Chemical immobilization of free-living capybaras (Hydrochoerus hydrochaeris) using ketamine-dexmedetomidine combination and a remote drug delivery system

Abstract

Capturing wild capybaras for scientific projects, population control or medical interventions is a growing necessity. With this study, we intended to evaluate the association Ketamine/Dexmedetomidine (KD) as a reversible chemical restraint protocol in free-ranging synanthropic capybaras, seeking enhanced anesthetic and recovery characteristics while testing a specialized remote drug delivery system (RDDS). For this purpose, 18 adult capybaras (eight males, ten females) with a mean bodyweight of 67.3 ± 9.45 kg were used. Prior to chemical restraint, the animals were physically confined, subsequently darted intramuscularly (IM) with 9.9 mg/kg ketamine with 0.0005 mg/kg dexmedetomidine. Post-intervention, 0.005 mg/kg atipamezole, administered IM, was used (n=5) as a reversal agent (RA). Anesthetic effects were classified and recorded as LP1 - latency period one (first observed effects). LP2 - latency period two, lateral recumbency, plus apt-time (able to handle animal). R1 - total recovery period one, no RA. R2, subdivided in R2a - partial recovery period one, ambulant position/but with incoordination, and R2b - partial recovery period two, time to full recovery (with RA). Vital signs were recorded at a 15-minute interval. Results: Induction time LP1: 3 ± 1 min and LP2: 10 ± 2 min. Procedure duration: 53 ± 25 min. (sedated). Recovery time R1: 55 ± 15 min. R2a: 18 min., RA2b: ± 45 min., total recovery time (R2a/b): 67 ± 13.85 min. Conclusion: KD association provided excellent sedation, analgesia, and muscle relaxation, with a relative short induction time. Used RA did not shorten total recovery time significantly. Adverse effects such as the risk of acute cecal tympany, due to the lack of pre-anesthetic fasting, concurrent to collateral effects of injectable and volatile anesthetics on the motility of the digestive tract, and potential for induced bradycardia/hyperthermia warrant extra caution. The employed RDDS performed satisfactorily under field conditions.