Takafumi Yamano

OTotoxicity Of Povidone-Iodine Applied To The Middle Ear Cavity Of Guinea Pigs

OBJECTIVE Povidone-Iodine preparation is used as a disinfectant in otological surgeries. The ototoxicity of Povidone-Iodine preparation was evaluated using infant, young and adult guinea pigs. The effects of different concentrations and of different exposure durations on compound action potentials were also studied. MATERIALS & METHODS Povidone-Iodine was used to fill one middle ear cavity of the guinea pig, and the compound action potential (CAP) was measured from the round window membrane at 24h, 7 days, and 28 days. The contralateral side was filled with saline as control. Test sounds used were clicks and tone bursts of 2, 4, and 8 kHz. RESULTS At 24h, Povidone-Iodine solution showed a significant toxic effect in the infant group. In the young animal group, no toxic effect was seen. In the adult group, a mild degree of deafness for 2 kHz was found. At 7 days, the young group showed significant hearing loss for all frequencies, but the adult group did not show any hearing loss. With a half strength solution, both young and adult group did not show hearing loss. At 28 days, with a full strength solution, hearing loss became prominent for all sound stimulation. With 1/8th dilution, the young group showed a moderate hearing loss, but the adult group did not. CONCLUSION The thicker round window membrane in human is expected to provide more protection to the human cochlea than in the guinea pig model that we have studied. Mild hearing loss at 24h and 7 days using 10% solution, but no hearing loss with 5% solution at 7 days may indicate that rinsing of the middle ear cavity with saline during surgery should minimize the ototoxic effect of this product. The age of the animals does influence the outcome of the ototoxicity experiment. From this experiment, Povidone-Iodine preparations in the infant should be used with caution. Povidone scrub should not be used for otologic surgery.

Ototoxicity of Burow solution on the guinea pig cochlea.

PURPOSE OF THE STUDY The aim of the present study was to evaluate the ototoxicity of Burow solution. PROCEDURES Compound action potentials (CAPs) of the eighth nerve were measured before and 30 minutes after the application of the Burow solution in the middle ear cavity. RESULTS Use of the original Burow solution (pH 3.5) for 30 minutes caused a significant reduction of click sounds. A 2-fold diluted Burow solution (pH 4.4) for 30 minutes caused no reduction in CAP threshold. Burow solution, pH adjusted to 4.5, caused no changes in CAP threshold at 30 minutes. At 24 hours, Burow solution (pH 3.5) caused complete abolition of CAP. CONCLUSIONS Burow solution is ototoxic in the guinea pig when applied in the middle ear cavity for 30 minutes or longer. In the clinical settings, it is advisable to avoid allowing the solution to contact the round window for extended times.

A comparison between the feeling of ear fullness and tinnitus in acute sensorineural hearing loss

The feeling of ear fullness (FEF) occurs frequently in patients with acute sensorineural hearing loss; the same is true for tinnitus (TIN). However, the cause of FEF in these patients is unclear. This study included 171 ears of patients admitted with unilateral sudden deafness to the ENT division of Fukuoka University Hospital between January 2001 and December 2004. The results showed TIN was mainly associated with worse high-frequency hearing thresholds, where hearing loss was relatively severe, and this association became stronger after the hearing threshold stabilized. FEF was associated with the low-frequency region, where hearing loss was relatively mild, and this association disappeared after the hearing threshold stabilized. In conclusion, TIN is thought to originate in the region where hair cells are impaired; in contrast, FEF may originate from some functional factor rather than an organic lesion of the cochlea.

Advantage of early induction of opioid to control pain induced by irradiation in head and neck cancer patients

OBJECTIVE Although radiotherapy is effective for head and neck cancer patients, the local pain evoked by the irradiation itself reduces food intake and frequently halts the treatment. Thus, pain control is an important problem in radiotherapy for head and neck cancer. We performed to examine whether early induction of low-dose, opioid from mild pain improves dietary and caloric intake, while reducing weight loss. METHODS The subjects were 43 patients who were hospitalized for head and neck cancer from 2004 to 2008. They were patients who underwent radiation treatment but those who did not undergo preoperative treatment. They were divided into two groups, depending on whether the pain was mild or moderate when an opioid was introduced (MILD and MODERATE, N=23 and 20, respectively). RESULTS The visual analog scale scores for pain were significantly lower in the MILD than in the MODERATE group at between 25 and 50 Gy. The amount of oxycodone used for pain was significantly lower in the MILD than the MODERATE group. A regular diet was maintained for significantly longer in the MILD group. Caloric intake was significantly higher in the MILD group at over 20 Gy. Weight loss was significantly lower in the MILD group at over 20 Gy. The incidence of side effects was equal in both groups. CONCLUSION Our results indicated that the introduction of opioids for mild pain during radiotherapy controls the level of pain, improving food intake in head and neck cancer patients.

