A crossover study was performed in 12 Himalayan tahr (Hemitragus jemlahicus) undergoing pre-shipment examinations to compare partially reversible and fully reversible intramuscular anesthesia protocols. The partially reversible protocol (MKA) consisted of induction with medetomidine (0.06±0.009 mg/kg) and ketamine (2.03±0.315 mg/kg), and atipamezole (0.30±0.044 mg/kg) reversal. The fully reversible protocol (CXNA) consisted of induction with carfentanil (0.009±0.003 mg/kg) and xylazine (0.08±0.019 mg/kg) with naltrexone (0.867±0.332 mg/kg) and atipamezole (0.105±0.023 mg/kg) reversal. During immobilization, animals were monitored for quality and length of induction and recovery, heart rate (HR), respiratory rate (RR), rectal temperature (Tr), indirect mean blood pressure (MBP), oxygen saturation (SO2), and end-tidal carbon dioxide (ETCO2). Blood was collected for serum cortisol measurement. No differences were observed for induction time, HR, RR, Tr, SO2, or ETCO2. MKA resulted in significantly higher MBP (137±21 vs. 93±22 mm Hg, p=0.004), higher serum cortisol (6.76±1.39 vs. 4.28±3.69 µg/dL, p=0.007), and longer recovery time (15.67±11.18 vs. 5.00±1.95 minutes, p=0.001) compared to CXNA. More importantly, the quality of induction and recovery was very different. With MKA, animals spent less time ambulating during induction, remained recumbent longer during recovery, and demonstrated more ataxia on rising. Despite differences between the protocols, both were successful and safe. These differences should be taken into consideration when selecting the anesthetic protocol, because either regimen may be more or less desirable for different medical or immobilization settings.
The authors are grateful to the Department of Mammalogy staff and veterinary technicians for their assistance with the procedures, and to David Powell for discussing statistical analysis of the data.