This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
As the anaesthesia deepens, the reflex and automatic excitability of the cord and medulla is also diminished, and the phenomena that ensue affect all the parts supplied by these centres. The muscular tone is lost, and the voluntary ran-become paralysed and relaxed. The pupil is semi-contracted, and may dilate on stimulation of afferent nerves. The heart and respiratory organs are no longer excited, but their centres in the medulla being now depressed, their action is laboured, the pulse falling in frequency (a striking change from the previous acceleration) and in strength, and the respiratory movements being slow, heavy, and attended by noise or stertor.
Now is the time for the surgeon to operate, anaesthesia being complete, whilst the depression of the vital functions is still within safe limits. The effects may be expected to pass off in a few minutes if the administration be stopped; and although the amount required to complete the second stage varies greatly with the subject and other circumstances, it may be said that from 1 to 4 fluid drachms will probably have been given up to this point. K - 8 c. Third stage. - Beyond the second stage or degree, chloroform anaesthesia is highly dangerous, the further action of the drug being attended by complete loss of all reflex excitability of the cord and medulla. The sphincters relax, the pupils are widely dilated and fixed, the globes prominent. The respiratory centre is no longer irritable, and the movements of the chest become weaker, irregular, sighing, and finally cease. The cardiac centre fails, the heart beating irregularly and feebly, and at last stopping in diastole, both from central and from direct nervo-muscular depression. The blood-vessels dilate, the pressure falls to zero, and the circulation has come to a standstill. It is obvious that the direct effects of chloroform on the respiratory centre are complicated towards the last by venosity of the blood. Death may occur through the heart, the respiration, or both together.
Analysis Of The Phenomena Of Chloroform Anaesthesia. Chloroform anaesthesia affords us an excellent opportunity of studying the action of a drug upon the various centres of the nervous system, from the highest downwards. The first parts to be stimulated are the cerebral centres with mental functions, the control of the special senses and consciousness; and these are the first to be depressed and finally annulled. The lower cerebral and spinal centres are affected less and somewhat later, so that a certain degree of excitement of these accompanies the first cerebral depression; and the spinal centres being no longer controlled by the cerebral, irregular excessive movements of the limbs ensue. As the depression deepens in the spinal centres, the muscles are paralysed. Lastly, the lowest centres of all, those of organic life, connected with the heart, vessels, respiratory organs, and sphincters, situated in the medulla and cord, yield to the action of chloroform. Although affected from the first, it is not until the higher parts have become completely overpowered that the functions of these vital centres are seriously impaired, and death threatens. It is on account of the safe order of invasion of the different centres by chloroform that it has been selected as the proper agent for temporarily arresting consciousness; we shall find that many other powerful drugs equally depress the nervous system, but in a direction exactly the reverse.
The peripheral nerves are affected last of all in general anaesthesia, and it must be repeated that the loss of sensibility to the knife is due to a central, not a peripheral effect.
The muscles are finally affected directly, as well as through the nervous system. The pupil is dilated in the first stage, probably by stimulation of the sympathetic; and contracted in the second, and dilated in the third stage, by stimulation and paralysis respectively of the third nerve or its cerebral centre. The other involuntary muscles are less obviously paralysed, and the parturient uterus contracts freely in complete anaesthesia, with some loss, however, of vigour and regularity.
Specific Uses Of Chloroform. The circumstances under which chloroform anaesthesia may be employed are the following: (1) In operations attended by pain. These need not be particularised. (2) In operations where muscular action or spasm has to be overcome: reduction of hernias, dislocations and fractures; catheterism. (3) In diagnostic manipulations: exploration of the abdomen externally and per rectum. (4) In diseases attended by excessive pain, especially biliary and renal calculus. (5) In parturition, in certain subjects and conditions, the degree of anaesthesia induced being generally slight until the moment of birth. (6) In spasmodic diseases, such as tetanus, hydrophobia, uraemia, puerperal convulsions, the status epi-lepticus, severe chorea, and hiccup.
Method Of Administration, And Principal Precautions To Be Observed In Chloroform Anaesthesia. This is a purely practical subject, to be learned by experience and not in theory. The student has frequent opportunities of witnessing the administration of anaesthetics by skilled persons, and he must closely and carefully observe every effect of the chloroform upon the patient. He will do well to interpret every phenomenon as it arises, such as mental and muscular excitement, the character of the breathing, the colour of the countenance, and (if possible) the state of the pulse, into exact physiological terms, as explained above; as, for example, stimulation of the convolutions and cord, interference with the respiratory centre, etc. He will thus come to appreciate accurately the condition of the patient at any moment, and be prepared to assist in administering anaesthetics himself. Many purely practical points will then have to be learned: the selection of suitable cases tor anaesthesia; the preparation of the patient; the choice of the anaesthetic and of an inhaler; the position of the patient; the method of watching the face, eyes, pulse and respiration; the detection of unfavourable symptoms, and their immediate treatment; and, finally, the after treatment of the ease. All these and other matters connected with the administration of anaesthetics can be but briefly referred to in the following paragraphs: a. Selection of cases. - Chloroform must be given with great caution to the aged and infirm, to persons who are subject to attacks of faintness, or known to suffer from fatty degeneration or dilatation of the heart, to very fat and very anaemic persons, to epileptics, to chronic drunkards, to the subjects of extensive disease of the lungs or respiratory passages. Nitrous oxide gas or ether must be preferred in such subjects, according to the length of the operation. Valvular disease of the heart with compensation suggests special care, but is not a contraindication. Operations on the mouth, nose, throat, attended by possible bleeding into the glottis, demand special precautions, whether by great expedition, special postures of the patient, ox-even previous tracheotomy. It must never be forgotten, however, that when an operation is absolutely necessary, it can always be more safely performed with anaesthetics than without their aid; and that before the days of ether and chloroform, many persons died under an operation, from fear, faintness, and shock, the danger from which is completely removed or greatly diminished by anaesthetics.