Physiological and behavioural effects of hypoxemia in reindeer (Rangifer tarandus) immobilised with xylazine-etorphine

This study examined the physiological effects of xylazine-etorphine (XE) immobilisation in reindeer (Rangifer tarandus), as well as post-immobilisation recovery and behaviour. Six reindeer weighing 105 +/- 18 kg (mean +/- s.d.) were immobilised via remote delivery of XE into the hind limb musculature. The animals were immobilised for 30 min on two separate occasions, and a randomised crossover design was used to assign nasal oxygen (O-2) or unsupplemented air to each animal. Arterial blood gases were collected and analysed at zero (time of arterial catheter placement), 5, 10, 20 and 30 min. Heart rate and respiratory rate, temperature, and arterial blood pressure were monitored every 5 min. After 30 min, immobilisation was reversed with naltrexone hydrochloride and tolazoline hydrochloride. The animals underwent behavioural testing (time required to navigate a novel maze) to assess cognitive function pre- and post-immobilisation. Significantly higher arterial O-2 tension levels were seen in O-2-supplemented animals (range 95-313 mmHg) compared with unsupplemented animals (range 26-70 mmHg). Hypoxemic animals had elevated heart rates and lactate levels compared with normoxemic. Immobilisation had a significant effect on the animals' ability to navigate a novel maze.