A safe and effective technique for underwater anesthesia of green sea turtles (Chelonia mydas) was developed to allow fully submerged in-water measurements of auditory evoked potentials (AEP) without myogenic artifact. Turtles were anesthetized using medetomidine 50 µg/kg and ketamine 5 mg/kg IV, and ventilated via a custom-designed double-cuffed extended endotracheal tube while submerged to an ear depth of 10 cm for up to 60 min. Procedures conducted on manually restrained turtles, submerged within range of the water surface so they could breathe voluntarily, were compared with those conducted using anesthesia, based on blood gas measurements and the ability to record AEPs. Quality AEPs were recorded from both anesthetized turtles and four of seven manually restrained turtles, while AEP recordings were impossible for the remaining manually restrained turtles due to myogenic artifact. Manual restraint was superior to anesthesia for turtles that did not resist restraint (better venous blood oxygenation, acceptable AEPs), but anesthesia was superior to manual restraint when compared with turtles that did resist (marked lactic acidosis, and AEPs not possible). Underwater anesthesia of sea turtles is a viable option for specialized physiologic testing requiring submerged inactive subjects.
We thank W. Horne and N. Abou-Madi of Cornell University for discussions on anesthesia strategy, D. Michels and J. Steigleiter of MILA International, Inc., for fabricating the double-cuff extended endotracheal tubes, and C. Harvey-Clark and B. Bostrom of the University of British Columbia for assistance during the procedures. Funding was provided by the National Marine Fisheries Service and the Wider Caribbean Sea Turtle Network (WIDECAST).