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Essay on Anæsthesia*
The Veterinary Jountal. use of anc:esthetics will become as general in veterinary as in human surgery, and when the owners of animals will demand their employment as a right. In conclusion, I would wish to draw attention to an excellent and instr~ctive paper on "The Chloroform Question," by Dr. Lauder Brunton, which is now appearing in the L a-:1cet. It will well repay p erusal by all practitioners wh o are interested in the subject, as it embodies all th at is known by the highest authorities on the question of chloroform, from both experimental and clinical s.ources. ESSAY ON ANlESTH ESIA." BY M R. T. R . MULCAHY.
(Co1t#mted from page 32.)
Chloroform is chemically trichloromethane, and helongs to a series of products obtained from marsh gas, by substituting a molicule of chlorine for one of hydrogen, all of which h ave anc:esthetic properties. The m ethylated form is most used in veterinary practice on account of its cheapness, a nd answers· the purpose just as well. The susceptibility of individuals, even of the same species, varies so much, that it i.s most important th at the administrator be able to identify the different phenomena that may appear during the inhibition of the drug. The principal action of g en eral anc:esthetics, as b efore stated, is on the central nervous system, and it is divided into three stages. The higher centres are first acted on, and upon thi s depends. the safety of these drugs. F zrst S tage.-This may be called one of stimulation, a nd it will be observed that the first effect of chloroform and its congeners is always one of stimulation. The cells of the cerebral convolutions are first acted on. Stimulation of these cells causes excitement, but a ccompanied with more or less confusion. In the human subject the senses are at first exalted, but speedily become dulled. This is not so easily recognised in animals, but may be identified in the dog by the animal uttering sharp yelps of a delirious character. Muscular stimulation is also induced; this is of s horter duration in the case of chloroform than of ether, and is attributed partly to the actions of the drug on the convolutions, and partly to stimulation of the muscula r centres. It may b e diminished by the previous injection of morphia. * Read before thc Edinburgh Veterinary Medical Society.
Essay on Anasthesia. It must be remembered, however, that morphia depresses the h eart and also prolongs n a rcosis. Consciousness g radually becomes diminished, respiration is quicken ed, but the act is not so powerfully performed. The pulse a lso becomes more rapid, and perspiration may break out over the body; this, however, m ay be present from t h e first, if the animal h as been cast. The sympathetic is stimulated and the pupil dilates sl ightly . As chloroform first s timulates and then depresses, .and as it acts first on the higher centres, the centres in the cerebrum are d epressed, while those in the medulla a re b eing stimulated . H ence w e notice acceleration of the pulse and r espirations with diminished consciousness. S econd Stage.- This is one of depression and goes on to arrest of function. Consciousness ceases and the patient seems to b e in a h eavy stupor. Ordinary methods fail to produce r eflex stim ulation. The paniculus in the horse no longer responds to the touch of the h and . The reflex and so-called automatic excitability Df the cord and m edulla b ecome depressed, and hence the parts govern ed are disordered. The voluntary muscles become relaxed, but the pregnant uterus still continues to contract. This circumstance adds t b the value of these agents .during painful parturition. It may here be added that chloroform will often cause relaxation of the "os uteri " when all oth er methods have failed. The pupil contr acts gradually and fully, due to depression Df the sympathe tic. The respiratory centre becomes depressed, causing slow, shallow, noisy, and laboured breathing. The cardiac centre is also d epressed, ilnd, as a result, the pulse becomes slow a nd weak. This is the time to operate if the operation be a severe one (the administration of the drug b ein g discontinu ed), but for slight operations it is not ~ e ce ssary to go so far. As before m entioned, some say the tIme to operate is when the conjunctiva refuses to respond to the t?u ch of the finger. I should most certainly never advise pushmg the drug so far as this, as it must necessarily be beset w ith g reat danger . . Con sc ious~ess, at this stage , is completely arrested, but the VItal c~ ntres III the m edulla being lower, ate m erely depressed, a nd th1s rlepression is within safe limits. In th ~ ?og, vomition may occur after the stage of excitement; If It should, the mouth must be e mptied, and care must be t aken that n one of the ejecta finds its way into the t r ach ea .
