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Norwegian city is 55,500, with 7,326 children in the public schools, and 1,169 in other schools. All these children appeared at the clinics in 1922, and ninety-eight per cent. of them came for treatment. The Norwegian regulation insists that dental treatment at the clinics be given to all children, and this shall be compulsory unless the child has private treatment. It will be seen that only two per cent. depended on their own dentists.

The authorities,note a marked improvement in the health of the school children since regular dental clinics have been instituted. Not only has the general health been bettered, which is a financial gain to the community, but there is much less absenteeism, which is another economic gain. Further than this, it is noted that there is improvement in the teeth of the children, for of the ninety-eight per cent. presenting themselves for observation in 1922 there were only about sixty-five per cent. really in need of treatment. This would leave a full third of the school children with perfect dental conditions, and when this is compared with the ninety-five per cent. of the children with one or more defects among Americans, the contrast is great.

The municipality of Trondhjem furnishes the service free as it does the educational portions of the school exercises, the cost being approximately two dollars a child a year. It is a measure of prevention and protection that any community could afford to undertake, and which would return the capital expended in the greater efficiency of the children, economy of effort in teaching them, and a better return from them in service to the city when they become grown-ups.-Selected.

THE HEART AND LIFE INSURANCE

Dr. Lewellys F. Barker concludes a contribution to Practical Medicine and Surgery, with the following summary:

1. In examining the heart, decisions as to standard risks can fairly safely be made from a consideration of the history of the patient, from determination of the site of the apex beat, from auscultation of the heart that excludes murmurs, and from consideration of the pulse and blood pressure.

2. For safe judgment of substandard risks a thorough diagnostic survey of the patient is desirable with utilization of modern methods of cardiovascular investigation (roentgenological, electrocardio graphic, metabolic, functional).

3. Recent graduates of our better medical schools have received training in these newer methods of investigation or know how to utilize the findings of special examiners.

4. Medical directors of life insurance companies would do well to consider the advisability of comprehensive diagnostic surveys before the insuring of sub-standard risks and perhaps for the insurance of supposedly standard risks if the amounts of the policies are large.

5. Internists look forward eagerly to the contributions to prognosis that medical actuaries can give in the future when they are able to analyze the effects upon longevity of deviations from normality in the cardiovascular stripe recognizable by the newer methods of examination.

SIGNIFICANCE OF HYPOTENSION

JOHN G. McLAURIN, M.D., DALLAS, TEXAS.

The purpose of this paper is to emphasize the importance of a symptom which has been somewhat overlooked by the profession, and to attempt to explain its causes under various circumstances. Probably the reason for the apparent neglect in studying the question of hypotension, is that hypertension has been such a problem that it has been well worthy of constant consideration. As a matter of fact, hypotension is just as much of a symptom as hypertension, and is associated with almost as many abnormal conditions which are capable of producing as much annoyance to the patient as hypertension. It is very likely true that patients with low blood pressure are more uncomfortable than those with high blood pressure, unless the high pressure is extreme.

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It is necessary to determine what is meant by hypotension. Of course age plays a considerable part, but I believe that a person at thirty-five years of age should not have a pressure below 110 m.m. of mercury systolic. It is not so easy to say just what should be designated as diastolic hypotension. other words, if a person at the age of thirty-five has a systolic pressure below 110, it is probable that some abnormality in his general condition has produced a low pressure, and we should look for the cause of it just as readily as we should look for the cause of high pressure.

The exact cause and mechanism of hypotension is somewhat doubtful at this time. I feel that it is just as important

to determine the cause of it as it is to determine the cause of leucocytosis, where we have not located our infection. There are not so many variations from day to day in hypotension, as in cases presenting hypertension. It is a fairly constant symptom in some cases, which fact indicates that the cause of it is also fairly constant, and will remain so until corrected. Dr. Lewellys Barker calls attention to the fact that persistent hypotension is found due to the loss of arterial tonus, rather than cardiac failure. It is common in (a) acute infections, (b) pulmonary tuberculosis, (c) surgical shock, and (d) chronic wasting diseases of various sorts.

(a) In acute infections the hypotension is usually due to the toxin effect on the vasomotor centres with resulting dilatation of the arterioles. Frequently is this seen in typhoid fever, pneumonia and peritonitis. The low pressure is likely to be more marked at the height of the fever. Meningitis is one of the few infections with a hypertension, and this is probably due to the fact that we are dealing with an increased intra-cranial pressure.

(b) In pulmonary tuberculosis the pressure is usually 20 to 40 m.m. below what should be expected in healthy people of the same age. Here also we are dealing with a toxin action on the vasomotor centre, and we are likely to have a degree of progressive atrophy to the heart muscle. If the tuberculosis should be associated with a plural effusion, the withdrawal of the effusion produces a fall of from 15 to 25 m.m. of mercury, depending somewhat upon the extent of the effusion.

