Romifidine HCl as Adjuvant to Dissociative Anesthesia in Big Wild Captive Felids in Brazil
Restraint is the most important limiting factor in wildlife practice.1 A variety of drugs can be used to produce sedation or anesthesia in wild animals. This paper reports the use of romifidine hydrochloride in combination with other drugs, including tiletamine hydrochloride, zolazepam, ketamine hydrochloride, and atropine sulfate to produce field anesthesia in big, wild felids. The objective of this study was to evaluate both the efficacy of the drug combinations and the allometric scaling method of dosage calculation. Romifidine is a highly concentrated alpha-2 adrenoceptor agonist originally produced as a sedative for horses. Romifidine’s use in combination with dissociative anesthetics for the chemical restraint of large wild felids have yielded encouraging results.3-7 Allometric scaling method was recently reviewed,2 and it permits extrapolation of drug doses between animals of different sizes and/or taxa, facilitating the use of data obtained in a “model animal” (animal for which the drug was developed) for the treatment of a “target animal” (wild or domestic patient).
From June 1999 to December 2005 the staff of the Service of Wildlife Medicine of the Universidade Paranaense (Umuarama, PR, Brazil) anesthetized 18 jaguars (Panthera onca), six pumas (Puma concolor), 29 African lions (Panthera leo), and three tigers (Panthera tigris) in several Brazilian zoos, conservation units, and circuses. Jaguars, pumas, and lions were anesthetized with a combination of romifidine, tiletamine, zolazepam, and atropine (RTZA). Tigers were anesthetized with the association of romifidine, ketamine, and atropine (RKA). All doses were established by allometric scaling, using a 10-kg dog and a 500-kg horse as models. Using the dog model, the following doses were used: tiletamine plus zolazepam at 5 mg/kg; ketamine at 10 mg/kg; and atropine at 0.05 mg/kg. Using the horse model, romifidine was administered at 0.08 mg/kg. In all cases the drugs were administered intramuscularly by darts delivered by a blowgun. All patients were subjected to careful monitoring immediately after losing the righting reflex until fully recovered by exhibiting normal ambulation. During anesthesia, physiologic parameters (heart frequency, respiratory frequency, rectal temperature, and SpO2) and response to painful stimuli were monitored every 10 minutes.
Animals anesthetized with both combinations lost the righting reflex (RR) within 2–15 minutes post-injection (MPI), and deep anesthesia occurred in all cases, beginning between 5–18 minutes MPI. All patients showed excellent myorelaxation during the study and remained safely anesthetized for 60–115 minutes MPI. Conscious reactions were noted between 96–170 minutes MPI and the return of the RR was noted between 126-380 minutes MPI. Prolonged recovery (more than 4.0 hours) was observed in three animals (two lions and a puma) and was likely due to cold ambient temperatures (5–8°C degrees centigrade) during the anesthetic procedure. Supplemental heat was not available when the procedure was performed under field conditions. The proposed anesthetic protocols proved to be safe and effective in many medical procedures including physical examination, identification transponder placement, biologic sample collection, declawing, and dental and general surgery.
The results of this study lead the authors to conclude that the use of romifidine in association with dissociative anesthetics is a good option in chemical restraint and field anesthesia of big, wild felids. Its use with tiletamine and zolazepam provided safe and effective anesthesia in jaguars, pumas, and lions. Good results were also obtained in tigers when using romifidine in combination with ketamine. Unfortunately, alpha-2 adrenergic reversal agents such as yohimbine and atipamezole were not available in Brazil during this study. Their use is advocated and will be investigated in future studies with expected decreases in recovery times.
The results of the tested romifidine protocols appear promising for the zoo and wildlife practitioner. Furthermore, allometric scaling proved to be a useful tool for determining a safe initial dose of the anesthetic agents in the wild felids in this study.
The authors thank the zoos, circuses, and conservation units that have called the staff to anesthetize their animals. This research was partially supported by the Research Institute of the Universidade Paranaense—UNIPAR.
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