ANAESTHESIA (a privative, _____ sensation), a term in medicine used to describe a state of insensibility to external impressions, either as the result of disease or as induced artificially by the employment of certain sub-stances known as anaesthetics.
In diseases of the brain or spinal cord anaesthesia is an occasional symptom, but in such cases it is usually limited in extent, involving a limb or a definite area of the surface of the body. Complete anaesthesia has been observed in persons who were in a state of catalepsy or trance.
The artificial induction of anaesthesia by the use of drugs or the inhalation of vapours is a subject of great interest, both historically and from its practical application to the relief of suffering and the treatment of disease. Although it is mainly owing to the researches of distin-guished chemists and physicians of the present century that the employment of anaesthesia has come to occupy a foremost place among remedies, there is abundant evidence to show that it is a practice of great antiquity. Besides the mention by Homer of the anaesthetic effects of nepenthe, and the reference by Herodotus to the practice of the Scythians of inhaling the vapours of a certain kind of hemp to produce intoxication, the employment of anaesthetics in surgery by the use of mandragora is par-ticularly alluded to by Dioscoricles and Pliny. It also appears, from an old Chinese manuscript laid before the French Academy by M. Julien, that a physician named Hoa-tho, who lived in the 3d century, gave his patients a preparation of hemp, whereby they were rendered insensible during the performance of surgical operations. Mandragora was extensively used as an anaesthetic by Hugo de Lucca, who practised in the 13th century. The soporific effects of mandrake are alluded to by Shake-speare, who also makes frequent mention of anaesthetising draughts, the composition of which is not specified.
In the Medical Gazette, vol. xii. p. 515, Dr Sylvester, quoting from a German work by Meissner, published in 1782, mentions the case of Augustus, king of Poland, who underwent amputation while rendered insensible by a narcotic. But the practice of anaesthesia had never become general, and surgeons appear to have usually regarded it with disfavour. When, towards the close of last century, the brilliant discoveries of Priestley gave an impetus to chemical research, the properties of gases and vapours began to be more closely investigated, and the belief was then entertained that many of them would become of great medicinal value. In 1800, Sir Humphrey Davy, experimenting on nitrous oxide gas, discovered its anaesthetic properties, and described the effects it had on himself when inhaled, with the view of relieving local pain. He suggested its employment in surgery in the fol-lowing words :—" As nitrous oxide, in its extensive opera-tion, seems capable of destroying physical piain, it may probably be used with advantage in surgical operations in which no great effusion of blood takes place." His sug-gestion, however, remained unheeded for nearly half a century. The inhalation of sulphuric ether for the relief of asthma and other lung affections had been employed by Dr Pearson, of Birmingham, as early as 1785 ; and in 1805 Dr Warren, of Boston, U.S., used this treatment in the later stages of pulmonary consumption.
In 1818 Faraday showed that the inhalation of the vapour of sulphuric ether produced anaesthetic effects similar to those of nitrous oxide gas; and this property of ether was also shown by the American physicians, Godman (1822), Jackson (1833), Wood and Bache (1834).
These observations, however, appear to have been re-garded in the light of mere scientific curiosities and sub-jects for lecture-room experiment, rather than as facts capable of being apjjiied practically in the treatment of disease, till December 1844, when Dr Horace Wells, a dentist of Hartford, Connecticut, underwent in his own person the operation of tooth extraction while rendered insensible by nitrous oxide gas. Satisfied, from further experience, that teeth could be extracted in this way without pain, Dr Wells proposed to establish the practice of painless dentistry under the influence of the gas ; but in consequence of an unfortunate failure in an experiment at Boston, he abandoned the project. On 30th September 1846, Dr Morton, a dentist of Boston, employed the vapour of sulphuric ether to procure general anaesthesia, in a case of tooth extraction, and thereafter administered it in cases requiring surgical operation with complete success. This great achievement marked a new era in surgery. Operations were performed in America in nume-rous instances under ether inhalation, the result being only to establish more firmly its value as a successful anaesthetic. The news of the discovery reached England on 17th December 1846. On 19th December, Mr Bobinson, a dentist in London, and on the 21st, Mr Liston, the emi-nent surgeon, operated on patients anaesthetised by ether; and the practice soon became general both in Great Britain and on the Continent.
The late Sir James Y. Simpson, of Edinburgh, was the first to apply anaesthesia by ether in midwifery practice. This he did on 19th January 1847, and he subsequently employed ether inhalation in numerous cases of both easy and difficult parturition, an account of which he published, containing much important information. The results of his trials showed that while the anaesthesia annulled the conscious suffering's of the patient, it in no way interfered with the muscular contractions of the uterus and the pro-gress of the labour, and that it did not injuriously affect the child.
