During anesthesia of wild animals, hypoxemia is often not treated, or not even recognized, even though hypoxemia can result in morbidity and mortality. Both free-ranging and captive brown bears (Ursus arctos) anesthetized with medetomidine-zolazepam-tiletamine (MZT) commonly develop mild to marked hypoxemia.1 The aim of this study was to determine the minimum effective flow-rate of intranasal oxygen for prevention or treatment of hypoxemia in anesthetized brown bears. The study included 26 free-ranging brown bears (yearlings, subadults, and adults; body mass 12–250 kg) in Sweden, which were darted with MZT from a helicopter. During anesthesia, oxygen was administered via a nasal line inserted 2–5 cm into the nasal cavity. Arterial blood samples were collected before and during oxygen therapy and immediately processed with an i-STAT® Analyzer (Abbott Laboratories, Abbott Park, IL). Rectal temperature, respiratory rate, heart rate, and pulse oximetry-derived hemoglobin oxygen saturation were recorded. Intranasal oxygen supplementation at a flow rate of 0.5–3.0 L/min increased the partial pressure of arterial oxygen >100 mm Hg. In relation to the body mass of the bears, the following flow rates were adequate: 0.5 L/minute to bears up to 25 kg, 1 L/minute to bears up to 36 kg, 2 L/minute to bears up to 184 kg, and 3 L/minute to bears up to 250 kg. In conclusion, low flow rates of intranasal oxygen were sufficient to improve arterial oxygenation in anesthetized brown bears.
We thank the Scandinavian Brown Bear Research Project and the field supervisor Sven Brunberg, for invaluable collaboration. Also, thanks to Ulf Grinde and Åke Pettersson, pilots at Jämtlands Flyg.
1. Fahlman Å. Advances in Wildlife Immobilisation and Anaesthesia: Clinical and Physiological Evaluation in Selected Species [PhD thesis]. Uppsala, Sweden: Swedish University of Agricultural Sciences; 2008.