Physiologic Effects of Nasal Oxygen or Medical Air Administered Prior to and During Carfentanil– Xylazine Anesthesia in North American Elk (Cervus canadensis manitobensis)

This study compared the physiologic effects of carfentanil–xylazine anesthesia in elk administered nasal oxygen or medical air. Eight female 5 ± 2-yr-old (mean ± SD) captive elk (Cervus canadensis manitobensis) weighing 245 ± 20 kg and habituated to chute restraint were studied in a randomized crossover. Nasal insufflation of oxygen or medical air (10 L/min) was provided prior to and throughout anesthesia. Baseline data were collected before i.m. injection of carfentanil (10 μg/kg) and xylazine (0.2 mg/kg). Arterial blood gases (PaO2 and PaCO2), arterial blood pressure, heart and respiratory rate, and observations of muscle rigidity and movement were collected every 3 min for 30 min. Drugs were antagonized at 30 min with i.m. naltrexone (1 mg/kg) and tolazoline (2 mg/kg). Induction and recovery were significantly faster (mean ± SD) in elk receiving oxygen (208 ± 39 and 333 ± 63 sec, respectively), vs. medical air (306 ± 84 and 532 ± 201 sec). Elk receiving oxygen had a significantly higher PaO2 and PaCO2, and significantly lower pH and heart rate. Minimum PaO2 was 75 ± 30 mm Hg (oxygen), and 28 ± 6 mm Hg (air). Maximum PaCO2 was 89 ± 5 mm Hg (oxygen), and 64 ± 4 mm Hg (air). Frequency of rigidity and movement decreased when PaO2 ≥ 70 mm Hg. Animals breathing air demonstrated slower inductions and recoveries, severe hypoxemia, and increased rigidity and movement. Oxygen administration reduced hypoxemia and improved anesthesia quality, but caused prolonged periods of apnea, and moderate to severe hypercarbia and respiratory acidosis.