsible for the difference in ototoxicity between albino and pigmented guinea pigs.

Animals↗
PubMed1985

Psychological treatment of tinnitus. An experimental group study.

Twenty-four patients with moderately severe (grade 2) to severe (grade 3) subjective tinnitus participated in an experimental group study. The patients were randomly assigned to a treatment group and a waiting-list control group. Treatment was given with a coping technique and comprised 10 one-hour sessions. Following a corresponding period without treatment, the control group was treated similarly. Daily self-recording of the subjective tinnitus loudness, the discomfort from the tinnitus, depression and irritation was performed before and after treatment. In addition, psychoacoustic measurement was undertaken on three occasions. The treatment group improved significantly more than the waiting-list control group. After treatment of the latter group, combined data of both groups showed statistically significant improvements in all variables. The results show that tinnitus annoyance can be treated by psychological methods.

Adult↗
PubMed1985

The effects of TTS-scopolamine, dimenhydrinate, lidocaine, and tocainide on motion sickness, vertigo, and nystagmus.

The effects of TTS-scopolamine, dimenhydrinate, lidocaine, and tocainide on motion sickness and vertigo and on caloric and postrotatory nystagmus were evaluated in healthy volunteers. TTS-scopolamine was administered transdermally (delivering approximately 10 micrograms X h-1 scopolamine base) and 100 mg dimenhydrinate orally. Lidocaine and tocainide were administered intravenously (average plasma concentration of lidocaine 6 mol X L-1 and of tocainide 20 mol X L-1). TTS-scopolamine and dimenhydrinate significantly reduced vertigo induced by calorization of the ears, nausea provoked with Coriolis maneuvre, and nystagmus in caloric and rotatory tests. During treatment with lidocaine and tocainide no alleviation of vertigo and nausea was observed. Caloric nystagmus was reduced but rotation induced nystagmus was virtually unchanged. Presumably the motion sickness drugs act at the brain stem where TTS-scopolamine and dimenhydrinate have their target cells in the vestibular nuclei. Furthermore, the alleviation of motion sickness was linked to a decline of nystagmus. Lidocaine and tocainide, the action of which in vertigo and nausea in patients is proposed to be on the vestibular end organs and the supratentorial brain structures, consistently failed to alleviate motion sickness.

Administration, Topical↗
PubMed1984

Local anaesthetics and tinnitus. Proposed peripheral mechanism of action of lidocaine.

To elucidate the question whether lidocaine reduces tinnitus by a central or by a peripheral mechanism of action, its effect on tinnitus was compared with that of QX-572, a quaternary ammonium derivative of lidocaine which does not readily penetrate the blood-brain barrier. The results of experimental as well as clinical investigations indicate that the effects of lidocaine and QX-572 on tinnitus are mediated by a peripheral mechanism possibly related to their accumulation on inner ear melanin.

Animals↗
PubMed1984

Tocainide and tinnitus. Clinical effect and site of action.

Tocainide, an amine analogue of lidocaine, which can be taken orally, was tested on 9 patients with severe tinnitus. 6 patients responded to the drug. In 4 patients the effect ceased after about 2 weeks despite continuous medication. 2 patients are still on this medication after more than 2 years. The binding of tocainide to melanin was analysed in vitro and in vivo in rats. It was concluded that the effect of tocainide on tinnitus is mediated by a peripheral mechanism possibly related to the accumulation on inner ear melanin.

Animals↗
PubMed1984

Tinnitus--incidence and handicap.

