This section is from the book "Dental Medicine. A Manual Of Dental Materia Medica And Therapeutics", by Ferdinand J. S. Gorgas. Also available from Amazon: Dental Medicine.
Ethyl chloride is best prepared by saturating an artificially cooled alcoholic solution of zinc chloride with hydrochloric acid gas; it may also be obtained as a by-product in the manufacture of chloral. It belongs to the ether class, and at ordinary temperature is a gas; but it is easily compressed, and then forms a colorless liquid possessing an agreeable, but not very strong ethereal odor, boiling between 500 and 53.6° F., and burning with a green flame. It is sold in the compressed state in hermetically sealed glass tubes, elongated to a capillary point, which serves not merely as a vehicle for containing it, but also as the apparatus for applying it, for owing to its low boiling point it is admirably adapted in this form to the rapid production of anaesthesia. The best manner suggested for breaking the flask or tube is to hold it vertically, attenuated end up ; grasp the pointed end with a pair of plyers and fracture at the file mark which is made nearer or at the end of the capillary elongation, so that the escaping stream of vapor shall be attenuated to the greatest degree possible, and then directed upon the surface to be anaesthetized. It is inflammable.
The. distance at which the glass tube should be held from the part to be anaesthetized varies considerably, for it may be two, six, eight, ten, or even twenty inches, depending somewhat upon the size of the aperture in the elongated end of the tube; it is necessary that the stream of vapor should reach the tissue exactly at the time of perfect volatilization. After the attenuated end of the tube is broken off at the file mark the tube is then everted, and the heat of the hand grasping it will accelerate the escape of the stream of vapor, which may be arrested by returning the tube to the position in which it was held when broken, and placing a finger over the aperture. Each flask or tube contains ten grammes of pure chloride of ethyl, which is considered to be sufficient for the extraction of about four teeth. When only a portion of the contents of the tube has been used, the remainder can be preserved by forcing the broken end into a rubber stopper and setting it in a cool place; or a little adhesive wax may be forced into the aperture, but not melted and dropped on.
Chloride of ethyl is employed in minor and dental surgery as a local anaesthetic, and its application does not occasion any untoward accessory symptoms, and it has no influence on the brain, having in this respect a great advantage over methyl chloride whose application is followed by a weakness of memory usually lasting for more than twelve hours; ethyl chloride does not produce the extraordinary cold which may cause destruction of tissue as does methyl chloride. Chloride of ethyl will produce general anaesthesia if inhaled, and it is therefore necessary when applying it within the mouth to have the patient breathe only through the nose, as there is no evidence of its safety as a general anaesthetic. Properly applied, and not too long continued, there is no danger of freezing the part to the stage of devitalization with consequent sloughing. On account of its great inflammability it must be used at a safe distance from a flame - preferably under electric light when applying it at night. As it is extremely volatile it should be kept in a cool place; and this extreme volatility is a proof that its effect upon the human system is of correspondingly brief duration, as it acts not by virtue of any inherent anaesthetic properties, but on account of the intense cold produced by its extraordinary rapid volatilization. Its depressing effect upon the circulation when administered is too pronounced for it to be regarded as a safe general anaesthetic. As a local anaesthetic, however, it has practically no effect upon the human system, and any of the drug that is absorbed into the system is eliminated in the course of a few minutes. It has given satisfactory anaesthesia in operations for cellulitis of fingers, buboes, abscesses, sinuses, boils, carbuncles, in-growing nails, etc., all forms of neuralgic pain, rheumatic pain, hyperaesthenic and reflex conditions.
Chloride of ethyl is employed in dental practice as a local anaesthetic for the extraction of teeth, and has proven very satisfactory in such operations. The adjoining teeth should be protected by a fold of napkin, the gum dried about the tooth to be extracted, and then coated with glycerine, and the vapor directed on the gum and not upon the tooth until the former turns white, when the forceps are applied. It is also used for obtunding the pulp prior to extirpating it, and also for obtunding sensitive dentine, for which purposes the rubber dam should be adjusted large enough to cover the nose, and the cavity dried, as the drug has little or no affinity for water, and the vapor thoroughly introduced to the sensitive surface of the dentine or to the exposed surface of the pulp, when the excavation or removal can be painlessly performed. Dr. L. E. Custer recommends grinding off the point of the tube with a corundum or carborundum disk about one-fourth of an inch further toward the end, in order that the jet of vapor may be so attenuated by escaping from a smaller orifice that it will not flood the cavity before it volatilizes fast enough. Chloride of ethyl is also employed for the relief of neuralgia by directing the vapor along the track of the affected nerve; also for diagnosing peripheral from centric neuralgias by applying the vapor at the point of irritation - if the neuralgia results from peripheral irritation the pain will cease at once; and intermittent applications, continued for from twenty to thirty minutes, are often curative when the irritation is not due to exposure of the pulp. Chloride of ethyl may also be employed for opening alveolar abscesses, removing tumors of the mouth, and in other painful affections of the oral cavity. Prof. C. Redard suggests that in the extraction of teeth in the lower jaw the vapor or stream be directed externally against the cheek, over the inferior maxillary nerve; while in the extraction of teeth from the upper jaw it be directed in front of the ear at the exit of the trigerminal nerve. When applied to a part chloride of ethyl first causes a hyperemia, then pallor, and gradually the part assumes a parchment-like appearance. From one to two minutes is gradually required, and the anaesthesia lasts as long again. It has been suggested to occasionally combine the action of chloride of ethyl with that of cocaine.
Anestile is a mixture of ethyl and methyl chloride and acts in the same manner as chloride of ethyl. (See Coryl.)