Spinal Anesthesia in Winter Frogs. ∗

Abstract

In a previous communication 1 a simple method for producing spinal anesthesia in the frog was described. In addition, a series of 10 local anesthetics were studied in summer frogs, kept at temperatures of from 26° to 29°C. The data obtained on each drug included the determination of the minimal anesthetic dose, minimal lethal dose, duration of anesthesia produced by a sublethal dose, and the calculation of a therapeutic coefficient from the fraction M.L.D./M.A.D. Comparatively, this coefficient gives evidence of the usable therapeutic range for each local anesthetic.

In this paper similar results are described in which 7 local anesthetics were injected intraspinally into winter frogs kept before, during and after the experiments at 10° to 12°C. This series includes those local anesthetics showing, experimentally, the best possibilities for use in human spinal anesthesia. Five of these drugs had been studied previously in summer frogs, but because of the relatively high temperature prevailing at that time, it was thought advisable to repeat the work at a lower temperature and perhaps a more satisfactory one for frogs. Because of great variations noted in frogs, which are ascribed to seasonal and temperature changes, a further check on uniformity was attempted by carrying out the complete series during two winters. Consequently the first series was carried out between October 10, 1931, and February 20, 1932, and the second, between the same periods of 1932–33. As can be seen from the table no great variations are to be observed between the 2 series. It might also be added that the results obtained on winter frogs show a close parallel to similar data obtained on the rabbit, These will be reported later.