Although still applied infrequently, sedation of managed populations, and even free-ranging cetaceans has become an acceptable risk. On the other hand, anesthesia of managed cetaceans is still considered high risk to most zoo and wildlife veterinarians. Historical failures and limited experience have lead to myths and misconceptions about anesthesia of cetaceans. As well, the high value and relative difficulty with invasive support and monitoring has lead to hesitation in performance of medically necessary invasive procedures, leading to negative outcomes, further perpetuating the these misconceptions.
Managed populations include many killer whale (Orcinus orca), Beluga whale (Delphinapterus leucas), Pacific white-sided dolphin (Lagenorhynchus obliquidens), false killer whale (Pseudorca crassidens) and others. Still, most experience has come from work with bottlenose dolphin (Tursiops truncatus). Despite clear differences in body mass, common concerns include endotracheal intubation and extubation, body positioning and padding, body temperature management, vascular access and anesthetic agent.
Combinations of benzodiazepines (diazepam, midazolam), opioids (butorphanol, meperidine) have been used for pre-anesthetic sedation. Injectable anesthetic agents such as thiobarbaturates and propofol have been used for rapid sequence induction allowing manual orotracheal intubation by rostral luxation of the modified larynx. Inhalation anesthetics (halothane, isoflurane, sevoflurane) have been used reliably for maintenance of anesthesia. Ventilation by “apneustic plateau” and conventional methods have been applied with variable success and implore review. Anesthetic monitoring and vascular access are complicated by anatomic differences from terrestrial species. Imaging techniques and advanced non-invasive monitoring methods will advance the care of these species under general anesthesia.
The author thanks Dr. Chris Dold, Dr. Eric Jensen, and Dr. Sam Ridgway for their assistance and support of numerous cetacean projects and procedures in the aquatic animal medicine.