01.04.2020: Medical interventions under anaesthesia are a common necessity not only in humans but also in non-domestic mammals. However, the anaesthetic drug combinations currently used often lead to undesirable side effects, such as severe hypertension. A new drug now promises to improve anaesthetic safety in wildlife anaesthesia, as a recent study by the Research Institute of Wildlife Ecology at Vetmeduni Vienna shows.

High blood pressure and a low heart rate are major problems during anaesthesia of non-domestic animals. These known side effects of a group of alpha-adrenergic agonists that are commonly used in high doses in combination with other anaesthetic agents in wildlife anaesthesia.

An international team of researchers from the Research Institute of Wildlife Ecology, the Clinical Unit of Anaesthesiology and Perioperative Intensive-Care Medicine at Vetmeduni Vienna, and from the University of Helsinki therefore investigated the effects of vatinoxan on cardiovascular parameters in red deer (Cervus elaphus). Vatinoxan, a novel drug developed at the University of Helsinki, is designed to reverse the undesirable cardiovascular effects of alpha-adrenergic agonists without affecting their desired anaesthetic and analgesic effects.

Improving anaesthetic safety in non-domestic animals

“The results showed that vatinoxan successfully reduced elevated blood pressure and temporarily increased heart rate without significantly influencing the desired depth of anaesthesia,” says principal investigator Gabrielle Stalder from the Research Institute of Wildlife Ecology at Vetmeduni Vienna. Specifically, the intravenous administration of vatinoxan alleviated cardiovascular side effects such as hypertension and bradycardia in deer anaesthetized with the drug combination medetomidine-tiletamine-zolazepam. Vatinoxan had no significant effect on the depth of anaesthesia and did not impair reversal of sedation by atipamezole in the wake-up phase. “The improved cardiovascular function induced by vatinoxan has the potential to improve anaesthesia safety and reduce anaesthetic side effects in anaesthetized non-domestic mammals,” Stalder added.

Vatinoxan significantly better than saline

To evaluate the effect of vatinoxan, a combination of 0.1 mg of medetomidine and 2.5 mg of tiletamine-zolazepam were administered intramuscularly to the deer per kilogram of live weight, followed by the intravenous administration of 0.1 mg per kilogram of vatinoxan or an equal volume of saline 35 minutes after induction. Heart rate, direct arterial blood pressure, respiratory rate, arterial oxygen saturation, concentration of CO₂ in exhaled air, rectal temperature and depth of anaesthesia were assessed before administration of vatinoxan (drug treatment) or saline (control) and then measured at five-minute intervals.

Fewer side effects despite high drug dosage

Chemical immobilization and anaesthesia are often essential for medical interventions in wildlife species. However, the induction and maintenance of balanced anaesthesia by injectable anaesthetics often requires high doses of alpha-adrenergic agonists drug combinations. This can result in severe hypertension and bradycardia in non-domestic mammals such as the red deer examined in this study. The drug vatinoxan offers a solution to this problem in wildlife anaesthesia.

The article “Cardiovascular effects of intravenous vatinoxan (MK-467) in medetomidine-tiletamine-zolazepam anaesthetized red deer (Cervus elaphus)” by Joy Einwaller, Johanna Painer, Marja Raekallio, Kristina Gasch, Flavia Restitutti, Ulrike Auer & Gabrielle Stalder was published in Veterinary Anaesthesia and Analgesia.