Handbook of anæsthetics

Chemically this drug has the formula C₂H₅Cl. It is a colourless fluid so volatile that it boils at ordinary room temperature. Its vapour is highly explosive, and the fluid itself very inflammable. The drug is supplied by the makers in small tubes with a metal end which can be opened by pressing a little lever (see Fig. 40), varying in type with the brands made by various makers. Two brands are sold by each firm; one is chemically pure, intended for use as a general anæsthetic; the other is not so pure, and is only sold for local anæsthesia. Such a product is not suitable for inhalation.

Physiology.

The special points in the physiology of ethyl chloride may be briefly summarised as follows:—

In the majority of cases, death appears to take place from paralysis of the respiratory centre, the heart still showing a little power of contraction after respiration has ceased. There is therefore a fair prospect of recovery if artificial respiration be resorted to promptly.

Methods of Administration.

Open Method.

The extreme volatility of the drug has discouraged most anæsthetists from giving it upon an open mask. Hornabrook, of Melbourne, advocates this system, however. His mask fits the face accurately, and his whole method is strictly perhalational. He uses some 4–6 c.c. of the drug for a child, 6–8 c.c. for an adult, and achieves his anæsthesia in a minute to a minute and a half. He also advocates open ethyl chloride as a preliminary to open ether. For some twelve months, the author adopted the method. At the end of that time he came to the conclusion that while it greatly facilitated the induction stage of open ether, it appeared to increase the after sickness. He therefore abandoned it, though rather reluctantly.

Closed Method.

This is the usual means employed. A variety of inhalers have been produced on the market, one of which is shown in Fig. 41. Essentially all consist of:—

Administration.

To use such an inhaler, the glass vial is first detached from the rubber tube, and the chosen dose of drug squirted into it. A child of five or six will require 3 c.c., an adult up to 5 c.c.; this dose should never be exceeded. The vial is then rapidly reconnected with the inhaler. The face-piece is adapted to the face, care being first taken to place between the teeth a mouth prop or a gag. This enables one to get immediate access to the mouth when the inhaler is removed. The patient is then told to breathe deeply once or twice. During the inspiration the mask is lifted slightly, and the ensuing expiration is then caught in the bag by pressing down the mask on to the face. To volatilise the drug there are two alternative methods. In the one, part or the whole of the dose is tipped into the rubber bag by elevating the vial. A far better is the “Vapour” method, almost universally used in Edinburgh owing to the advocacy of Dr Logan Turner. A tumbler is filled with hot water, and the bottom of the glass vial is allowed first to touch, and after a few seconds to be immersed in it. Some thirty to forty seconds suffice to vapourise the whole of the dose.

Ethyl chloride given by itself should always be administered to a patient in the recumbent position. A dose sufficient to produce anæsthesia without the aid of nitrous oxide or ether will not be safe in the erect posture. The case is quite different where a small dose only is given, to assist the action of nitrous oxide, or facilitate the induction stage of ether.

Signs of Anæsthesia.

Ethyl chloride is very rapid in its action, some sixty seconds availing to produce quite a deep anæsthesia. Respiration is at first deepened and quickened: as full anæsthesia is attained it remains rather deeper than normal, and is accompanied usually by light snoring. The colour should remain perfectly good: the pupils show marked dilatation, the corneal reflex is abolished, and good muscular relaxation is attained.

With no anæsthetic is it so essential as with this, to become acquainted with the type of respiration normally to be expected, and to watch for any departure therefrom with cat-like vigilance. The other danger signal is the pupil. It should be dilated, but a rim of iris should still be perceptible.

Once anæsthesia is established, the inhaler should be removed, and the surgeon may begin his work. He will have for its completion some 80–90 seconds against the 40–50 available after nitrous oxide. With ethyl chloride there is a somewhat prolonged “analgesic” stage. The patient is partly conscious and may even be phonating, but seems unconscious of the infliction of pain unless very severe measures are being used.

The Scope of Ethyl Chloride.

When first introduced, it was expected by enthusiasts that the lightness and portability of the drug itself and of the necessary inhaler, would enable ethyl chloride to oust nitrous oxide from its recognised place in surgery and dentistry. These high expectations have for several reasons not been fulfilled. In the first place, this drug is essentially a “single dose” anæsthetic. Most authorities view coldly all attempts to prolong anæsthesia by repeated or continued administration. Secondly, ethyl chloride has a mortality rate very much greater than nitrous oxide if doses sufficient in themselves to produce anæsthesia are habitually used (vide supra). The introduction of the “vapour” method has done much to mitigate the risks, but even then, this anæsthetic cannot approach the high level of safety rightly credited to N₂O. Moreover, it leads to after vomiting much more commonly than its rival.

In many schools these considerations have been held so powerful that ethyl chloride has been entirely abandoned. It is, however, a very valuable drug for the following purposes:—