This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Chloroform in many respects acts like alcohol; but it is more powerful. Thus if allowed to evaporate on the skin it produces cold; therefore the vessels at the point of application contract, and at the same time local anaesthesia is induced. If the vapor be confined, or if chloroform be rubbed into the skin, it acts as an irritant. The vessels dilate, the part becomes red, and there is a sense of heat. This rubefacient effect may pass on to vesication. It is a powerful antiseptic. Chloroform is an excellent antiseptic to preserve urine during transportation. Three drops, .20 c.c, to 4 oz., 120. c.c, of urine is sufficient. Allow the chloroform to evaporate before testing the urine.
Mouth. - If concentrated, it produces irritation and a burning sensation. If diluted, it has a sweetish taste, which renders Aqua Chloroformi a valuable vehicle for the administration of nauseous drugs. It reflexly gives rise to an increased secretion of saliva, and is a local anaesthetic.
The action of chloroform is very like that of alcohol. Large doses cause marked gastro-intestinal irritation. Small doses produce a feeling of warmth, dilatation of the gastric vessels, and increased secretion of gastric juice, and more regular and more powerful gastric movements. It is perphaps slightly astringent to the intestines.
It is absorbed into the blood from the stomach and intestines, and, if given as vapor, from the lungs; but it is very uncertain what changes it subsequently undergoes. Probably most of it is decomposed, but some is certainly eliminated in the breath and some in the urine, and it may be found in the blood of those who have been poisoned by it.
The internal temperature falls about 1° F. 0.50 C after the prolonged administration of chloroform.
Chloroform is an excellent instance of the law of dissolution (see p. 104), and also of the well known fact that drugs which, in small doses, stimulate any part, in large doses often depress it. The phenomena resulting from the inhalation of chloroform are commonly divided into three stages.
This is, at first, one of general stimulation, the highest functions being the most stimulated, usually unevenly, so that the patient is somewhat incoherent. The imagination is momentarily excited, and he experiences a general feeling of warmth and comfort spreading over the entire body. The mind, from the irregular excitation, is confused. Sight and hearing are stimulated, he experiences sensations of light and hears noises. The stimulation of all these higher functions is very transitory, and he quickly begins to lose consciousness; he may be aware that people around him are talking without knowing what they are saying, but soon he hears and sees nothing. Sometimes during the early part of this stage he may laugh or cry. The inability to see and hear is quickly followed by considerable blunting of general sensation. At the same time that these higher functions are being depressed the lower motor functions are excited; he will kick and fight, throwing his arms and legs about, so that much strength may be required to hold him down, and he will shout and talk incoherent nonsense very louldly. Almost coinci-dently the stimulation of the lower centres sets in; the pulse is increased in frequency, and there is throbbing of the heart and great vessels. The first inhalation or two may produce a choking sensation and a stoppage of breathing, which is often voluntary; but soon the respirations are increased in frequency. The blood-pressure at first rises a little, and the face may be flushed. The pupils usually dilate.
This is best called that of depression. Some authors call it the stage of excitement, because the excitation of the motor centres may be continued into it. It is important to remember that there is no sharp boundary-line between the various stages, they pass insensibly into one another. In this stage the depression of the highest functions continues, so that the patient becomes completely unconscious, and he appears to be in a deep sleep. He sees, hears and feels nothing, hence chloroform is called a general anaesthetic. The excitement of the motor functions passes into depression, and he ceases to shout and struggle. Some of the reflex centres are depressed, so that when the cornea is touched the eye does not shut. The pupil is contracted. The stimulation of the cardiac and respiratory apparatus gives way to depression, the pulse and respiration become less frequent and less strong. The vaso-motor centre is depressed, blood-pressure falls. As he cannot feel pain, and the reflex activity is so lowered that the heart will not be reflexly inhibited by the shock of an operation, this is the period at which to operate safely.
In this there is a total abolition of reflex excitability. Even the lowest reflex centres of the cord are depressed, so that the patient may pass his urine and faeces involuntarily; all muscular tone is abolished, and consequently the muscles are quite flaccid. Some of them, as those of the arm, were probably in this condition towards the end of the second stage. The pupil is widely dilated, probably because of the commencing asphyxia. This is the period to which the administration is pushed to facilitate the reduction of dislocations, or to enable the abdominal viscera to be felt through the abdominal wall. If still more chloroform is given the depression of the cardiac, respiratory and vaso-motor centres continues, the pulse becomes feeble and irregular, and the heart finally stops in diastole. At last not only its central nervous apparatus, but its muscular tissue is depressed, so that it will not respond to mechanical stimulation. The respiratory movements become slight and irregular, with very long pauses between them, and as a result the patient is more or less asphyxiated. The blood-pressure gradually falls to zero. There has been much dispute as to whether chloroform kills by the heart or the respiration. The Commission appointed by the Nizam of Hyderabad reported that it killed by depression of the respiratory centre, that respiration always failed before the heart, and that the fall of blood-pressure was not due to any effect on the heart. But their results have been disputed, and it has been shown that the fall of blood-pressure is mainly due to a weakening effect on the heart. In the United States it has been generally believed that death is from depression of the heart.
The recovery from chloroform also illustrates the law of dissolution. The lowest functions, such as muscular tone, are the first to reappear; but the patient does not usually regain his mental equilibrium for hours.
With the exception of its local action on the skin and alimentary canal, and its last effect on the cardiac muscle, chloroform acts entirely on the central nervous system, and this action is not the result of any effects on the blood. The peripheral nerves are not affected, unless it be just before death. Chloroform narcotizes infusoria.
Vomiting is very liable to occur during the administration of chloroform, and its advent is often made known by pallor and ' wide dilatation of the previously contracted pupil. Immediately before death the pupil may be either dilated or contracted.