Biomedical subjects
Publications and source records attributed to E Hultcrantz.
The effect of noise and unilateral transection of the cervical sympathetic trunk on cochlear blood flow was studied in anesthetized cats. The sound pressure level was 100 dB and the exposure time 6 min. Neither noise nor sympathectomy were found to affect the blood flow.
The cochlear blood flow was studied with the microsphere method in guinea pigs, rats and cats. Results from experiments using different sizes of microspheres were compared and the effect of middle ear infection or perforation of the otic capsule on the cochlear microcirculation was investigated. Neither the opening of the cochlear bony wall nor the middle ear infection influenced the blood flow in the cochlea. 9- and 15-micrometer spheres were given simultaneously and the results were equivalent, indicating no more shunting of the smaller ones than of the bigger ones. Thus, the smaller spheres are to be preferred, since the smaller ones can be used in a larger number without negative effects on the general circulation. In cats, the cochlear blood circulation was determined before and during cervical sympathetic stimulation. Sympathetic stimulation caused a reduction of 25% of the cochlear blood flow.
The effect of hemodilution on cochlear blood flow was studied in guinea pigs. Hypervolemic hemodilution was accomplished by infusion of 10 mg/kg of body weight of dextran 40 (as a 10% solution in normal saline), which resulted in an average hematocrit decrease from 43 to 32%. Normovolemic hemodilution was accomplished by repeated exchange of 3 ml of whole blood with 3 ml of dextran 75 (6% solution in normal saline) every 5 minutes until the hematocrit reached approximately 5%. The cochlear blood flow was measured by laser-Doppler flowmetry. Irrespective of the dilutional technique, the cochlear blood flow increased as hematocrit decreased to a maximum of approximately 200% of original value at a hematocrit near 20%. The blood pressure was not significantly influenced by the hemodilution until hematocrit values below 15% were reached. The enhancement of cochlear blood flow is consistent with the expected reduction of blood viscosity and increase of cardiac output. Normovolemic hemodilution with dextran 75 causes a smaller disturbance of systemic circulation physiology and has a more lasting effect than dextran 40 infusion.
A multitude of general disorders of the vascular system may also affect the blood circulation of the cochlea and cause symptoms such as fluctuating or permanent hearing loss. Such is the case for arteriosclerosis combined with hypertension or hypotension, collagenosis, and diabetes. Blood disorders, like leukemia, sickle cell anemia, and polycythemia, and infectious diseases involving the blood vessels, such as lues, may also present their primary symptoms in the ear. The otorhinolaryngologist must be able to establish the correct diagnosis and refer patients requiring more general treatment to other specialists. The use of specific vasoactive treatment should be continued to those patients with symptoms of acute or fluctuating hearing loss, vertigo, or tinnitus who exhibit no other signs. Modern techniques for cochlear blood flow measurements have verified that several of the treatment protocols in use, which have a sound theoretical background, do indeed increase cochlear blood flow.
A retrospective evaluation was performed in 112 patients treated during a 10-year period as inpatients with the diagnosis idiopathic sudden hearing loss. Excluding all patients in whom later other diagnosis were established, like Ménière's disease, collagenoses, mumps etc., 101 patients remained. 80 of them had been treated consistently according to a protocol as having idiopathic sudden hearing loss. These patients had all 5-day treatment with low molecular weight dextran and nicotinic acid and vitamin B during 1 month. 68% did completely recover or were markedly improved (> 30 dB), another 19% were fairly improved (10-30 dB). Statistical analysis showed that all retrocochlear signs or nystagmus made the prognosis less favorable. To wake up with the hearing loss was more favorable than a daytime debut. A mid-frequency loss had always a good prognosis. Because no untreated controls were included in the study, it was not possible to evaluate the specific effect of the treatment. The results obtained from this study have changed the treatment policy in our clinic.
Cochlear blood flow in the guinea pig was investigated using Tracer Sephadex 15 microspheres labelled with radioactive nuclides. A reference organ technique was used for quantitative measurements of cardiac output and the blood flow in the cochlear soft tissue, CNS and kidney. In some experiments the blood flow was measured at two occasions, either with 57Coor with 58Co-labelled microspheres. The results, including the size of cochlear blood flow are presented and discussed.
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The purpose of this study was to examine the electrophysiologic responses to sound from guinea pig cochleas, 3--6 days after a unilateral cervical sympathectomy. After recovery from surgery the guinea pigs developed a Horner's syndrome on the sympathectomized side. Some days later their bullas were opened and electrodes were placed bilaterally on the round windows. Most of the sympathectomized cochleas showed signs of decreased sensitivity to sound. They had a smaller dynamic range for the click- and tone-burst evoked compound action potential (CAP) compared with the non-sympathectomized cochleas. The threshold sound levels for the CAPs and the sound levels to produce 1 muV of cochlear microphonic potentials were unaffected. In other animals with chronic implanted electrodes, the same electrical responses were measured with only light sedation before and after sympathectomy and showed the same results. In additional animals the crossed olivocochlear bundle (COCB) was electrically stimulated and a similar inhibition of the CAP was registered on both the intact and the sympathectomized side. The results suggest that the sympathetic nerves to the cochlea, coming from the ipsilateral cervical ganglion and ending near the habenula perforata, may be important for the sound perception as they influence the CAP.
Cochlear blood flow was studied with the microsphere method in young and old normotensive and spontaneously hypertensive rats. The young animals were 3-6 months old and the old ones 18-24 months. The cochlear blood flow in young rats was 1.64 microliter/min/cochlea for the normotensive and 1.51 for the spontaneously hypertensive rats. In the old rats, the cochlear blood flow rates were 1.40 and 1.29 microliter/min/cochlea, respectively. The differences were not significant between the age groups, nor between the normotensive and spontaneously hypertensive rats. However, there was a tendency towards lower cochlear blood flow with increasing age, especially among the spontaneously hypertensive rats. The difference between young normotensive and old spontaneously hypertensive rats was significant (p less than 0.05). The group of old hypertensive rats was also the only one with evident morphological changes in the organ of Corti.
Cochlear blood flow was measured in rats with a known noise-induced hearing loss, using the microsphere technique. The animals were exposed to simulated industrial noise for 3 months. The rats were divided into four groups: young and old; normotensive (N) and spontaneously hypertensive (SH). The mean values of the cochlear blood flows were compared with those of rats from matched groups not exposed to noise. The mean cochlear blood flow in the noise-exposed groups was lower than in the non-exposed groups. The decrease in cochlear blood flow was significant for all groups except young SH rats and was more pronounced in the older age group. Cochleas from the groups of old N and SH rats were investigated in the scanning electron microscope. Extensive changes were far more common in SH than in N rats.