(c) In surgical shock the fall in blood pressure is likely due to an exhaustion of the vasomotor centres of the brain cells, due to the great number of violent sensory impulses. This is Crile's theory, but Yandell Henderson believes that there is a diminished hemic osmotic tension due to a loss of carbon dioxide from the blood, and this allows a transudation of fluid into the tissues with a resulting lack of fluid in the circulation.

(d) Hypotension and tachycardia are nearly always seen in cachexias associated with anemia and brown atrophy of the heart.

Blood pressure is probably controlled by, first, the force of the heart action; second, condition of the blood vessels; third, the influence of supra-renal secretions; and fourth, by the amount of blood (only to a small extent unless the amount is greatly reduced). The force of the heart action depends

upon the strength of the heart muscle, and even in cases of dilated heart we may get either a hyper or a hypotension. This is probably explained by vasomotor control, and the vasomotor control in turn, may depend to a marked degree upon the amount of adrenal secretions. It has been proven that a prolonged low arterial pressure will produce a weak contraction of the heart muscle. Acute infections frequently give a low pressure, because of the vasomotor disturbances resulting from toxins and probably also from the toxic effect upon the adrenals, resulting in a diminished secretion from the glands, and not so much from the toxic effect on, or direct infection of the heart muscle itself. It is frequently desirable to have a low tension in typhoid fever, for in event of hemorrhage there is a better chance that the bleeding will be controlled. Probably in this disease the vasomotor control is disturbed by the toxins from the infection and the low pressure does not likely depend upon a toxic myocarditis. Pneumonia may also give a low pressure, but it is not always a bad sign in prognosis, even if the pulse rate has increased.

The condition of the vessels is next to be considered. The elasticity of the arteries does not determine the systolic pressure, though it probably has much to do with the diastolic pressure. An arterial sclerosis may exist with a hypotension, in fact, there is frequently a pronounced sclerosis with a systolic hypotension. Only in aortitis does the condition of the artery itself determine the pressure almost to a certainty, which pressure is usually low, especially in the diastolic reading.

The change in size of the arterioles probably controls the pressure more than the changes in other vessels, for it has been definitely determined that the greatest fall in the pressure occurred in the smaller arteries and capillaries. The veins may become enlarged, and in that way the amount of blood supplied to the heart be diminished. This may have some effect on the pressure, but in itself probably the effect is not the cause for a very appreciable change. After all, probably the effect of a disturbed nerve control to the vessels, and the effect of the internal secretions are the chief factors in the changes of pressure, so far as the vessels are concerned.

Thomas McCrae has found that "5 cc of blood per kilogram of body weight can be removed without producing any change in pressure, but subsequent removal of similar amounts produces a fall which increases in extent." At first

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there is no change because we get a compensatory vasoconstruction. In other words, if it was decided to bleed a patient weighing 60 kilograms, or approximately 150 pounds, there would probably be no reduction in pressure until more than 300 ce's of blood had been removed. Many times the hypotension following hemorrhage is distinctly advantageous, as can readily be seen in cases of injury where there will then be a greater tendency for the blood to coagulate.

Where the viscosity of the blood has been lowered, the pressure will also probably be lowered, due to the fact that the blood can more readily pass through the small vessels, therefore, if it is desirable to obtain a rise in blood pressure following shock where there has been a hemorrhage, it would be well to add some preparation such as gum acacia or gelatin to the saline solution intended for the intravenous infusion.

A reduction in the cellular elements is not likely to act directly in reducing the pressure, but probably the degree of starvation of the heart muscle resulting therefrom, and a diminished vascular tone, causes a certain amount of hypotension. It may be that the poorly nourished adrenals have some effect in these cases in reducing the pressure.

Hypotension may be found in cases of acidosis. This is probably due to the loss of tone in the heart muscle and arterial walls, which causes a slowing of the blood flow through the capillaries. This in turn causes a diminished oxidation, and there is a greater relaxation of the heart and vessels. This situation may, therefore, become a very serious one unless the acidosis can be overcome promptly.

In acute infections we often get a fall in blood pressure which may be due in part to the condition of the myocardium, and, as has already been stated, to the loss of the vessel tone, resulting from toxins. Just which of the two factors plays the most important part in the role is hard to determine in most instances. Probably some of the infections have a lower pressure from one cause, and in other infections the hypotension is caused in other ways. Digitalis is often given to increase the muscle tone, and thereby raise the pressure, but frequently the pressure does not come following the administration of this drug. On the other hand a cool tub bath or a sponge bath will likely be followed by a rise, due to a stimulation of the vascular tone. In this regard, let me point out that the mechanism of loss in the vessel tone has never been positively determined, for it has never been ascertained whether

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