Abstract

The development of sedation and anesthesia techniques has lagged behind other species for a variety of reasons. Popular theory held that these species were voluntary breathers who would not continue to breathe with sedatives or anesthetic agents. As manatee cases presented to rehabilitation facilities increased so did the potential need for using these agents to provide basic care.

The first manatee at Sea World to require sedation received midazolam and meperidine in conjunction with lidocaine to remove a sequestrum from the radius of his right pectoral flipper. Midazolam has been used at 0.044 mg/kg to calm fractious individuals for therapeutic techniques such as debridement and enemas, and to transport excited animals. This provides a sedative effect for 60 to 90 minutes. Since manatees like cetaceans, are breath holders the clinician must check the animal for response to stimuli, respiratory rate and reflexes. When sedated manatees will close their eyes but should maintain palpebral reflexes and will open their eyes to high pitched noises which resemble calf vocalizations. After completion of a short clinical procedure if the animal requires tube feeding or will be placed back into water the midazolam is reversed with flumazenil.

General anesthesia with isoflurane was first utilized in 1990 in an attempt to perform gastroscopy on an adult female manatee. Initial attempts at intubation were unsuccessful when it was found that the small size and curvature of the oral cavity coupled with a long soft palate made visualization of the glottis extremely difficult. Examination of respiratory system of post mortem specimens revealed that the most direct access was through the nasal cavity. Preanesthetic sedation with midazolam at 0.077mg/kg allows intubation in approximately 50% of the individuals. If additional relaxation is required the manatee may be masked with isoflurane to facilitate intubation. The mask of choice is a modified 5 gallon plastic water container with the bottom removed to fit over the animals head. This allows for adequate oxygen and anesthetic inhalation without restricting intake. Individuals during induction may go for extended periods without breathing. If breathe intervals are prolonged and ineffective because of heavy sedation then hypoxia may compromise the animal. Intubation is achieved by placing an endoscope in one nasal cavity to visualize the glottis then inserting an elongated endotracheal tube in the other nasal opening which is guided into the glottis.

Monitoring of anesthesia should include pulse oximetry, in line carbon dioxide levels, or serial blood gases. Complications during recovery include hypercapnia and tube occlusion with mucous.

 a. Midazolam HCL, Hoffman-LaRoche Inc., Nutley, NJ

 b. Flumazenil, Hoffman-LaRoche Inc., Nutley, NJ