Abstract

At the Alaska SeaLife Center, Steller sea lions (Eumetopias jubatus) are routinely anesthetized to facilitate research and veterinary procedures. Between 1998 and 2011, two adult female Steller sea lions underwent a total of 185 anesthetic procedures. The procedures ranged from 6 to 277 minutes. No pre-medications were given and general anesthesia was induced and maintained using isoflurane gas in medical oxygen. Vital signs were recorded using manual and electronic monitoring. During this period, there were 14 episodes of pronounced or prolonged bradycardia that were managed by decreasing the concentration of isoflurane and/or by administering intramuscular (IM) or intravenous (IV) atropine. Minimum heart rates ranged from 43 beats per minute (bpm) to 53 bpm. Following a decrease of isoflurane concentration (2 cases), the heart rate slowly increased, requiring 42.5 ± 3.5 minutes to rise into a normal range (above 60 bpm). Heart rate rose more quickly following atropine administration, taking 9.3 ± 4.2 minutes when given IM (10 cases) and 1.5 ± 0.7 minutes when given IV (2 cases) to increase above 60 bpm. In the cases where no atropine was given, five minutes after the minimum heart rate was recorded the heart rate was 48.0 ± 0.0 bpm, a change of 1.5 ± 2.1 bpm from the minimum heart rate. In the cases where atropine was given, at five minutes post-atropine the heart rate was 52.1 ± 10.9 bpm for IM atropine and 79.5 ± 9.2 bpm for IV atropine, with changes of 7.6 ± 8.1 bpm and 30.5 ± 2.5 bpm from the minimum heart rates, respectively. By 15 minutes, the heart rates were 50.5 ± 0.7 for no atropine, 71.8 ± 6.8 for IM atropine, and 82.5 ± 10.6 for IV atropine. The changes from the minimum heart rate at 15 minutes were 4.0 ± 1.4 bpm for no atropine, 25.8 ± 9.2 for IM atropine, and 33.5 ± 4.9 for IV atropine. The use of atropine is recommended to treat isoflurane anesthesia-induced bradycardia in Steller sea lions. In addition, using atropine prophylactically may help avoid bradycardia during isoflurane anesthesia.

Acknowledgements

The authors thank the Husbandry, Veterinary, and Research staff members at the Alaska SeaLife Center who provided care for and assisted with the anesthesias of Sugar and Kiska, the Steller sea lions in this report. These animals have been held under NOAA Permit 14334. The anesthetic procedures required to perform research and the research protocols were reviewed by the Alaska SeaLife Center IACUC (AUP 09-003).