White rhinoceroses (Ceratotherium simum) anesthetized with
etorphine combinations develop severe pathophysiologic changes, including
hypoventilation,
hypoxemia and
metabolic acidosis. The aim of this study was to evaluate the addition of
butorphanol to the immobilizing mixture on the cardiopulmonary effects in free-ranging white rhinoceroses darted from the helicopter. In the control group (n=15), the rhinoceroses were anesthetized with
etorphine,
azaperone,
detomidine, and
hyaluronidase administered intramuscularly. In the treatment group (n=16), 10-20 mg of
butorphanol was added to the combination. Within 10 min of becoming immobile, vital parameters (heart rate, respiratory rate, and temperature) and blood gas analyses were taken, and measurements were repeated after 10 (treatment group) and 20 min (control group). Both groups showed respiratory and
metabolic acidosis,
hypoxemia, and
hypercapnia. In the control group, the arterial partial pressure of
oxygen was significantly higher and the alveolar-to-arterial
oxygen pressure gradients were significantly lower in all body positions compared with the
butorphanol group.
Oxygen hemoglobin saturation in the control group was higher than in the
butorphanol group only in the lateral position. Improvements in arterial
oxygen levels were observed in all animals when placed in sternal recumbency. There were no significant differences in the mean induction times between groups, but the distance the
butorphanol group ran was significantly less after darting than in the control group. By adding
butorphanol to the immobilizing mixture, no benefits in ventilation were seen; although, size differences make comparisons difficult. Running for a shorter distance during induction could be beneficial in the prevention of severe
acid-base imbalances and capture
myopathy.