CHAPTER XV.
SEQUENCES.
By a sequence we mean a method in which anæsthesia is partially or wholly induced by one anæsthetic or one method, and maintained by another. The methods mentioned in Chapter XIII. as devised by Dr Guy for dental purposes are examples which have already been sufficiently described.
C.E. Mixture—Ether Sequence.
Of the method of inducing anæsthesia by C.E., and turning later to open-ether, we have also already spoken. One thing remains to be said in this connection. Learn to judge the appearance of the type of patient who will require this alternative to open-ether induction, and use the sequence to such patients from the beginning. Don’t start off with open-ether, and find out in a few minutes that the patient is too obstreperous. A change from mixture to ether is harmless, the reverse process needs much care.
The sequence of C.E. to closed ether was advocated by Hewitt as a means of dealing with very alcoholic men, and for this purpose has great merits. The mixture is given until the stage of struggling is just about to commence, a point which experience enables one to fix with considerable accuracy. The remainder of the induction is conducted by a closed-ether inhaler, either the Hewitt wide-bore or preferably the Ormsby. The ether indicator which stands at about one when the inhaler is first applied, may be advanced very rapidly full ether strength being attained within a minute or two. As soon as rebreathing is begun with either of these instruments, it is very striking to watch the rapid and apparently safe subsidence into anæsthesia of the most troublesome patient. The struggling is cut short and greatly minimised in violence, and a stage which under CHCl3 might have presented some considerable risk of secondary syncope, is thus eliminated.
Nitrous Oxide and Ether Sequences.
This is a method greatly superior to the induction by closed-ether described on p. 79. Instead of the 1-gallon bag of the Clover or Hewitt instrument, the valve piece and 2-gallon bag of a gas apparatus are attached to the head of the ether inhaler (Fig. 23, on page 77).
Once the gas bag is inflated from the cylinder, the supply of gas may be cut off. A few breaths of gas “upon the valves” are given, until the bag is half empty; the valve tap is then pushed over to “no valves” and rebreathing begun. Ether may be turned on a few seconds later, and the strength of the vapour may be increased more rapidly. Three-quarter strength of ether may be attained as a rule in ninety seconds. There is very little likelihood of struggling in this method.
Ethyl Chloride and Ether.
This is a valuable method for short operations, being easily portable, speedy and safe in action, and fairly agreeable to the patient. Some anæsthetists use this induction method as a prelude to open-ether.
The Clover (or Hewitt wide-bore) instrument is interposed between the face-piece and the T. of the ethyl chloride inhaler, as shown in Fig. 47. A small dose of ethyl chloride only is requisite; for an adult, 3 c.c. is enough. This is vapourised over hot water in the usual way; a very light anæsthesia is induced in some sixty seconds, and the ether can then be turned on at a much quicker rate than if the induction be conducted by that drug alone.
Fig. 47.—Clover’s Inhaler adapted for the Ethyl Chloride-Ether sequence.
Scope.
The gas-ether and ethyl chloride-ether sequences are most useful methods. They are quick, safe, and powerful.
Either may be used as “single dose” anæsthetic, the ether being pushed quickly up to “full” and the inhaler then withdrawn. If, however, no access to the mouth is required by the surgeon, ether anæsthesia may, by occasional breaths of fresh air be prolonged for as long as desired.