Air pressure-sensing ability of the middle ear-Investigation of sensing regions and appropriate measurement conditions

OBJECTIVE To study the association between ear diseases and the ability of the middle ear to sense air pressure changes, we elucidated the appropriate conditions for measurements and confirmed the pressure-sensing regions while quantitatively assessing the pressure-sensing ability of normal ears and of ears with traumatic perforation of the tympanic membrane. METHODS In 318 normal ears (159 volunteers), an air pressure of 40daPas(-1) was loaded on to the external auditory canals to measure the minimum pressure sensed by subjects as a result of air pressure changes. The minimum pressure was defined as the minimum sensory threshold for air pressure loading (MSTAP; daPa). In 40 of 318 normal ears (20 volunteers), the MSTAP was measured at 10daPas(-1). Next, topical anesthesia was administered to 5 normal ears (5 volunteers), and the MSTAP was measured. In 7 ears with traumatic tympanic membrane perforation (7 cases), the MSTAP was also measured at the first medical examination. The data were analyzed using Stat View 5.0 (SAS Institute Inc., Cary, NC, USA). To test the significance of the data, the Mann-Whitney U-test and the Wilcoxon test were used. RESULTS The mean (+/-S.D.) MSTAP at 40daPas(-1) was -39.2+/-12.2daPa with negative pressure and 39.5+/-12.4daPa with positive pressure. At 10daPas(-1), the MSTAP was -70.3+/-25.0daPa with negative pressure and 72.5+/-22.7daPa with positive pressure, and both the mean and S.D. values were higher than those obtained at 40daPas(-1). Briefly, the MSTAP at 40daPas(-1) produced less variance than that at 10daPas(-1). The MSTAP demonstrated gender- and age-related variations. Moreover, it increased after topical anesthesia was administered to the tympanic membrane. The MSTAP in patients with traumatic tympanic membrane perforation was -205.0+/-26.3daPa with negative pressure and 206.0+/-26.7daPa with positive pressure, and was significantly higher than that observed in case of normal ears. CONCLUSION For obtaining accurate measurements while estimating the pressure-sensing ability of the middle ear, the rate of pressure loading should be considered. Although we assume that the middle ear has pressure-sensing regions other than the tympanic membrane, we conclude that the tympanic membrane is the most sensitive pressure-sensing region in the middle ear.

Ototoxicity of Gentian Violet on the Guinea Pig Cochlea

Purpose Gentian violet (GV) is an antimicrobial and antifungal agent that has been used widely to treat intractable discharge in the ear. The purpose of this report is to warn clinicians about the ototoxic effect of GV in the middle ear. Materials and Methods GV ototoxicity was evaluated by measuring compound action potentials (CAPs) in the VIIIth nerve in adult Hartley guinea pigs. The middle ear cavities of the animals were filled with GV solution (0.5% or 0.13%), and CAPs were measured after intervals of 5 and 30 minutes and 1, 2, 6, and 24 hours. After all measurements were completed, the temporal bones were harvested for histopathologic evaluation. Celloidin-embedded specimens were cut into 20-&mgr;m slices and examined using light microscopy. The bacteriostatic activity of GV was evaluated using a disk-diffusion assay. Results A 0.5% GV solution produced a mild elevation in the CAP threshold at 30 minutes, a greater reduction at 1 hour, and complete abolishment of CAP at 24 hours. A 0.13% GV solution caused mild elevation in the CAP threshold at 2 hours and severe elevation at 6 hours. Massive new bone formation was found in the middle ear cavity at 6 weeks. GV concentrations of 0.13% and 0.06% were effective against all bacteria tested, with the exception of Pseudomonas aeruginosa. Conclusions Although GV has marked antibacterial and antifungal activities, its use should be limited to the external ear canal. GV exerts an ototoxic effect in a concentration- and time-dependent manner, and so the use of this drug in the middle ear cavity is not recommended.

Chronological changes in the eighth cranial nerve compound action potential (CAP) in experimental endolymphatic hydrops: the effects of altering the polarity of click sounds

Conclusion: Using a guinea pig model of experimental endolymphatic hydrops, click sounds of altered polarity showed different latencies and amplitudes in hydropic compared with normal cochleae. Latency changes appeared as early as 1 week after endolymphatic obstruction. This method can help diagnose endolymphatic hydrops. Objective: The goal of the study was to develop an objective electrophysiological diagnosis of endolymphatic hydrops. Materials and methods: Endolymphatic hydrops were created surgically in guinea pigs. The latency and the amplitude of the eighth cranial nerve compound action potential (CAP) for click sounds of altered polarity were measured up to 8 weeks after the surgery. Results: At early stages after surgery, the latency for condensation clicks became longer, and at later stages the latencies for both condensation and rarefaction became longer. The discrepancy in the latencies for rarefaction and condensation click sounds (rarefaction minus condensation) became larger by the first week after surgery, but no further discrepancy occurred thereafter. Compared with latency changes, amplitude changes in the CAP were rapid and progressive following surgery, suggesting ongoing damage to hair cells.