Anesthesia is divided into three stages; the stimulant, anaesthetic and paralytic.

In the first stage there is struggling and excitement, due partly to the action of the drug and partly to fright. The local irritant action of the vapor causes choking and coughing, which also induces struggling.

The respiratory and cardiac centers are temporarily stimulated, as a consequence of which the pulse and respiratory movements are increased in force and frequency and blood tension is raised.

The smaller animals, particularly the dog, may vomit during the first stage of anaesthesia. In the first stage the dog may bark, whine or howl, the horse neighs and groans; other animals give expression to sounds more or less characteristic to their species.

The second or anesthetic stage is characterized by loss of consciousness, sensation, motion and partial loss of reflex action and is that state suitable for operations. The stimulating action of the anesthetic has passed and there is now depression of the cerebral functions, the motor centers. The voluntary muscles are completely relaxed, the sphincters occasionally, the patient lies absolutely motionless, the cornea fails to respond to irritation, i. e., winking is not produced when the cornea is lightly touched with the finger. Sometimes the muscles are rigid and twitching during this stage of anesthesia, though sensation and consciousness are absent. In the anesthesia stage the pulse is slow, full and strong, due to lowered blood pressure, the breathing is slow and shallow but regular.

The third or paralytic stage, which must be carefully watched against, poisoning is beginning and there is depression of the three great medullary centers controlling the heart, respiration and vascular tension and also the posterior reflex centers of the spinal cord, so that the urine and faeces are passed involuntarily. The passage of urine frequently occurs in the first stages of anesthesia and should not of itself be considered a danger mark. When the pulse becomes rapid, feeble and irregular, the breathing is at first stertorous and then the respiratory movements become shallow and weak, with long intervals intervening between them; this irregularity is a most important danger sign. The skin and mucous membrane often become cold and clammy. The pupils are usually widely dilated, though death may occur with either dilated or contracted pupils and consequently no dependence should be put in this sign unless there has been a sudden change from one condition of the pupils to the other. The three above mentioned stages are conventional, and are not in any case so clearly defined in practice as they are described theoretically upon paper. The first stage may be either absent or prolonged, and the last stage should not be reached at all.

COMPARISON OF ETHER WITH CHLOROFORM

Consequently you can see considering both drugs to be properly administered, all the advantages are in favor of chloroform except safety.

Ether is to be preferred for dogs, cats and other small animals.

Chloroform is especially dangerous for dogs, though horses stand it exceptionally well and it is preferable to ether in large animals. The safety with which chloroform may be administered to large animals frequently makes veterinarians careless; that is, they “force” the drug; they do not allow sufficient air for dilution, and though the patients may not die from the immediate effects of the drug their existence may be terminated in a few days from pneumonia or broncho-pneumonia (mechanical), due to the irritating effects of the drug.

Anaesthesia.—It is best to cast the large animals; after complete anaesthesia remove the hobbles.

For dogs make a cone of a towel and paper, put a sponge in the bottom, allowing a small opening in the end to admit air; pour in ether a little at a time.

In brain diseases or tumors of the brain, chloroform is dangerous. Horses with heaves or emphysema should not take chloroform; it is also dangerous in fatty degeneration of the heart. Operations during incomplete anaesthesia, especially with chloroform, are dangerous; always produce complete anaesthesia, have the stomach empty, but don’t fast animals for more than two or three meals.

Things to remember when administering an anaesthetic:

The operator must be skilled and give his attention exclusively to the production of anaesthesia, watching the respiration and pulse for signs of failure.

Do not commence operation until anaesthesia is profound, until reflex action is abolished, which can be told by touching the eye with the finger; obey this, no matter how slight the operation. The utmost care should be exercised if the patient is very old or has fatty degeneration of the heart, or lung diseases.

Great care should be exercised in operations about the mouth or trachea. See that no blood passes down the trachea. The stomach and bowels should be empty. This will cause less nausea and feed may be regurgitated and run down the trachea.

When purchasing chloroform or ether for anaesthetic purposes insist on the best; it must be pure.

Ether can be used almost pure, only a little air being necessarily allowed for dilution; chloroform must have a large amount of air.

In all classes of patients the head should be slightly raised, and watch the tongue so that it does not fall back over the larynx and suffocate the animal.

Anaesthesia should be started very slowly; don’t force either chloroform or ether.

It is a good practice to have restoratives ready for use before commencing anaesthesia, as aqua ammonia fort., a hypodermic syringe and nitro-glycerin.