Study of the effects and mechanisms of general anesthesia on cochlear mechanics in domestic pigs: comparison between propofol and isoflurane

• Grant number: 23/14586-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: May 01, 2024
• End date: April 30, 2028
• Field of knowledge: Health Sciences - Speech Therapy
• Principal Investigator: Renata Mota Mamede Carvallo
• Grantee: Diego da Silva Ormundo
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Introduction: Several aspects of cochlear mechanics require experimental studies to be clarified. Thus, domestic pigs have become an excellent model in auditory sciences, as they present anatomical, physiological and genetic aspects suitable for simulating human pathophysiological mechanisms. However, some anesthetics used in animal experiments can alter the nonlinear mechanisms of the cochlea. Principal Objective: To investigate the effects and mechanisms of general anesthesia on the cochlear mechanics in domestic pigs. Specific Objectives: (I) To analyze how propofol and isoflurane alter cochlear amplification and compression; (II) To analyze which mechanisms related to propofol and isoflurane affect cochlear amplification and compression. Hypotheses: It is believed that cochlear mechanics will be reduced mainly with isoflurane and with the time of exposure to this anesthetics. It is also believed that the mechanisms involved are: (1) reduction of the cochlear blood flow, directly altering the functioning of the cochlea and/or (2) alterations in the middle ear, directly affecting the responses coming from the cochlear mechanics. Method: Randomly, the animals will be allocated to the Propofol Group (PG) or the Isoflurane Group (GI), resulting ten animals in each group. Cochlear mechanics will be evaluated with the DPOAE test. To estimate cochlear blood flow, systemic Mean Arterial Pressure will be measured by accessing the femoral artery. To evaluate the middle ear, Acoustic Immittance Measurements will be performed. All measurements will be recorded in four 15-minute stages, which, respectively, will begin 40 minutes, 55 minutes, 70 minutes and 85 minutes after the start of anesthesia. Relevance: In practical terms, this study may contribute to the development of experimental protocols, as well as to the refinement of experimental models with domestic pigs in hearing sciences. In theoretical terms, it will bring new understandings regarding the physiology of the peripheral auditory system, since this theme leads us to discussions related to cellular, vascular and neural aspects of the cochlea and middle ear. Considerations: This study is motivated by the interest in refining protocols with domestic pigs in hearing sciences. In addition, it brings new understandings regarding the physiology of the peripheral auditory system.