The ' Veterinary Journal. The phenomena of the second stage are transient if the administration be discontinued; therefore, it may be necessary to apply some more chloroform if the operation be unfinished: for this purpose the operator should always have an assistant. Thz"rd Stage.-Beyond the second stage ancesthesia is extremely dangerous. The third is marked by complete loss of excitability of the medulla and cord, and thus the vital functions are depressed beyond the limits of safety. Respiration is almost arrested, and the effects of the drug are thus complicated by the presence of much venous blood in the system. The pulse becomes very weak and fluttering, the cutaneous vessels dilate, and pressure is reduced to mi. The lower centres governing the sphincters become depressed, and the animal may micturate involuntarily. Dogs may micturate at the commencement, from excitement, but this is not likely to be taken as a sign of danger. All the muscles relax, the pupil dilates widely, due in this case to paralysis of the third nerve. As before stated, however, the phenomena of the pupil are not constant. Death may occur through the heart, respiration or both. The heart ceases in diastole from central or nervo-muscular depression. Doses depend very much on the mode of administratibn. Horses and cattle usually take 2 OlS. to 6 OlS., dogs t Ol. to I oz. Modes of deatlz.-Sudden death at the beginning of administration is supposed by Bartholow to be due to paralysis of the cardiac ganglia by the first vapour, or it may be due to shock or over stimulation of the inhibitory nerve. Death may also occur from cardiac paralysis during the stage of insensibility. This is said to be due to the loss of control over the lower centres by the cerebrum. The heart in this case . ceases before respiration. This rarely occurs in the lower animals. Secondly, death from tetanic spasm of the respiratory muscles occurs when the muscles become rigid. It causes accumulation of venous blood in the right side of the heart, and thus arrests its action. In this case the heart continues to beat after respiration has ceasen. Thirdly, death by paralysis of the respiratory muscles may occur in the stage of complete muscular relaxation, but it will be obvious that ancesthesia should not be carried so far. Restoratory M easures.-Restoratives should be always kept at hand in. case of need. If the mucous membrane becomes pale, and the pulse very weak, cardiac failure may be feared.
Further Observations on Antivenene, etc.
159
The administration must be at once discontinued and amyl nitrite applied to the n ostril s. Inj ections of ether a re also of great value in threaten ed cardiac failure. If respir ation becom es shallow and weak, a nd the mucous membrane purple, cold water should be dash ed over the body and ammonia applied to the nostril s; a ll impediments to respiration r emoved, the tong ue drawn forward in a nimals that can breathe through the mouth. Fresh air is of course the most v.aluable. Artificial respira tion sh ould b e resorted to if practicable. Animals have been resuscitated by keeping the lungs inflat ed by means of a pair of b ellows until the vapour was excr ete d. I may mention h ere that when the operation is finished the patier.t, if down, should be ma d e to lie until the effects have in som e measure passed off. Cold water may be dashed over the h ead and body t o expedite r ecovery. The animal should be assist ed to rise, and supported for some little time when up. Knee-caps should b e always put on before the animal attempts to rise. P ost-J1,£ortem.- There are no constant post-mortem appearances in cases of death from chloroform. There may be signs of asphyxia or congestion of the lungs, but even these may be absent. If the vapour cannot b e detected by the sense of smell, analysis of the tissues may be attempted in the following manner; - The tissu es supposed to contain chloroform are put into a flask and distilled at a t emperature of 160°F. a nd the vapour passed throug h a tube heated to r edness. If chloroform b e present, it will b e split up into chlorine and hydrochloric acid. Th e acid reddens blue litmus and the chlorine can be detected by its setting iodine free from iodide of potassium, the iodide being d et ect ed by its action on starch solution. (To be continued. )
FURTHER O BSERVATIONS ON ANTIVENENE, AND ON THE PRODUCTION OF IMMUNITY AGAINST SERPENTS' VENOM; WITH AN ACCOUNT OF THE ANTIDOTAL PROPE RTIES OF THE BLOOD SERUM OF VENOMOUS SERPENTS. 'if BY PROFESSOR F RASER, M. D., F.R.S.
