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.
Potassium 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.
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.
In the apparatus shown in the figure (Fig. 33), Drs. Hooker and Eyster succeeded in making estimations of the venous pressure. The box B is held in position by the tapes A, so that the vein is visible through the rectangular opening in the thin rubber covering the bottom. The box is connected with the water manometer G, by a rubber tube, from which a T-tube enters the rubber bulb E. When the bulb E is compressed between the plates D, by the coarse thumbscrew C, air is forced into the box B, exerting a pressure on the vein lying exposed beneath. This pressure is transmitted directly to the manometer G, and may be read off in centimeters of water on the accompanying scale. The veins of the back of the hand are used and there must be no obstruction between them and the heart. The rubber-covered box is accurately and lightly fitted over a vein and pressure made until it is obliterated. By measuring the distance above or below the heart level that the hand was when the observation was made, and subtracting or adding these figures to the manometer reading, we obtain the venous pressure at the heart level.
Eyster has modified this instrument so that it is now much simpler to operate. He uses a small glass cup with a flaring edge and a diameter of about 2 cm. This is sealed to the skin directly over a vein on the back of the hand by means of collodion. The stem of the cup has a rubber tube leading to a small hand bulb and to the manometer tube which contains colored water. Slight compression of the hand bulb obliterates the vein which can be seen through the glass cup. The pressure in centimeters of water is then read off. (Fig. 34.) The principle is the same as in the earlier instrument, but the application is easier.