Influence of pre-anesthetic acclimatization and seasonality on the Minimum Anesthetic Concentration (MAC) of Sevoflurane in Green Iguanas (Iguana iguana)

• Grant number: 23/01363-1
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: July 01, 2023
• End date: February 28, 2027
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Clinics and Surgery
• Principal Investigator: Adriano Bonfim Carregaro
• Grantee: André Augusto Justo
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

Green iguanas (Iguana iguana) are frequently admitted at veterinary referral centres and used as experimental models for studies investigating the biology of lizards, so that inhalantional anesthesia is a common modality for surgical and diagnostic procedures in this species. The minimum anesthetic concentration (MAC) measures the concentration that an inhalant anesthetic requires for allowing an adequate surgical anesthetic depth in lizards, though there is major variation in the MAC values reported in the literature in this group of reptiles. Body temperature is one of the factors that alter MAC; thus, because they are ectothermic animals, the role of ambient temperature on the metabolism of lizards, and hence, on the MAC of inhalant anesthetics is up for debate. This study aims to determine the influence of preanesthetic acclimatization and seasonality on the MAC of sevoflurane in green iguanas. Both in winter and summer, the MAC of sevoflurane will be established in eight animals submitted to three different environmental conditions: after three months indoors (temperature, photoperiod and humidity controlled), after three months outdoors (temperature, photoperiod and humidity not controlled) and after 3 months outdoors and following a 24-hour periodindoors. The MAC will be determined by the bracketing method. For each positive response, the fraction of expired sevoflurane will be increased by 10% and, for each negative response, it will be reduced to the same extent. The MAC of the animal will be represented by the mean of the values obtained in two crossover events, while the general MAC will be represented by the mean of the animals' MAC. It is expected that, for the same season of the year, there will be great intra-individual variability between estimates of MAC, that is, that the sevoflurane MAC varies according to the husbandry the iguanas had been submitted to despite undergoing anesthesia within optimal temperature ranges. Furthermore, it is expected that the MAC in the summer is consistently higher than that obtained in the winter in all methods of pre-anesthetic acclimatization, since the animals' metabolism is higher in the summer even under controlled environmental conditions. (AU)