(Continued from page 99.)
Influence oj Dz'et zix modifyzng the Mznz71Zunz-L d hal Dose.I have already drawn attention to the r emarkable difference in the minimum-lethal dose of venom for herbivorous as contrasted with carnivorous animals. If this difference be
(Co1t#mted from page 32.)
Chloroform is chemically trichloromethane, and helongs to a series of products obtained from marsh gas, by substituting a molicule of chlorine for one of hydrogen, all of which h ave anc:esthetic properties. The m ethylated form is most used in veterinary practice on account of its cheapness, a nd answers· the purpose just as well. The susceptibility of individuals, even of the same species, varies so much, that it i.s most important th at the administrator be able to identify the different phenomena that may appear during the inhibition of the drug. The principal action of g en eral anc:esthetics, as b efore stated, is on the central nervous system, and it is divided into three stages. The higher centres are first acted on, and upon thi s depends. the safety of these drugs. F zrst S tage.-This may be called one of stimulation, a nd it will be observed that the first effect of chloroform and its congeners is always one of stimulation. The cells of the cerebral convolutions are first acted on. Stimulation of these cells causes excitement, but a ccompanied with more or less confusion. In the human subject the senses are at first exalted, but speedily become dulled. This is not so easily recognised in animals, but may be identified in the dog by the animal uttering sharp yelps of a delirious character. Muscular stimulation is also induced; this is of s horter duration in the case of chloroform than of ether, and is attributed partly to the actions of the drug on the convolutions, and partly to stimulation of the muscula r centres. It may b e diminished by the previous injection of morphia. * Read before thc Edinburgh Veterinary Medical Society.
Essay on Anasthesia. It must be remembered, however, that morphia depresses the h eart and also prolongs n a rcosis. Consciousness g radually becomes diminished, respiration is quicken ed, but the act is not so powerfully performed. The pulse a lso becomes more rapid, and perspiration may break out over the body; this, however, m ay be present from t h e first, if the animal h as been cast. The sympathetic is stimulated and the pupil dilates sl ightly . As chloroform first s timulates and then depresses, .and as it acts first on the higher centres, the centres in the cerebrum are d epressed, while those in the medulla a re b eing stimulated . H ence w e notice acceleration of the pulse and r espirations with diminished consciousness. S econd Stage.- This is one of depression and goes on to arrest of function. Consciousness ceases and the patient seems to b e in a h eavy stupor. Ordinary methods fail to produce r eflex stim ulation. The paniculus in the horse no longer responds to the touch of the h and . The reflex and so-called automatic excitability Df the cord and m edulla b ecome depressed, and hence the parts govern ed are disordered. The voluntary muscles become relaxed, but the pregnant uterus still continues to contract. This circumstance adds t b the value of these agents .during painful parturition. It may here be added that chloroform will often cause relaxation of the "os uteri " when all oth er methods have failed. The pupil contr acts gradually and fully, due to depression Df the sympathe tic. The respiratory centre becomes depressed, causing slow, shallow, noisy, and laboured breathing. The cardiac centre is also d epressed, ilnd, as a result, the pulse becomes slow a nd weak. This is the time to operate if the operation be a severe one (the administration of the drug b ein g discontinu ed), but for slight operations it is not ~ e ce ssary to go so far. As before m entioned, some say the tIme to operate is when the conjunctiva refuses to respond to the t?u ch of the finger. I should most certainly never advise pushmg the drug so far as this, as it must necessarily be beset w ith g reat danger . . Con sc ious~ess, at this stage , is completely arrested, but the VItal c~ ntres III the m edulla being lower, ate m erely depressed, a nd th1s rlepression is within safe limits. In th ~ ?og, vomition may occur after the stage of excitement; If It should, the mouth must be e mptied, and care must be t aken that n one of the ejecta finds its way into the t r ach ea .
