The etiology is obscure. Often no cause can be found. Again, there is a history of some kidney involvement following one of the acute infectious diseases, or it may follow the nephritis of pregnancy. Usually, however, these cases fall into the group of secondary contracted kidneys, chronic parenchymatous nephritis.

Ill.u.s.trative Case.--R. Z., a woman, aged thirty-six years, was seen July 26, 1916, in coma. There was a history of typhoid fever at nineteen years, but no other disease. She had had nine full-term pregnancies, the last one thirteen months previously. For a week before the onset of the present illness she had complained of severe headaches and dizziness. There were no heart symptoms. For the past year she has had nycturia. Physical examination revealed tubular breathing beneath the manubrium, a few rales in the chest, an enlarged heart (left side), with a systolic murmur over the aortic area. Blood pressure was 178-125-53, the pulse rate 96, leucocytes 27,250. Venesection of 500 c.c. of blood and intravenous injections of 500 c.c. of 5 per cent NaHCO_3 in normal saline were employed.

Lumbar puncture withdrew 60 c.c. of clear fluid under pressure with 6 cells per cubic millimeter. The eye grounds showed distinct haziness of the disks and dilatation of the veins. Blood pressure after venesection was 164-122-42, pulse 76, but in a few days rose to 222-142-80, pulse 70. A second venesection of 400 c.c. and proctoclysis of 1000 c.c. saline solution was tried. The blood-pressure now was 198-140-58. The pH of the blood was 7.6, the alkaline reserve was 35 volume per cent (van Slyke), and the CO_2 tension of the alveolar air (Marriott) was 25 mm. The phthalein on the day following the second venesection was 45 per cent in two hours. The urine at first showed 500 c.c. in twenty-four hours, specific gravity 1016, alb.u.min and casts. Later she pa.s.sed 1300 to 1600 c.c. with specific gravity around 1010. The blood-pressure fluctuated considerably, reaching as low as 138-98-40, pulse 88. She was discharged improved September 10, 1916. She had constant headache but managed to keep up. In June, 1917, she suddenly died in an uremic coma.

Group B. This one might designate as the hereditary type, although there is not always a history in the antecedent. This group includes the robust, florid, exuberantly healthy people. They often are heard to boast that they have never had a doctor in their lives. They are usually thick-set or very large, fleshy people. The pressure picture is exceedingly high. The pulse pressure is moderately increased. The arteries are rather large, fibrous, and often quite tortuous, although this is not always the case. Some persons have hard, small, fibrous arteries. There is no puffiness beneath the eyes, no polyuria, and no nycturia as a rule. The urine is of normal amount, color, and specific gravity. Alb.u.min is only rarely found and then in traces, but careful search of a centrifuged specimen invariably reveals a few hyaline casts. The phthalein excretion is normal or only slightly reduced. The kidneys excrete salt and nitrogen normally. It is in this group that apoplexy is found most frequently. The rupture of the vessel occurs when the victim is in perfect health, often without any warning. Occasionally when such a case recovers sufficiently to be around, cardiac decompensation sets in later and he dies then of the cardiac complications.

Pathologically the hearts of such persons are found to have the most enormous hypertrophy of the wall of the left ventricle. The cavity is somewhat enlarged, as is always the case when the pulse-pressure is increased, but the size of the cavity is not the striking feature. The aorta is fibrous, thick walled, and the arch is slightly dilated. There are patches of arteriosclerosis. One such case seen only at autopsy had a rupture of the aorta just above the sinus of Valsalva and died of hemopericardium. The kidneys are of normal size, dark red, firm, the capsule strips readily, the surface is smooth or finely granular, the cortex is not decreased. The pyramids are congested and red streaks extend into the cortex. Microscopically the capsules of the glomeruli are a trifle thickened; a few show hyaline changes. There is rather diffuse, mild, round-cell infiltration between the tubules. The tubular epithelium shows little or no demonstrable changes. The arterioles are generally the seat of a moderate thickening of the intima and media, but it is not usual to find obliterating endarteritis. There is evidently a diffuse fibrous change which has not affected either the tubules or glomeruli to any great extent.

