Evaluating the Efficacy and Safety of Guaifenesin as an Injectable Anesthetic Agent in Elasmobranchs
Abstract
Performing anesthetic procedures in elasmobranchs can offer a variety of challenges based on the mode of administration, environmental factors, individual animal metabolism, and lack of approved drug protocols.2,5 Many accepted techniques are extrapolated from mammalian species and often differ in expected efficacy and duration.6
Guaifenesin, a muscle relaxant with an unknown mechanism of action, has widely been used in anesthetic protocols of terrestrial species1,3,4 but its use has not yet been documented for aquatic animals. It is the goal of this case series to determine the practicality of a guaifenesin bolus as an anesthetic agent in elasmobranchs.
Five southern stingrays (Dasyatis americana) and one bowmouth guitarfish (Rhina ancylostoma) were anesthetized with 50–75 ppm MS-222, moved into fresh saltwater, and then received a bolus of guaifenesin intravenously at varying doses between 10–40.5 mg/kg. Heart rate in all animals was monitored continuously via ultrasound during and immediately following guaifenesin administration; all five stingrays experienced brief episodes of asystole during injection which spontaneously resolved with no lasting ill-effects. Other cardiopulmonary effects observed in association with guaifenesin administration were bradycardia and tachypnea.
Although a surgical plane of anesthesia was not obtained with intravenous guaifenesin, heavy sedation with muscle relaxation was achieved for short term procedures. Further studies are required to determine safe dosing ranges and to explore protocols for guaifenesin use as a continuous rate infusion.
Acknowledgments
A debt of gratitude is owed to the aquarium and hospital staff at Disney’s The Seas with Nemo and Friends® at Epcot®, Disney’s Animal Health Department, as well as the Animal Health Department at the John G. Shedd Aquarium.
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