The ' Veterinary Journal. The phenomena of the second stage are transient if the administration be discontinued; therefore, it may be necessary to apply some more chloroform if the operation be unfinished: for this purpose the operator should always have an assistant. Thz"rd Stage.-Beyond the second stage ancesthesia is extremely dangerous. The third is marked by complete loss of excitability of the medulla and cord, and thus the vital functions are depressed beyond the limits of safety. Respiration is almost arrested, and the effects of the drug are thus complicated by the presence of much venous blood in the system. The pulse becomes very weak and fluttering, the cutaneous vessels dilate, and pressure is reduced to mi. The lower centres governing the sphincters become depressed, and the animal may micturate involuntarily. Dogs may micturate at the commencement, from excitement, but this is not likely to be taken as a sign of danger. All the muscles relax, the pupil dilates widely, due in this case to paralysis of the third nerve. As before stated, however, the phenomena of the pupil are not constant. Death may occur through the heart, respiration or both. The heart ceases in diastole from central or nervo-muscular depression. Doses depend very much on the mode of administratibn. Horses and cattle usually take 2 OlS. to 6 OlS., dogs t Ol. to I oz. Modes of deatlz.-Sudden death at the beginning of administration is supposed by Bartholow to be due to paralysis of the cardiac ganglia by the first vapour, or it may be due to shock or over stimulation of the inhibitory nerve. Death may also occur from cardiac paralysis during the stage of insensibility. This is said to be due to the loss of control over the lower centres by the cerebrum. The heart in this case . ceases before respiration. This rarely occurs in the lower animals. Secondly, death from tetanic spasm of the respiratory muscles occurs when the muscles become rigid. It causes accumulation of venous blood in the right side of the heart, and thus arrests its action. In this case the heart continues to beat after respiration has ceasen. Thirdly, death by paralysis of the respiratory muscles may occur in the stage of complete muscular relaxation, but it will be obvious that ancesthesia should not be carried so far. Restoratory M easures.-Restoratives should be always kept at hand in. case of need. If the mucous membrane becomes pale, and the pulse very weak, cardiac failure may be feared.
Further Observations on Antivenene, etc.
159
The administration must be at once discontinued and amyl nitrite applied to the n ostril s. Inj ections of ether a re also of great value in threaten ed cardiac failure. If respir ation becom es shallow and weak, a nd the mucous membrane purple, cold water should be dash ed over the body and ammonia applied to the nostril s; a ll impediments to respiration r emoved, the tong ue drawn forward in a nimals that can breathe through the mouth. Fresh air is of course the most v.aluable. Artificial respira tion sh ould b e resorted to if practicable. Animals have been resuscitated by keeping the lungs inflat ed by means of a pair of b ellows until the vapour was excr ete d. I may mention h ere that when the operation is finished the patier.t, if down, should be ma d e to lie until the effects have in som e measure passed off. Cold water may be dashed over the h ead and body t o expedite r ecovery. The animal should be assist ed to rise, and supported for some little time when up. Knee-caps should b e always put on before the animal attempts to rise. P ost-J1,£ortem.- There are no constant post-mortem appearances in cases of death from chloroform. There may be signs of asphyxia or congestion of the lungs, but even these may be absent. If the vapour cannot b e detected by the sense of smell, analysis of the tissues may be attempted in the following manner; - The tissu es supposed to contain chloroform are put into a flask and distilled at a t emperature of 160°F. a nd the vapour passed throug h a tube heated to r edness. If chloroform b e present, it will b e split up into chlorine and hydrochloric acid. Th e acid reddens blue litmus and the chlorine can be detected by its setting iodine free from iodide of potassium, the iodide being d et ect ed by its action on starch solution. (To be continued. )
FURTHER O BSERVATIONS ON ANTIVENENE, AND ON THE PRODUCTION OF IMMUNITY AGAINST SERPENTS' VENOM; WITH AN ACCOUNT OF THE ANTIDOTAL PROPE RTIES OF THE BLOOD SERUM OF VENOMOUS SERPENTS. 'if BY PROFESSOR F RASER, M. D., F.R.S.
(Continued from page 99.)
Influence oj Dz'et zix modifyzng the Mznz71Zunz-L d hal Dose.I have already drawn attention to the r emarkable difference in the minimum-lethal dose of venom for herbivorous as contrasted with carnivorous animals. If this difference be