General Anesthesia by Cooling

Abstract

It is often desirable to induce in animals a general anesthesia for operative purposes without the use of drugs. This is particularly true where, as in the study of chromatophores, the effectors are especially open to drug stimulation and may remain responsive to minute amounts of the reagent for relatively long periods of time. As an effective means to a drugless anesthesia cold is very convenient. Fishes, amphibians, and reptiles may be immersed in cracked ice and water or simply in cracked ice till they are thoroughly chilled, which occurs ordinarily in from 10 to 15 minutes. They will then remain quiescent either on an operating board or on a bed of cracked ice till an operation can be performed. From this treatment the animals recover quickly at room temperatures and are soon quite free from any after-effects of the cold. They may, therefore, be tested, if this step is desirable, almost at once, for they contain no residual reagent, the complete disappearance of which must be awaited before further work can be done.

For some time fresh-water and salt-water fishes have been treated successfully in the Harvard Laboratories by this method (Parker, 1 Abramowitz, 2 Osborn 3 ). Recently Abramowitz has employed it on a larger scale in that dogfishes as much as a meter in length have been immersed in a tub containing cracked ice and seawater and there stupefied preparatory to an operation. Frogs are of course easily anesthetized either in cracked ice or in ice and water (Parker and Scatterty 4 ), and lizards may be chilled with cracked ice (Parker 5 ). Thus far we have treated only cold-blooded vertebrates, but Parker 6 has applied the method to newly-born rats.