Ill.u.s.trative Case.--L. C., a man, aged fifty-six years, stonemason by trade, is a stocky, thick-necked individual. He had never been ill in his life until a year ago, when he fell from his chair unconscious. He had a right-sided hemiplegia which has cleared up so completely that except for a very slight drag to his foot he walks perfectly well. He came in complaining of shortness of breath and cough. There was no swelling of the feet. Here evidently was left-heart decompensation. Examination showed the blood pressure to be 240-130-110, pulse irregular, 104 to the minute. There were cyanosis and rales throughout both chests. The urine was normal in color, specific gravity 1025, small amount of alb.u.min, few casts, hyaline and granular. The phthalein elimination was 65 per cent in two hours. Under rest, purgatives, and digitalis he was much improved. He has since had two other apoplectic strokes, the last of which was fatal.

When these patients are seen with acute cardiac decompensation, there are, of course, much alb.u.min and many casts in the urine, and the phthalein output is, for the time being, decreased.

Group C. This might be called the arteriosclerotic high-tension group (Stone's cardiac group). The cases are usually over fifty years old.

They are men and women who have lived high and thought hard. Often they have had periods of great mental strain. Many men in this group were athletes in their young manhood. Many have been fairly heavy drinkers, although never drinking to excess. They are usually well nourished and inclined to stoutness. The pressure picture is high systolic with normal or only slightly increased diastolic and large pulse pressure. The arteries are large, full, fibrous, usually tortuous. The heart is very large, the apex far down and out. There is no polyuria; nycturia is uncommon, quite the exception. The urine is normal in color, amount, and specific gravity. Alb.u.min is only rarely found and hyaline casts are not invariably present. The phthalein excretion is quite normal and the excretions of salt and nitrogen are also normal. The terminal condition in most of the patients in this group is cardiac decompensation. They may have several attacks from which they recover, but after every attack the succeeding one is produced by less exertion than the preceding one, and it becomes more and more difficult to control attacks. Eventually the patients become bed- or chair-ridden, and finally die of acute dilatation of the heart.

Occasionally patients in this group may have a cerebral attack, but in my experience this is uncommon. Pathologically the heart is large, at times true _cor bovinum_, dilated and hypertrophied. The cavity of the left ventricle is much dilated. The aorta is dilated and sclerosed.

The kidneys are increased in size, are firm, dark red in color, with fatty streaks in the cortex. The capsule strips readily and the cortex is normal in thickness or only slightly increased. The organ offers some resistance to the knife. The microscope shows small areas scattered throughout where the glomeruli are hyalinized, the stroma full of small round cells, the tubules dilated, and the cells are almost bare of protoplasm. Naturally the tubules are full of granular cast material.

Also the arterioles show extensive intimal thickening, fibrous in character, with occasional obliterating endarteritis. One gets the impression that the small sclerotic lesions are the result of anemia and gradual replacement of scattered glomeruli by fibrous tissue. For the most part the kidney, except for the chronic pa.s.sive congestion, appears quite normal. One can readily understand that in such a kidney function could not have been much interfered with.

Ill.u.s.trative Case.--C. K., an active, stout, business man, aged fifty-six years, consulted me on account of shortness of breath and swelling of the feet in May, 1915. He had just returned from a hospital in another city, where he had gone with what was apparently cardiac decompensation. In his early manhood he had been a gymnast and a prize winner. He has worked hard, often given way to violent paroxysms of temper, has eaten heavily but drunk very moderately.

The heart was greatly enlarged, the arch of the aorta dilated, a mitral murmur was audible at the apex. The radials and temporals were large, tortuous, and fibrous. The blood pressure picture ranged around 180-90-90. He was easily made dyspneic and had a tendency to swelling of the lower legs. The urine was acid, of normal specific gravity, normal in amount, normal phthalein, normal concentration of salt and nitrogen, contained alb.u.min only when he was suffering from decompensation of the heart. Casts were always found. He finally died, after sixteen months, with all the symptoms of chronic myocardial insufficiency. The heart was enormous, a true _cor bovinum_. The kidneys were typical of this condition, possibly somewhat larger than usual.

=Hypotension=

When the pressure is constantly below the normal, it is called hypotension. This may be transient--as in fainting--it may be a normal state of the individual, it occurs in most fevers and in a great variety of diseases, including anemias.

In arteriosclerosis, especially the diffuse (senile) type, the blood pressure is invariably low, and may be spoken of as hypotension. The heart in such a case is small, the muscle is flabby, there is brown atrophy of the fibers, and some replacement of the muscle cells by connective tissue. The same causes which have produced general arteriosclerosis have also produced sclerosis of the coronary arteries, and probably the lessened blood supply accounts for much of the atrophy of the heart muscle.

