Inhalation anesthesia in Dumeril's monitor (Varanus dumerili) with isoflurane, sevoflurane, and nitrous oxide:: Effects of inspired gases on induction and recovery

Induction and recovery from inhalation anesthesia of Dumeril's monitors (Varanus dumerili) using isoflurane, sevoflurane, and nitrous oxide (N2O) were characterized using a randomized crossover design. Mean times to induction for isoflurane in 100% oxygen (O-2), sevoflurane in 100% O-2, sevoflurane in 21% O-2:79% nitrogen (N-2; room air), and sevoflurane in 66% N2O:34% O-2 were 13.00 +/- 4.55, 11.20 +/- 3.77, 10.40 +/- 2.50, and 9.40 +/- 2.80 min, respectively, at 26 degrees C (n = 10). Mask induction with sevoflurane was significantly faster than with isoflurane. There was no significant difference between the induction time for sevoflurane in O-2 or in room air, but sevoflurane combined with N2O resulted in significantly faster inductions than were obtained with sevoflurane in 100% O-2. All treatments resulted in a significantly higher respiratory rate than in undisturbed animals. There were no significant differences in respiratory rate among lizards receiving O-2, isoflurane in 100% O-2, sevoflurane in room air, and sevoflurane combined with N2O, but animals receiving sevoflurane in O-2 had a lower respiratory rate than those receiving pure O2. The sequence of complete muscle relaxation during induction was consistent and not significantly different among the four treatments: front limbs lost tone first, followed by the neck and the hind limbs; then the righting reflex was lost and finally tail tone. There were no significant differences in recovery times between isoflurane and sevoflurane or between sevoflurane in 100% O-2 and sevoflurane combined with N2O. Similar recovery times were observed in animals recovering in 100 and 21% O-2.