The Effect Of Drugs On Blood Pressure
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 systo
ic 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.