Impact of the number of cross-overs by the bracketing design on the Minimum Anesthetic Concentration (MAC) of sevoflurane in green iguanas

• Grant number: 24/06461-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2024
• End date: May 31, 2025
• Field of knowledge: Agronomical Sciences - Veterinary Medicine
• Principal Investigator: Adriano Bonfim Carregaro
• Grantee: Carolina da Silva Braga
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

The minimum anesthetic concentration (MAC) allows quantifying the concentration of an inhalational anesthetic necessary to maintain an adequate surgical depth, with the bracketing design being the most widespread method for establishing MAC in lizards. In this methodology, the anesthetic concentration is modified over the course of anesthesia with the aim of obtaining cross-overs, in which opposite motor responses to supramaximal nociceptive stimuli are generated following consecutive changes in the anesthetic concentration. However, the bracketing design is known not only for its high failure rate in generating MAC values in herpetofauna, but also for its prolonged anesthetic time. Therefore, refining methods for establishing MAC are necessary when using the bracketing design in this group of animals. This study aims to determine the influence of the number of cross-overs on the MAC of sevoflurane obtained by the bracketing design in green iguanas. To do so, the database of experiments focused on establishing the MAC of sevoflurane in green iguanas will be analyzed retrospectively, as well as animals will be prospectively evaluated to determine the sevoflurane MAC. Four distinct methods for obtaining cross-overs will be considered, namely: an isolated cross-over, two consecutive cross-overs, three consecutive cross-overs and two non-consecutive cross-overs. Individual MAC values will be yielded by the average of the anesthetic concentrations corresponding to each cross-over. It is expected that the MAC of sevoflurane will not be significantly influenced by the number of cross-overs, so that the total time of anesthesia and cost of anesthesia could be optimized in future studies.