Reversible Ketamine-Medetomidine Anesthesia in Wild Southern River Otters (Lontra provocax)

The southern river otter (Lontra provocax) is one of the four South American otter species and is considered as Endangered by the IUCN with probably the smallest distribution of any otter in the world. The objective of the present study is to describe and assess the use of the reversible ketamine-medetomidine-atipamezole anesthetic combination in southern river otters. Between January and April 2004, four anesthetic procedures (two captures and two surgeries) were performed in three different individuals in cooperation with the River Otters of Chile Project, for radiotransmitter implantation purposes. Anesthesia consisted in ketamine 6 mg/kg (SD ± 2.8) and medetomidine 48 μg/kg (SD ± 10) i.m., reversed with atipamezole 263 μg/kg (SD ± 99) i.m. Initial effect time, latency period and reversal time were recorded. Anesthetic parameters (sonorous stimuli answer, pedal reflex, jaw relaxation and general attitude) and physiologic parameters (rectal temperature, cardiac and respiratory rate, capillary refill time and relative oxyhemoglobin saturation), were monitored at 5-min intervals for 30 min. Anesthetic induction was rapid and smooth with a successful antagonism by atipamezole. Decrease of rectal temperature reached 36.3oC (SD ± 0.5) at 30-min post-anesthetic administration. Cardiac rate was depressed with a mean of 85 beats/min (SD ± 22) and relative oxyhemoglobin saturation (two anesthetic procedures) had an average of 87% (SD ± 12). The anesthetic quality was classified as excellent, based on the anesthetic parameters. Finally, the anesthesia was effective and can be recommended for the capture and surgical radiotransmitter placement on wild L. provocax individuals. However, caution must be taken with possible bradycardia and hypothermia states.