VN May 2022

Vetnews | Mei 2022 7 A white rhino can be up to 2m tall at the shoulder, and the average male weighs over 2 tonnes – although there are reports of the largest animals reaching 4 tonnes. Their sheer size makes any intervention a problematic proposition. First and foremost, there is the animal’s safety to consider, but each procedure must be safe for people too. To better understand what different immobilising drugs do to an animal and improve the welfare of the animals and reduce the risks during anaesthesia, one needs to evaluate their physiology properly. So how exactly do you collect physiological data from rhino? Once the rhino is immobilised, Leith’s team uses a PowerLab system with transducers adapted from human exercise physiology gear – mainly a gas analyser and spirometer – to monitor the rhino’s ventilation, tidal volume, respiratory rates, and metabolism during anaesthesia. Rhinos are obligate nasal breathers that enable all expired gases to be collected from their nostrils. In place of a face mask, Leith uses adapted equine endotracheal tubes in their nostrils to collect the expired gases, measuring airflow and the CO 2 and O 2 levels each time the rhino breathes out. Calculating VO 2 andVCO 2 from these measures indicates howmuch O 2 the rhino is burning up and howmuch CO 2 they produce. Capture drugs often make the animals hypermetabolic – Leith’s team aims to develop ways to reduce this elevated metabolism. A catheter is inserted into an artery in the rhino’s ear to monitor blood pressure and other variables such as blood oxygenation and pH. Otherdevices,includingapulseoximeterandelectroencephalogram (EEG) monitor, are also placed on the animal to determine blood oxygen levels and the changes in the activity of the brain waves to get a better assessment of the depth of the immobilisation/ anaesthesia. Venous blood samples are also drawn from the cephalic artery to measure some stress and health biomarkers. Leading Article >>> 8 Dr. Peter Buss (Veterinary Senior Manager, Kruger National Park) and Dr. Mathew Ndunda’s (PhD student University of Pretoria, Veterinarian Kenyan Wildife Service) are monitoring and recording the heart rate of the immobilised rhinoceros while Dr Luke Mic aelides (MSc student University of Pretoria) is collecting a blood sample from the cephalic vein for the assessment of the stress response to the drug combination. Chemical immobilisation of a white rhinoceros for a large collaborative study between the University of Pretoria, SANPark’s Veterinary Wildlife Service and researchers from Cornell, Wits, Vienna and North West Universities assessing the effects of differ different drug combinations that are commonly used to immobilize white rhinoceros. EEG:The team uses the Masimo Root with Sedline® EEG (electroencephalography) system to continuously monitor brain activity in the immobilised rhino. The sensors are placed on the frontal part of the rhino’s skull, and alcohol and gel are used to improve the contact between the skin and the sensors, which are secured to the rhino’s head with tape. The monitor displays EEG tracings that represent the electrical activity on both sides of the brain simultaneously and processes EEG indices that give an indication on the rhino’s level of anaesthetic depth.