Effects of Some Basal Anesthetics on Vasomotor Reflexes

Abstract

In a study of the relative efficiency of basal anesthetics it was frequently noticed that in animals under varying doses of barbiturates (amytal, allonal and dial) the blood pressure showed a depressor response upon stimulation of the central end of the divided sciatic nerve. As such reversal of normal reflexes has been noted with other drugs such as chloroform, it seemed worth while to investigate the effect produced on vasomotor responses by these barbiturates and those produced by some other basal anesthetics or hypnotics. Cats were used, and satisfactory experiments were conducted with the different basal anesthetics in the following numbers (amytal 4, dial 6, and allonal 5). Under the influence of novocain, a tracheal cannula was inserted in order to administer ethylene 90% oxygen 10% for anesthesia to complete the preparation, that is to cut the sciatic and insert a carotid cannula to record the blood pressure. The central end of the sciatic was stimulated with a Dubois Raymond coil connected with 3 dry cell batteries in parallel to give a voltage of 6. As the response of different cats to the same strength of stimulus varies so greatly no average figures for the stimulation used can be given. The minimal strength required to produce a vasomotor response after 20% of the M.L.D. of these drugs was stimulation with the secondary coil at 20 cm. in some cats, while in others no response would be obtained until the secondary coil was at positions intermediate between this and 11 cm. The barbiturates were given intraperitoneally. The usual procedure was to give 20% of M.L.D. while the cats were still under the ethylene, and after a fixed interval (10 minutes was sufficient for the full effect to be produced) the ethylene was discontinued and 5 minutes allowed for its effect to be lost.