Influence of the noxious stimulus and seasonality on the Minimum Anesthetic Concentration of sevoflurane in green iguanas (Iguana iguana)

• Grant number: 22/05391-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2022
• End date: June 30, 2023
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Clinics and Surgery
• Principal Investigator: Adriano Bonfim Carregaro
• Grantee: Laura Roverato Ghussn
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

This study aims to assess if the type of noxious stimulus and seasonality can affect the sevoflurane minimum anaesthetic concentration (MAC) in green iguanas (Iguana iguana). Eight animals, housed under controlled conditions of temperature, photoperiod and humidity, will be undergoing inhalation anaesthesia for the sevoflurane MAC determination in four different moments (n = 8): mechanical stimulus by clamping the base of the tail and an electrical stimulus at 20V, 50Hz, both performed in winter and summertime. Anaesthetic induction will be performed with sevoflurane, in dose-effect, by a face mask and nonrebreathing system. After endotracheal intubation, sevoflurane will be set at a 3% start end-tidal concentration (FE'Sevo), and iguanas will be maintained in mechanical ventilation (5 cmH2O, Insp:Exp 1:2 with a frequency of 4 to 6 breaths/minute). After a period of stabilization of 15 minutes, sevoflurane MAC determination will be stated by the bracketing method. At each physical positive response, the FE'Sevo will be increased by 10% and at each negative response, it will be decreased by the same intensity. The MAC of each animal will be obtained by the mean values of two crossover events, and the sevoflurane MAC will be obtained by the mean values of the group. It will be expected the sevoflurane MAC obtained by electrical stimulus will be higher than the mechanical stimulus, due to the potential local desensitization. Furthermore, it will be expected a difference between the MAC values determined in different seasons of the year, since the animals' metabolic rate is lower in winter, even if the animals if the animals have housed under controlled conditions.