Alexandra Thiel, Boris Fuchs, Andrea Miller, David Ahlqvist, Andrea Friebe, Aimee G Tallian, Stamatios Tahas, Jonas Kindberg, Alina L Evans

Hypertension, hypoxemia, hyperthermia and tissue hypoperfusion are reported in brown bears (Ursus arctos) anesthetized with medetomidine-tiletamine-zolazepam (MTZ), with welfare concerns during and after capture. Vatinoxan is a selective peripheral α2-adrenoceptor antagonist known to alleviate the cardiovascular, acid-base and thermoregulatory adverse effects of medetomidine with minimal effect on sedation and analgesia. Following the identification of the optimal doses of vatinoxan in 21 captive brown bears involved in a promising pilot study, a series of double-blinded randomized controlled studies is underway in free-ranging individuals captured and anesthetized in Scandinavia. Such research aims to assess the beneficial and adverse effects of low and high doses of vatinoxan on wild bear physiology during and after capture and anesthesia. Once the bears are captured and anesthetized, a comprehensive physiological dataset, including anesthetic depth, direct blood pressure, heart rate, respiratory rate, tissue oxygen saturation, rectal temperature, arterial and venous blood gases, acid-base status, electrolytes and blood glucose, is recorded at regular intervals in both treatment and control groups. Cardiovascular variables improved dose-dependently within 5 minutes of vatinoxan administration, alleviating hypertension and bradycardia, cephalic and muscle perfusion and blood pH compared to controls. Hyperthermic bears treated with vatinoxan responded to active cooling faster than controls. No effect on the anesthetic depth was detected. Reported occasional adverse effects included hypokalemia, hypoglycemia, transient hypotension and spontaneous defecation, particularly at high doses. While its use requires caution, the preliminary findings of our studies indicate that vatinoxan could play a central role in the treatment of bradycardia, hypertension, hypoperfusion, hyperthermia, and hyperglycemia in wild brown bears anesthetized with MTZ.