These observations excited great interest in the medical world, and led to the extensive employment of ether inhala-tion till November 1847, when Simpson announced his, discovery of the anaesthetic properties of chloroform (the trial of which had been suggested to him by Mr Waldie, a chemist of Liverpool), and proposed it as a substitute for sulphuric ether. So convincingly did he demonstrate the great advantages of chloroform, that this substance speedily superseded the use of ether as an anaesthetic, and continues to the present time probably the most widely-used of all the agents employed in medicine for the relief of human suffering.
As the result of further investigations in this depart-ment of scientific research, in which the labours of Dr Snow, Mr Nunneley, and Dr Richardson have been con-spicuous, numerous other volatile organic fluids have been found to possess anaesthetic properties. Several of these have been used in surgical practice, but as yet none of them have been found to possess such superiority as would entitle them to supersede chloroform.
There are many who prefer ether as being a safer anaes-thetic than chloroform, less apt to depress the circulation, and less apt to excite vomiting; but any advantage it has in these respects appears, in the estimation of surgeons, to be practically counterbalanced by the greater efficiency and facility of application of the latter substance. Ether, however, continues to be largely used in America.
When introduced by inhalation into the system, anaes-thetic vapours act upon the brain and sensory nerves in such a manner as more or less completely to abolish their natural sensibility. The degree in which they do this can be in large measure regulated by the quantity administered. Thus, taking the familiar instance of chloroform, the effect of the inhalation of a small quantity (say less than half a drachm) is a feeling of exhilaration or semi-intoxica-tion, accompanied with diminished sensibility to pain, but without entire loss of consciousness. By continuing the inhalation and increasing the quantity, profound stupor, stertorous breathing, fixing of the eyes, and muscular relaxation mark the occurrence of complete anaesthesia. In many cases it is desirable to produce merely the former of these conditions, viz., that of imperfect anaesthesia; and this is the extent to which chloroform is usually applied in un-complicated labour. On the other hand, in surgical opera-tions requiring absolute stillness on the part of the patient the inhalation must be carried to the extent of producing total unconsciousness. The state of anaesthesia can be safely kept up for long periods by continuing to apply, with due caution, the anaesthetic vapour. Whenever the inhalation is stopped, consciousness begins to return, and, in most cases, is soon completely restored.
The importance to the science of medicine of the intro-duction of anaesthesia can scarcely be over-estimated. By the employment of anaesthetics in surgery, not only is the work of the surgeon relieved of a source of embarrass-ment, and operations the most difficult and delicate under-taken which otherwise would have been impossible, but the death-rate in the worst cases has by universal testi-mony been greatly diminished. In no department of medicine has the use of anaesthetics been so extensive, or their value so manifest, as in midwifery. The power of chloroform in mitigating the pain attendant on ordinary labour, and in facilitating operative interference in cases of difficulty, is a matter of every-day experience in the practice of the accoucheur. In short, there is almost no condition of great physical suffering which may not be alleviated by the employment, under proper precautions, of anaesthetics. But if the boon has been great to medical science, it has been greater still to mankind; for not merely is an incal-culable amount of actual pain prevented, but the dread of submitting to surgical operations is beyond measure lessened by the thought that they can be performed while the sufferer is kept in a state of tranquil sleep.
Unfortunately, there is no known method of artificially producing insensibility which is entirely free from risk, and deaths have occasionally occurred under the adminis-tration of anaesthetic vapours. Like all medicinal sub-stances of a poisonous nature, the utmost care and watch-fulness are requisite in their administration. The clanger, cceteris paribus, is in proportion to the dose. It is more than probable that many of the fatal instances of anaes-thetic inhalation have been the result of carelessness; and it is certain that by a better acquaintance with the physio-logical action of the agents employed, and a closer observa-tion of the indications of danger in their use, the deaths may be greatly diminished. The importance of this has been recognised in many large hospitals, where the administration of anaesthetics is entrusted to one individual skilled in their properties and uses.
But it is doubtful whether many of the deaths occurring under anaesthesia can justly be ascribed to that cause. Sudden deaths occurring in the course of operations were by no means unheard of before anaesthetics came to be employed in surgery at all. Even, however, admitting that all the reported cases of death from anaesthesia are correct, it must be acknowledged that they are insignificant in amount, considering the enormous extent to which the use of chloroform and other anaesthetic agents prevails in all departments of medical practice.
The employment of local anaesthesia in surgery has the obvious advantage of being free from risk to life. Many means of accomplishing this have been suggested, the best known of which is the method of Dr Richardson, of the apjjlieation of ether spray to the part of the body which it is desired to render insensible. By the rapid evaporation of the ether the tissues become frozen, and insensibility of the part is produced. Since, however, the anaesthesia merely affects the superficial textures, this plan is only available in the minor operations of surgery, (j. o. A.)


Footnote

Nitrous oxide gas has been reintroduced, and is now extensively employed in dentistry.