Achieving Cochlear Therapeutic Hypothermia through Irrigation of the Mastoid and Tympanic Cavities.

INTRODUCTION: Mild therapeutic hypothermia (MTH) is an exciting nonpharmaceutical otoprotection strategy. In this study, we applied simple irrigation of the tympanic and mastoid cavities to understand the timing of both achieving MTH and recovery back to euthermic temperatures for application in the clinical setting. METHODS: Three human temporal bones were used in this study in the temporal bone laboratory. A standard mastoidectomy was performed on each followed by the insertion of temperature probes into the basal turn of the cochlea via a middle cranial fossa approach. The temporal bones were warmed in heated bead baths to 37°C. The tympanic and mastoid cavities were then irrigated with room temperature water, and intracochlear temperature readings were recorded every minute. After 15 min, irrigation was stopped, and temperature readings were collected until temporal bones returned to euthermic levels. RESULTS: Intracochlear MTH was achieved within the first minute of irrigating the tympanic and mastoid cavities. Intracochlear temperatures plateaued after 5 min around 30°C. Discontinuation of irrigation resulted in the temperature rising logarithmically above the MTH levels after 9-10 min. CONCLUSION: Intracochlear MTH can be achieved via irrigation of the tympanic and mastoid cavities with room temperature irrigation within 60 s. After irrigation for 5 min, hypothermic temperatures will remain therapeutic for 10 min following cessation of irrigation.

Achieving Mild Therapeutic Hypothermia in the Human Cochlea.

OBJECTIVE: To determine temperature and duration of cooling necessary for achieving cochlear mild therapeutic hypothermia (MTH) via ear canal cooling using cool water and earmold attached to a Peltier device. STUDY DESIGN AND SETTING: Human temporal bone lab study performed at the University of Mississippi Medical Center. INTERVENTIONS: Cochlear cooling via the ear canal using water irrigation and an earmold attached to a Peltier device. Temperature analysis through implanted thermal probes within the cochlea. MAIN OUTCOME MEASURES: Temperature changes in the cochlea. RESULTS: Irrigation of the ear canal with water resulted in achieving MTH in approximately 4 minutes using cool water (30°C) and in approximately 2 minutes using ice-chilled water. After 20 minutes, irrigation of the ear canal using cool water plateaued at a ∆2°C while cooling with ice-chilled water results in an average ∆4.5°C. We observed MTH using a medium-length earmold attached to a Peltier device after approximately 22 minutes of cooling and achieved a maximal average ∆ of 2.3°C after 60 minutes of cooling. Finally, we observed that a longer earmold (C2L) with greater proximity to the eardrum resulted in more efficient intracochlear temperature change, achieving MTH in approximately 16 minutes. CONCLUSIONS: MTH of the cochlea can be achieved with water-based ear canal irrigation and via a Peltier device connected to an aluminum earmold.

In Vitro Comparison Between Ovine and Human Recombinant Hyaluronidase on Hyaluronic Acid Fillers.

Introduction: Injectable hyaluronic acid (HA) fillers are commonly used to provide tissue augmentation and combat the effects of facial aging. Ovine and human recombinant formulations of the enzyme hyaluronidase (HAse) are used interchangeably; however, it is unknown if there exists a difference in their ability to degrade HA. Objective: To compare rates at which ovine and human recombinant forms of HAse degrade various HA fillers in vitro. Methods: Increasing amounts of either ovine or human recombinant HAse were added to fixed amounts of nine unique HA filler products. Degradation rates were then analyzed using a colorimetric method by measuring absorbance levels of degraded product. Results: Human recombinant HAse degraded more HA when compared with ovine HAse overall (p = 0.014, confidence interval [-0.015 to -0.0018]). Conclusions: Human recombinant HAse was found to be more effective on average in degrading HA fillers when compared with ovine HAse in vitro.