A questionnaire investigation, comprising 1091 patients, was conducted at a hearing centre. A majority of patients, 59%, claimed that they were troubled by tinnitus. A strong correlation was found between the laterality of tinnitus and that of subjective hearing loss. Neither a greater degree of hearing loss nor a longer duration of tinnitus was shown to be associated with more severe tinnitus. Among patients with both subjective hearing loss and tinnitus, 23% stated that tinnitus was the greater problem and 38% that their tinnitus and hearing loss were equally troublesome. The corresponding figures for patients with hearing impairment of such a degree that a hearing aid had been fitted were 9% and 41% respectively. Stress symptoms such as headache, tension of facial muscles and sleep disturbances were correlated to tinnitus. Psychosomatic complaints should therefore be taken into account in the treatment of tinnitus. Of patients with tinnitus, 83% were interested in obtaining treatment for their tinnitus. It is postulated that the previously reported predominance of left-sided tinnitus is due to a higher frequency of left-sided hearing impairment. A majority of patients with tinnitus and hearing impairment regarded their tinnitus as the major problem. Efforts towards investigation and treatment of tinnitus might therefore considerably improve the prospects for hearing rehabilitation.

Hearing Aids↗
PubMed1982

Hearing defects of noise trauma type with lack of noise exposure.

Screening audiometry in children not infrequently reveals a 4 kHz dip. Evidence for noise trauma as the etiological background of this 4 kHz dip have been presented in the literature. Thirty children with hearing defects of this characteristic type and no history of noise exposure were studied. Their mean age was 14 years and the average observation time 4.2 years. Slight progression of hearing impairment (greater than 15 dB at two frequencies) was noted in 3 children (10%). A history of hearing defects in the family was found in 76%, as against 17% in a control group. Abnormal elevation of stapedius reflex thresholds was observed in 83% of the material. It is concluded that in children with a 4 kHz dip and no history of significant exposure to noise, genetic disposition is the predominant etiological element underlying the hearing defect. There was no indication of increased sensitivity to general noise exposure, but as always in sensorineural high frequency hearing loss avoidance of significant exposure to noise is to be recommended.

Adolescent↗
PubMed1979

New parachute cuff and positive end-expiratory pressure to minimize tracheal injury and prevent aspiration.

A new parachute cuff has been tested in combination with a positive end-expiratory pressure (PEEP) on mongrel dogs. During positive-pressure ventilation the intracuff and intratracheal pressures showed synchronous, identical pressure variations, and therefore theoretically with this type of cuff the pressure against the tracheal wall would be minimal. The cuff provided a seal against gas leakage from the lungs throughout the entire test period, i.e., for up to 7 h. To avoid aspiration of mouth contents during the passive exhalation phase, different amounts of PEEP were tested. A PEEP of 4.0--8.0 cm H2O always produced a seal against a column of fluid in the mouth exerting a hydrostatic pressure of 5.4--8.8 cm H2O against the cuff. This seal was maintained during the whole test period. No difference in sealing capacity was found when the cuff was used with a normal respiratory frequency (20/min) and with high-frequency positive-pressure ventilation (60/min). When the PEEP is eliminated, e.g., when the respirator is disconnected for suction of the endotracheal tube, the sealing effect will be abolished. As the cuff extends up into the larynx there will be no pooling of fluid above the cuff. The risk of aspiration can therefore be diminished by suction of oral cavity before disconnecting the respirator. With the use of the pneumatic valve principle together with high-frequency positive-pressure ventilation, an open respirator system can produce a continuous PEEP, thereby preventing aspiration even during suctioning of the tracheal tube.

Animals↗
PubMed1979

Accumulation of substances with melanin affinity to the internal ear. Therapeutic or ototoxic mechanism?

The capacity of the melanin in the internal ear to accumulate and retain labelled lidocaine, bupivacaine and chlorpromazine after intravenous and intraperitoneal injection was examined by whole-body autoradiography. Both young pigmented hooded rats and albino rats were studied. In the pigmented rats chlorpromazine showed the greatest accumulation, which was more pronounced in the cochlea than in the vestibular portion. The other two substances were evenly distributed in the internal ear. After a single injection of chlorpromazine and of bupivacaine these substances were still bound to the melanin of the internal ear after 14 days, which was the longest survival time. Lidocaine, on the other hand, had disappeared after only 4 days. In albino animals there was very weak, transient uptake of chlorpromazine and bupivacaine, but not of lidocaine, in the internal ear. In studies in vitro on isolated bovine eye melanin there was considerably greater adsorption of chlorpromazine than of lidocaine and bupivacaine.

