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 a Ketamine/Dexmedetomidine as a reversible chemical restraint 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 (male n = 8; females n = 10) (67.3 ± 9.45 kg), prior to chemical restraint, were physically confined, subsequently darted intramuscularly with 9 mg kg-1 ketamine and 0,005 mg kg-1 dexmedetomidine. Post-intervention, 0,005 mg kg-1 atipamezole, administered IM, was used as a reversal agent (RA), (n = 5). Anesthetic effects were recorded as latency period (LP I/first observed effects) (LP II /lateral recumbency plus time to handle the animal). Recovery time was divided into (R1/no RA, fully recovered/ready for release), (R2a/R2b, with RA, time to ambulant position plus time to full recovery/release, respectively). Vital signs were recorded at a 15-minute interval. GraphPad Prism 8.1.1 was used to perform unpaired t-test, with a p-value ˂ 0,05 considered significant. Results: Mean LP I: 3 ± 1 min.; LP II: 10 ± 2 min. Procedure duration: 49 ± 5 min. Recovery time without RA, (R1): 55 ± 15 min., compared to 18 min., with RA (R2a) to ambulant position (with severe discoordination), requiring additional time until full recovery (ready for release): ± 45 min (R2b). Total time, to release (R2a/b): mean ± SD = 67 ± 13.85 min. Concluding for clinical relevance that the association of Ketamine and Dexmedetomidine performed satisfactorily, providing effective sedation and analgesia, and relative short latency periods. Used RA did not shorten total recovery time significantly (P-value = 0,7328). 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 induced bradycardia/hyperthermia warrant extra caution. The employed RDDS provided reliable drug delivery under field conditions.

Keywords

• rdds, wildlife chemical restraint, atipamezole, capybara.