The Effect Of Drugs On Blood Pressure


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Sources: Disturbances Of The Heart

Free catharsis is a well established and valuable method of

relieving the heart in many cases of broken compensation, and in

cases with high blood pressure even while compensation is still

good, salines administered once or twice a week assist in

elimination, and in the reduction of blood pressure.



However, profuse purging in heart disease may be followed by

unfavorable symptoms, especially when the systolic blood pressure is

low. When there is hypotension, or when the diastolic pressure is

high and the venous pressure is high, and when there is edema or

effusion, watery catharsis should be caused only after due

consideration, and always with a careful watching of the effect on

the heart and blood pressure. The blood pressure is lowered by such

catharsis, and the heart is often slowed. Neilson and Hyland

[Footnote: Neilson, C. H., and Hyland, R. F.: The Effect of Strong

Purging on Blood Pressure and the Heart, THE JOURNAL A. M. A., Feb.

8, 1913, p. 436.] studied the effect of purging on the heart and

blood pressure, and were inclined to the view that in serious heart

conditions brisk purging should not be done. They think that the

slowing of the heart after such purging may be, due to an increased

viscosity of the blood, or perhaps to a reflex irritation from the

purgative on the intestinal canal.



Pilcher and Sollmann [Footnote: Pilcher and Sollmann: Jour.

Pharmacol. and Exper. Therap., 1913, vi, 323.] have shown that the

fall of blood pressure after the administration of nitrites is

mostly due to the action of these drugs on the peripheral vessels.

Chloroform, of course, depressed the vasomotor center, but ether had

no effect on this center, or slightly stimulated it. Such

stimulation, however, Pilcher and Sollmann believe may be secondary

to asphyxia. Nicotin they found to cause intense stimulation of the

vasomotor center. Ergot and hydrastis and its alkaloids seem to have

no effect on the vasomotor center. Strophanthus acted on this center

only moderately, and digitalis very slightly, if at all. Camphor in

doses large enough to cause convulsions stimulated the vasomotor

center. In smaller doses it generally stimulated the center

moderately, but not always. Even when this center was stimulated,

however, the camphor did not necessarily increase the blood

pressure. The rise in blood pressure from epinephrin is due entirely

to its action on the peripheral blood vessels and the heart. It has

no action on the vasomotor center. They found that strychnin in

large doses may stimulate the vasomotor center moderately, but

usually it did not act on this center unless the patient was

asphyxiated; then it acted intensely. The conclusion to be drawn

from their experiments is that when there is asphyxia, increased

venous pressure, and also a rising blood pressure from the

stimulation of carbon dioxid, strychnin is contraindicated.



It should be recognized that digitalis very frequently not only does

not raise blood pressure, but also may lower it; especially in

aortic insufficiency and when there is cyanosis. Even with some

forms of angina pectoris, digitalis in small doses may reduce the

frequency of the pain. This decrease of pain following the use of

digitalis has in some cases been ascribed to the improvement of

coronary circulation and resulting better nutrition of heart muscle.

Of course under these conditions the action of digitalis must be

carefully watched, and it should not be given too long.



Although sodium nitrite and nitroglycerin have but a short period of

action, in laboratory experimentation, in lowering the blood

pressure, when given repeatedly four or five times a day the blood

pressure is lowered in very many instances by these drugs. Sometimes

when the blood pressure is not lowered, there is relief of tension

in the head from high pressure, and the patient feels better. There

is also relief of the heart when it is laboring to overcome a high

resistance. One drop of the official spirit of nitroglycerin on the

tongue will cause a lowering in the peripheral pressure pulse, the

radial pulse becoming larger and fuller. This effect begins in three

minutes or less, reaches its maximum in about five minutes, and the

effect passes off in fifteen minutes or more. [Footnote: Hewlett, A.

W., and Zwaluwenburg, J. G. Van: The Pulse Flow in the Brachial

Artery, Arch. Int. Med., July, 1913, p. 1.]



It has been stated that iodids are of no value except in syphilitic

arteriosclerosis, but iodids in small doses are stimulant to the

thyroid gland, and the thyroid secretes a vasodilating substance.

Therefore, the use of either iodids or thyroid would seem to be

justified in many instances of high blood pressure.



Fairlee [Footnote: Fairlee: Lancet, London, Feb. 28, 1914.] has

studied the effect of chloroform and ether on blood pressure, and

finds that there is a fall of pressure throughout the administration

of chloroform, and but little alteration of the blood pressure

during the administration of ether. It may cause a slight rise, or

it may cause a slight fall, but changes in pressure with ether are

not marked. When there is slight surgical shock present, as from

some injury, they found that chloroform would lower the pressure

considerably. Hence it would seem that chloroform should not be used

as an anesthetic after serious injuries.





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