Isoflurane, sevoflurane and desflurane use in cane toads (Rhinella marina)

Abstract

Anaesthetic chamber concentrations of isoflurane, sevoflurane and desflurane that resulted in loss of righting reflex within 15 minutes in 50 per cent of toads (Rhinella marina) exposed (ED50-LRR<15MIN) were identified. The median and range ED50-LRR<15MIN was 1.4 (0.9-1.4) per cent for isoflurane, 1.75 (1.1-1.9) per cent for sevoflurane and 4.4 (4.3-5.5) per cent for desflurane. Subsequently, toads were exposed to 1.5 times the ED50-LRR<15MIN and times to loss and return of righting reflex were identified. All toads for all anaesthetics lost righting reflex. The median and range loss of righting reflex was 4:00 (3:00-5:30) minutes for isoflurane, 4:45 (3:30-7:00) minutes for sevoflurane, and 4:15 (4:00-5:30) minutes for desflurane and was not different between anaesthetics. Time to return of righting reflex was 175 (123-211) minutes for isoflurane, 192 (116-383) minutes for sevoflurane and 74 (52-220) minutes for desflurane. Time to return of righting reflex was significantly shorter for desflurane compared with isoflurane or sevoflurane. The use of isoflurane, sevoflurane or desflurane can be used to provide immobilisation to cane toads and potentially other anurans. Induction times are likely similar when using an anaesthetic chamber to provide anaesthesia. However recovery time may take twice as long when utilising isoflurane or sevoflurane over desflurane.