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Pneumonia.—The fact that the symptoms of death of children from pneumonia are largely those of vasomotor failure, makes the study of this reaction of particular importance. Howard and Hoobleri have studied the effect of fresh air on patients with acute pneumonia. They find that there is always a rise in blood-pressure following removal from a warm well-ventilated ward to the cold balconies of Bellevue Hospital. This rise is apparent at the expiration of a half hour or more, after removal, and reaches its maximum only after about two hours, remaining constant thereafter, even for thirty hours, and there was noted no tendency for the pressure to fall as if from exhaustion by the effort. Upon return to the warm wellventilated ward a fall is apparent in from fifteen to twenty minutes, usually reaching its lowest point in an hour, when it remains unless influenced by the course of the disease, by stimulation or by a return to out-ofdoors. They concluded that this rise of 10 or 15 mm. of mercury was due to the effect of the cold air upon the skin of the face and on the nasal mucous membrane, and not to the purity of the air.

Acute Nephritis.—Lenox Gordon reports nine cases of acute nephritis in all of which the blood-pressure was found to be above normal. In some cases this elevation is marked, becoming of distinct diagnositc value, as in no other disease of childhood is there to be found such a marked rise in pressure. As in adults, the pulse pressure has a tendency to be increased, owing to defective elimination and the consequent retention of toxic substances which directly affect the elasticity of the arterial walls and the permeability of the capillary system.

1 J. Howard and B. R. Hoobler, Am. Jour. Dis. of Children, May, 1912, üi, 5.

The frequent occurrence of general edema in this disease calls attention to the importance of the element of error introduced into pressure readings made through tissues where edema exists.

The Sphygmomanometer in Asphyxia Neonatorum.

Ballard' speaks highly of the value of the sphygmomanometer as a means of detecting the persistence of the fetal heart beats in babies born in asphyxia. He cites four cases, in which neither the radial pulse nor the heart beat could be detected, and yet in which the apparatus demonstrated slow brachial pulsations.

*P. Ballard, Presse Médicale, 1913, Mar. 22, No. 26.

CHAPTER XII

ACUTE INFECTIONS

In the study of infectious diseases, the routine use of the blood-pressure test offers an almost unlimited field of usefulness, which in the light of present knowledge, no physician can afford to neglect. Naturally this test offers little in the way of diagnosis, but for prognosis and as a guide to treatment it becomes a constant and a most reliable aid.

TOXEMIA AND BLOOD-PRESSURE

As a general rule, in acute infections in a robust individual, where the onset is sudden, there is noted an early rise in systolic pressure amounting to not more than 10 or 15 mm. Hg. During the course of the invasion, as the toxemia develops, there is a gradual fall in the systolic pressure level, in which the diastolic participates, usually to less extent, the result being a narrowing of the pulse pressure. As convalescence advances there is a gradual return to normal values. The degree of depression and the rapidity of the return of the convalescent's pressure to normal will be influenced by (a) the duration of the disease, (b) the profoundness of the toxemia, and (c) vitality and resistance of the patient. The depression is both marked and prolonged in typhoid fever and in pneumonia.

Complications may alter the picture in several ways. Thus, in convalescence from prolonged fevers, when the patient assumes the erect posture, the systolic pressure may be found to fall, while the diastolic may remain unchanged. This reduction in pulse pressure, tends to cerebral anemia which reflexly increases heart rate, thereby causing unnecessary cardiac strain. This probably explains the cardiac disturbances seen so often in convalescents from acute infections and which should be guarded against by frequent blood-pressure observations, permitting a gradual return to physical activity only when indicated by the findings. Even late in the convalescence or after apparent return to normal, physical exertion may cause the same disturbance, from which the heart may not recover for weeks or even months. So frequently is this condition encountered that R. N. Willson has said that we may state that there occurs probably no instance of perfect cardiac recovery from an acute micro-organismal invasion."

The incidence of renal irritation or of an acute nephritis during the course of an acute infection will speedily be accompanied by a sharp rise in systolic pressure even before urinary or other signs appear.

Violent purging and diarrhea will accentuate the usual fall seen during the progressive stages of acute infections. 2

Venous pressure tends to fall coincidently with the systolic during the active febrile stage, unless the heart becomes embarrassed, when the venous pressure rises and adds an additional burden to the already laboring heart.

In acute infections the basis for application of the test is the experimental evidence of the influence of bacterial

1 Penn. Med. Jour., December, 1914, Vol. iii, No. 12. a Nelson and Hyland, Jour. A. M. A., Feb. 8, 1913, lx, 6, p. 436.

poisons and toxemias on the vasomotor system. Sajous! has brought forward a theory of the relation of the adrenal gland to the dangerously low blood-pressure found in the terminal stages of acute infections, especially in pneumonia and typhoid fever. Sajous quotes Goldzicher who reaches the conclusion that in septicemia the appearance of low blood-pressure is to be ascribed to insufficiency of the adrenals. This relation, if found to be the true explanation, when generally recognized may yield a rich harvest of recoveries.

Methods of Study. In the study of infectious diseases, single observations are valueless because of the lack of normal figures for comparison. Careful daily observations should be made and recorded and if the pressure tends toward a dangerous hypotension, the periods of observation should be shortened to meet the requirement.

PNEUMONIA

The danger in pneumonia is largely cardiac. The bloodpressure is usually low. The toxic influence upon the vasomotor mechanism and upon the heart muscle may be such that this organ, in its weakened state, is unable to pump strongly enough to maintain an efficient arterial pressure, in the face of vasomotor relaxation. Unfortunately, we are not able to depend entirely upon the bloodpressure test as a guide to prognosis in pneumonia. Statistics are not in accord. It also appears that death occurs sometimes in cases showing higher pressure, while some recover with very low pressure, so that a low systolic pressure does not necessarily always have fatal import.

1 Monthly Cyclo. Med., December, 1911.

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