Animals↗
PubMed1979

Melanin capacity to accumulate drugs in the internal ear. A study on lidocaine, bupivacaine and chlorpromazine.

The distribution and retention of labelled lidocaine, bupivacaine, and chlorpromazine to melanin in the internal ear after intravenous and intraperitoneal injection were examined by whole-body autoradiography. Both young pigmented hooded rats and albino rats were studied. In the pigmented rats chlorpromazine showed the greatest accumulation, which was more pronounced in the cochlea than in the vestibular portion. The other two substances were evenly distributed in the internal ear. After a single injection of chlorpromazine and of bupivacaine these substances were still bound to the melanin of the internal ear after 14 days, which was the longest survival time. Lidocaine, on the other hand, had disappeared after only 4 days. Strong uptake and retention of the three substances were observed in the eyes of pigmented animals. In albino animals there was very weak, transient uptake in the internal ear of chlorpromazine and bupivacaine, but not of lidocaine. In studies in vitro on isolated bovine eye melanin there was considerably greater adsorption of chlorpromazine than of lidocaine and bupivacaine. An uptake was noted in the human eye in experiments in vitro. Clinical tests revealed no acute or late damage to hearing or sight after large doses of lidocaine. The participation of melanin in different basal labyrinthine functions such as the energy transfer mechanism and the sound protective mechanism is discussed in the light of the results obtained. Further, the theory is put forward that the melanin affinity of certain substances can be of both therapeutic and ototoxic importance.

Animals↗
PubMed1977

Physiologic evaluation of the HFPPV pneumatic valve principle and PEEP. An experimental study.

In experiments in dogs the ventilatory and circulatory conditions prevailing with the ventilatory pattern in high-frequency positive-pressure ventilation (HFPPV) were investigated with use of a pneumatic valve principle and a ventilator system of an "open" character. Keeping the gas input constant the importance of insufflation frequency and insufflation time and the reactions to various levels of positive end-expiratory pressure (PEEP) were investigated in terms of changes in arterial pH, Pco2 and Po2. With the volumes of delivered gas kept constant, an increasing insufflation frequency from 60 to 100 per min gave a parallel decrease in tidal volume accompanied by lower maximum intratracheal pressures and a significant decrease in alveolar ventilation. Also taking into account the possibilities of inducing a suppression of the spontaneous respiration, higher ventilatory frequencies than 60 per min do now seem to introduce any further advantages. Including the associated effects on cardiac output and venous admixture, the cardio-pulmonary and circulatory parameters studied did not show any substantial changes with PEEP levels below 7.5--10 cm H2O. Thus the level of PEEP, which often is part of the ventilatory pattern in HFPPV, does not seem to have any untoward influence on the circulation (stroke volume, cardiac output, total peripheral vascular resistance) and oxygen transport (arterial oxygen content and oxygen flux) in normovolaemic dogs.

Animals↗
PubMed1976

Relation between erythrocyte and plasma lithium concentrations as an index in psychiatric disease.

In longitudinal and transverse studies, lithium was measured in plasma, serum and red blood cells (erythrocyte) of healthy male and female subjects as well as in patients of both sexes suffering from manic-depressive disease or schizophrenia. The results confirm that lithium in erythrocytes is lower than in plasma in all groups. The lithium concentration gradient between plasma and erythrocytes is not caused by a slow rate of diffusion through the erythrocyte membrane. The new result of the present study is the importance of sex, disease and age on the erythrocyte/plasma lithium ratio, which is significantly higher in female subjects with manic-depressive disease. This difference persists even during long-term lithium therapy. Older female schizophrenics also have a higher ratio of erythrocyte to plasma lithium than males of the same age. The findings emphasize the importance of endocrine investigation in mental disease and support the view that plasma lithium in humans does not always reflect the intracellular levels. The erythrocyte plasma ratio may also be of value in revealing diagnostic subgroups within the classical psychiatric framework.

Adult↗