In typhoid fever the maximum blood pressure during beginning convalescence may be as low as 65 mm. Hg. I have frequently seen hypotension of 80 mm. This is common.

Meningitis is the only acute infectious disease in which the blood pressure is more often high than low. This is accounted for by the increased intracranial tension.

Following large hemorrhages the blood pressure is reduced. In venesection the withdrawal of blood may not affect the blood pressure.

The procedure is done to relieve overdistension of the heart.

In pleurisy with effusion and in pericarditis with effusion there is hypotension.

Collapse, whether from poisoning by drugs or as the result of dysentery, cholera, or profuse vomiting from whatever cause, reduces the blood pressure.

In cachectic states, such as cancer, the blood pressure is low. General wasting of the whole musculature includes that of the heart and the heart muscle shows the condition known as "brown atrophy."

A most interesting and important condition in which hypotension occurs is pulmonary tuberculosis. Haven Emerson has recently gone over the whole subject in a careful piece of work and his summary is as follows:

"Hypotension or subnormal blood pressure is universally found in advanced pulmonary tuberculosis, in which condition emaciation may play a part in its causation. Hypotension is found in almost all cases of moderately advanced tuberculosis, or in early cases in which the toxemia is marked except when arteriosclerosis, the so-called arthritic or gouty diathesis, chronic nephritis, or diabetes complicate the tuberculosis and bring about a normal pressure or a hypertension. Occasionally the period just preceding a hemoptysis or during a hemoptysis may show hypertension in a patient whose usual condition is that of hypotension.

"Hypotension has been found by so many observers in early, doubtful or suspected cases with or before physical signs of the disease in the lungs, and is considered by competent clinicians so useful a differential sign between various conditions and tuberculosis, that it should be sought for as carefully as it is the custom at present to search for pulmonary signs.

"Hypotension when found persistently in individuals or families or cla.s.ses living under certain unhygienic conditions should put us on our guard against at least a predisposition to tuberculosis. Most unhygienic conditions, overwork, undernourishment and insufficient air, are of themselves causes of a diminished resistance, and it seems likely that a failure of normal cardiovascular response to exercise or change of position may be found to indicate this stage of susceptibility, especially to tuberculous infection.

"... Hypotension, when it is present in tuberculosis, increases with an extension of the process. Recovery from hypotension accompanies arrest or improvement. Return to normal pressure is commonly found in those who are cured. Continuation of hypotension seems never to accompany improvement. Prognosis can as safely be based on the alteration in the blood pressure as on changes in the pulse or temperature...."

There are a few drugs which lower the blood pressure, but, as a rule, their effects are more or less transitory. We know of no drug, unless it be iodide of pota.s.sium, which has the property of causing changes in the blood (decrease in viscosity?), which tends to reduce the blood pressure when it is excessive. This drug fails us many times.

SOME DRUGS WHICH INFLUENCE THE BLOOD PRESSURE

=Pressure Raisers=

Adrenalin, when injected directly into a vein or deep into the muscles.

The action is transitory.

Caffeine, preferably in the form of caffeine-sodium-benzoate. A good drug.

Strychnine, which does not act directly but seemingly through the higher centers.

Ergot, somewhat uncertain.

Nicotine, not used therapeutically.

Camphor, used in sterile olive oil and injected deeply into the muscles.

Digitalis, when the cardiac tone is low and decompensation is present.

Its action is prolonged but slow. Injections of the infundibular portion of the pituitary body. Not in use clinically.

=Pressure Depressors=

Nitroglycerine and amyl nitrite, action transitory but rapid.

Sodium nitrite and erythrol tetranitrate.

Action somewhat more prolonged.

Aconite, veratrum viride, chloral, etc. These depress the heart.

Purgatives, drastic and hydragogue.

Pota.s.sium and sodium iodide may lower blood pressure. When they do, the action is prolonged.

Diuretin and theocin-sodium-acetate.

=Venous Pressure=

Comparatively little work has been done upon the determination of the pressure in the veins in man. It is conceivable that this procedure may, at times, be of great value. A number of attempts have been made to measure the venous pressure by compressing the arm veins and noting on a manometer the force necessary to obliterate the vein. As the pressure is so slight, water is used instead of mercury, and readings have been given in centimeters of water.

[Ill.u.s.tration: Fig. 33.--Apparatus for estimating the venous blood pressure in man, devised by Drs. Hooker and Eyster. The small figure is the detail of the box B. See explanation in text.]