Abstract

I started working with dolphins in the early 1960s. At that time, dolphin anesthesia was of interest more for research than for medical care.¹ For example, in the 1930s, Langworthy wanted to study brain physiology. He gave a dolphin ether through a cone held over the blowhole.² The patient died, but Langworthy made excellent anatomical studies of the brain. Lilly reported on further attempts to study the brain.³ In 1955, a group of brain scientists tried to anesthetize dolphins using intraperitoneal pentobarbital. After several animals died, these efforts were abandoned.

In 1964, at the urging of Dr. Lilly, Dr. Forrest Bird made a control unit for his Mark 9 respirator. The unit imitated natural dolphin breathing. The lungs were inflated rapidly, held inflated for a set time, and then rapidly deflated and inflated again. In Dr. John Lilly’s laboratory in Miami, Florida, Nagel et al. used the Bird unit to support respiration after giving methohexital (5 mg/kg) and thiopental sodium (13 mg/kg) intraperitoneally.⁴ After seven hours, the endotracheal tube was removed, and the dolphin could breathe again. However, after nine hours, the dolphin lost respiratory control and died.⁴ With dolphins held in rigid restraints, further experiments tested nitrous oxide at 50 or 70% in the inhaled air. At the higher percentage, the animal became insensitive to noxious stimuli.⁴ After these results were published, I visited Dr. Nagel and colleagues to learn from their experiences. I decided to use the same Bird equipment but without rigid restraints. After my tests with nitrous oxide did not show deep anesthesia, I employed the more potent and widely used inhalation anesthetic halothane.⁵

In 1966, the Miami group described experiments with nitrous oxide in combination with the paralytic agent succinylcholine.⁶ In the summer of 1966, James McCormick, a graduate student of Professor E. G. Wever at Princeton University, came to work in my laboratory. He had interned in the Miami laboratory in 1964 and observed some dolphin procedures. We initiated further tests of nitrous oxide without rigid restraints and without succinylcholine. We found nitrous oxide inadequate and perfected our methods with halothane. These methods were used in both experimental and clinical cases.^7-10

From the 1930s until today, progress in dolphin anesthesia and surgery has been slow. However, each procedure has provided a step forward. The original Bird ventilator was used in many scientific and clinical procedures.^1,8-10 However, limitations were revealed over the years. Now there is need for an improved ventilator and procedures to make dolphin anesthesia a more routine clinical procedure.

Acknowledgements

I thank my early collaborator, Dr. James McCormick, and more recent collaborators, Drs James Bailey and Carolina Le-Bert.

Literature Cited

1.  McCormick JG, Ridgway SH. 2018. History of the development of anesthesia for the dolphin, a quest to study a brain as large as man’s. Anesthesiology. 129:11–21.

2.  Langworthy OR. 1932. A description of the central nervous system of the porpoise (Tursiops truncatus). J Comp Neurol. 54:437–499.

3.  Lilly JC. 1961. Man and Dolphin. New York, Doubleday, pp. 48–61.

4.  Nagel EL, Morgane PJ, McFarland WL. 1964. Anesthesia for the bottlenosed dolphin. Science. 146:1591–1593.

5.  Ridgway SH. 1965. Medical care of marine mammals. J Am Vet Med Assoc. 147:1077–1085.

6.  Nagel EL, Morgane PJ, McFarland WL. 1966. Anesthesia for the bottlenosed dolphin and author’s addendum. Vet Med Small Anim Clin. 61:233.

7.  Ridgway SH, McCormick JG. 1967. Anesthetization of porpoises for major surgery. Science. 158:510–512.

8.  Ridgway SH, McCormick JG. 1971. Anesthesia of the porpoise. In: Soma LR, editor. Textbook of Veterinary Anesthesia. Baltimore, Williams & Wilkins, p. 394–403.

9.  Ridgway SH. 1972. Homeostasis in the aquatic environments. In: Ridgway SH, editor. Mammals of the Sea: Biology and Medicine. Charles C. Thomas, Springfield, IL. p. 590–747.

10.  Ridgway SH. 2002. Asymmetry and symmetry in brain waves from dolphin left and right hemispheres: some observations after anesthesia, during quiescent hanging behavior, and during visual obstruction. Brain, Behav Evol. 60:265–274.