Semidomesticated Eurasian tundra reindeer (Rangifer tarandus tarandus, n = 21) were scheduled twice for chemical immobilization with medetomidine–ketamine as part of a scientific experiment in June 2014. During the first round of immobilizations, seven animals developed severe respiratory depression (RD). Three individuals died, and 4 recovered. The ambient temperature during the 2 days of immobilization (June 3 and 4) was high (mean 13.9–17.6°C) compared to the normal mean temperature for these 2 days (7–8°C) based on statistical records. During the second round of immobilizations, using the same anesthetic protocol for the remaining animals as in the first round but conducted under cooler conditions (mean 6.6°C for the period June 9–18), no signs of RD were observed. Clinical and pathological investigations indicated that the animals suffered from circulatory changes possibly caused by high ambient temperatures and granulomatous interstitial pneumonia due to Elaphostrongylus rangiferi larvae. These conditions, together with the cardiovascular effects of medetomidine, were likely causes of RD and the fatal outcome. We conclude that chemical immobilization of reindeer with medetomidine–ketamine should be avoided in May–June due to the potential risk when animals partly in winter coats encounter rising ambient temperatures and usually have parasites developing in their airways.

半驯化的欧亚苔原驯鹿（塔兰吉斯犬（Rangifer tarandus）2014年6月，作为科学实验的一部分，有21次被安排使用美托咪定-氯胺酮化学固定两次。在第一轮固定期间，七只动物出现了严重的呼吸抑制（RD）。三人死亡，四人康复。根据统计记录，在固定的2天（6月3日和4日）中，环境温度比这2天的正常平均温度（7-8°C）高（平均13.9-17.6°C）。在第二轮固定期间，对其余动物使用与第一轮相同的麻醉方案，但在较凉的条件下（6月9日至18日的平均温度为6.6℃）进行麻醉，未观察到RD的迹象。毛圆线虫幼虫。这些情况以及美托咪定的心血管作用可能是引起RD和致命结果的原因。我们得出的结论是，在5月至6月应避免使用美托咪定-氯胺酮化学固定驯鹿，因为部分穿冬大衣的动物会遇到环境温度升高，并且通常在气道中生长出寄生虫的潜在风险。