Cocaine.

—Of the local anesthetics cocaine, or some of its compounds or substitutes, will give the best results; although it is said that injections of pure water, if sufficiently bulky, will also answer the purpose of a local anesthetic. Cocaine has marvellous properties upon mucous surfaces or in the tissues, but none upon the unbroken skin. Where the parts to be operated are covered with skin it is necessary to inject the drug with a hypodermic syringe, as in the case of all deeper tissues. About the eye, the drug is used in from 1 to 4 per cent. strength; in the nasopharynx, from 2 to 4 for ordinary purposes; about the genitals, 2 to 5 per cent.; beneath the skin, ordinarily in strength of 1 to 2 per cent. In operations upon the nasopharynx and larynx it is often advisable to make a local application of a small amount of an almost saturated solution, by which a more complete effect is gained.

Cocaine is not without dangerous toxic properties, to which some persons are peculiarly susceptible. It will seriously disturb heart action in some; in others produce vertigo and mild delirium, and in still others peculiar erotic symptoms. Warm solutions are more quickly absorbed than cold ones. The use of more than 0.06 (1 grain) should be avoided.

When the skin alone is to be anesthetized the injection should be made into and not beneath. The nearer the cocaine solution is deposited to the principal nerve trunk or branches the more promising will be its effect.

The use of cocaine in operations, under general anesthesia, for the prevention of those depressing influences which cause lowered blood pressure and shock, has been alluded to in the chapter on Shock. For instance, it is well to spray the larynx after opening it and before making further operation upon it; while in all major operations in which large nerve trunks are exposed or divided, e. g., amputations, etc., the injection into the nerve trunks of a few drops of 2 or 3 per cent. cocaine solution prevents this kind of disturbance.

For small and localized operations the direct injection of cocaine into and around the area involved will prove sufficient. It is rarely necessary to use for this purpose a solution stronger than 1 or 2 per cent., especially if it is deposited drop by drop around the entire margin of the area and if the part have been previously made bloodless by pressure, as by the Esmarch rubber bandage. But when extensive operations are to be undertaken the method of “blocking,” so called, should be carried out. This consists in cocainizing the principal nerve trunks which supply the part, for which purpose an accurate knowledge of regional neural anatomy is necessary, with the intent to inject into or closely around the nerve trunks a few drops of a 1 or 2 per cent. solution. Working in this way by combination of injection, then of incision, by which the nerve trunks are better exposed and more fully protected in order to be more completely injected, and then proceeding farther with the operative part, extensive operations have been and may be done; such for instance as amputations, not alone of the limbs but even of the shoulder girdle, removal of large tumors, etc. In this way, for example, Kocher now removes most of the goitres which he attacks. The essential feature of this work is to first get the cocaine inside of the nerve sheaths. In this way a minimum of the drug is used with a maximum of effect. Nevertheless when a large nerve trunk is thus to be paralyzed temporarily it is best to inject the solution directly into it as well as around it inside the sheath. Cocaine is a temporary protoplasmic poison, and for the time being shuts off the afferent power of the nerve. One advantage of this method is the avoidance of shock as well as of pain. Another method, devised by Schleich, is to be preferred. He uses three different solutions, of which the second is commonly used. Tablets for making these solutions can now be obtained. In order to secure the best effect with them the parts should be made bloodless. The solution is deposited subcutaneously in a series of drops around the margin of the area, and then massage may be made to distribute the fluid more uniformly in the tissues. When the tissue to be operated upon is inflamed the injections should be made first into the healthy area on the proximal side.

Schleich’s formulas are as follows:

No. 1.
Cocainæ hydrochloridi.200(gr. iij).
Morphinæ hydrochloridi.025(gr. ²⁄₅).
Sodii chloridi.200(gr. iij).
Aquæ destillatæad 100.000(f ℥ iiiss).
No. 2.
Cocainæ hydrochloridi.100(gr. iss).
Morphinæ hydrochloridi.025(gr. ²⁄₅).
Sodii chloridi.200(gr. iij).
Aquæ destillatæad 100.000(f ℥ iiiss).
No. 3.
Cocainæ hydrochloridi.010(gr. ¹⁄₆).
Morphinæ hydrochloridi.005(gr. ²⁄₅).
Sodii chloridi.200(gr. iij).
Aquæ destillatæad 100.000(f ℥ iiiss).

Various substitutes for cocaine are now on the market. Some of these are soluble and some insoluble. Eucaine is most commonly used, especially in form known as eucaine B., or beta-eucaine. It is weaker than cocaine, especially so in toxic properties, and solutions of twice the strength can be used, often with satisfaction, and almost always without danger. For urethral and eye work, e. g., it answers the purpose; nevertheless, it will sometimes prove disappointing. Orthoform is a crystalline, sparingly soluble artificial product, which is too light and too coherent to be generally serviceable. It often gives satisfaction mixed with other powders or in ointments, and it is usually free from toxic properties. Nervanin is another laboratory product, not equal in activity to cocaine, but almost free from unpleasant properties. Anesthesin is another similar product, which is practically free from physiological properties save that it acts as a local anesthetic. The latter may be employed for infiltration anesthesia in the following proportion, recommended by Dunbar:

Anesthesin hydrochloride0.250
Sodium chloride0.150
Morphine hydrochloride0.005to 0.015
Water100.000Cc.