Among the other cocaine substitutes in general use are betaeucaine, tropacocain, anesthesin, and subcutin.
These all find a special field of usefulness, but for general work, are limited, because of some disadvantages which each and all of them possess.
Individual selection plays an important part in the use of a local anesthetic, and one operator, by practical experience, may obtain results with a given drug, which another fails to achieve.
The essential feature to be remembered by the practising chiropodist is, that the use of any drug employed for anesthetizing purposes, even though but local, should be safeguarded in every way.
Cold. The methods of using ether, rhigolene, or ice and salt, to produce cold, are slow and unsatisfactory. If cold is to be used to produce local anesthesia the most efficient and convenient method of applying it is by means of ethyl chloride. This fluid is very volatile and is best controlled by having it in air-tight tubes. When not in use, a valve covering one end of the tube prevents leakage. When the valve is pressed upon, the orifice of the tube is opened and the heat of the hand forces out a fine stream of the liquid which is directed upon the parts to be frozen. Rapid evaporation causes intense cold. The nozzle should be held about fifteen inches from the area to be acted upon. When the spray strikes the integument, redness almost instantly results but in a few seconds the part becomes hard and white. This condition indicates local insensibility and lasts about two minutes. If the action is slow, it can be much hastened by gently blowing upon the parts to increase the rapidity of evaporation.
The refrigeration method of local anesthesia is of limited usefulness and is recommended only for the opening of felons and abscesses, for removing wens from the scalp and back, and for producing a painless area in which a puncture is to be made. It must be borne in mind that sloughing and ulceration of the skin are liable to follow the use of cold.
Work under this form of anesthesia must be done with rapidity not always consistent with thoroughness, and should therefore be employed only when a single incision or puncture is indicated.
The pain incident to subsequent thawing is severe and, in general, is about as hard to bear as an incision without an anesthetic.
For the purposes of practical podiatry, the chiropodist is advised to use a substitute for cocaine rather than the cocaine itself when local anesthesia is necessary. In the clinics of the School of Chiropody of New York, novocaine, quinine and urea hydrochloride, and alypin are preferred, and no single instance of toxemia has ever been experienced. There have been cases in which the anesthesia did not prove thoroughly effective, but, in the main, these drugs have well answered the purposes of their use.