Venous Pressure


Categories: Uncategorized
Sources: Disturbances Of The Heart

The venous pressure, after a long neglect, is now again being

studied, and its determination is urged as of diagnostic and

prognostic significance.



Hooker [Footnote: Hooker: Am. Jour. Physiol., March, 1916.] says

there is a progressive rise of venous pressure from youth to old

age. He has described an apparatus [Footnote: Hooker: Am. Jour.

Physiol., 1914, xxxv, 73.] which allows of the reading of the blood

pressure in a vein of the hand when the arm is at absolute rest, and

best with the patient in bed and reclining at an angle of 45

degrees. He finds that just before death there is a rapid rise in

venous pressure, or a continuously high pressure above the 20 cm. of

water level, and he believes that a venous pressure continuously

above this 20 cm. of water limit which is not lowered by digitalis

or other means is serious; and that the heart cannot long stand such

a condition. These dangerous rises in venous pressure are generally

coincident with a fall of systolic arterial pressure, although there

may be no constant relation between the two. He also finds that with

an increase of venous pressure the urinary output decreases. This,

of course, shows venous stasis in the kidneys as well as a probable

lowering of arterial pressure.



Clark [Footnote: Clark, A. D.: A Study of the Diagnostic and

Prognostic Significance of Venous Pressure Observations in Cardiac

Disease, Arch. Int. Med., October, 1915, p. 587.] did not find that

venesection prevented a subsequent rapid rise in venous pressure in

dire cases. From his investigations he concludes that a venous

pressure of 20 cm. of water is a danger limit between compensation

and decompensation of the heart, and a rise above this point will

precede the clinical signs of decompensation.



Hooker also found that there are daily variations of venous pressure

from 10 to 20 cm. of water, with an average of 15 cm., while in

sleep it falls 7 or 8 cm.



It seems probable that there may be a special nervous mechanism of

the veins which may increase the blood pressure in them as

epinephrin solution may cause some constriction.



Wiggers [Footnote: Wiggers C. J.: The Supravascular Venous Pulse in

Man, THE JOURNAL. A.M.A., May 1, 1915, p. 1485.] describes a method

of taking and interpreting the supraclavicular venous pulse. He also

[Footnote: Wiggers C. J.: The Contour of the Normal Arterial Pulse,

THE JOURNAL. A.M.A., April 24, 1915, p. 1380.] carefully describes

the readings and the different phases of normal arterial pulse, and

urges that it should be remembered that "the pulse as palpated or

recorded from any artery is the variation in the arterial volume

produced by the intra-arterial pressure change at that point."



A quick method of estimating the venous pressure by lowering and

raising the arm has long been utilized. The dilatation of the veins

of the back of the hand when the hand is raised should disappear,

and they should practically collapse, in normal conditions, when the

hand is at the level of the apex of the heart. When the venous

pressure is increased, this collapse will not occur until the hand

is above the level of the heart. Oliver [Footnote: Oliver: Quart.

Med Jour., 1907, i, 59.] found that the venous pressure denoted by

the collapse of the veins may be shown approximately in millimeters

of mercury by multiplying by 2 each inch above the level of the

heart in which the veins collapse. When a normal person reclines

after standing there is a fall in venous pressure, and when he again

stands erect there is an increase in venous pressure.



Bailey [Footnote: Bailey: Am. Jour Med. Sc., May, 1911, p. 709.]

states that in interpreting pulsation in the peripheral veins, it

should not be forgotten that they may overlie pulsating arteries.

Pulsation in veins may be due also to an aneurysmal dilatation, or

to direct connection with an artery. As the etiology in many

instances of varicose veins is uncertain, he thinks that they may be

caused by incompetence of the right heart, more or less temporary

perhaps, from muscular exertion. This incompetence being frequently

repeated, peripheral veins may dilate. Moreover, the contraction of

the right heart may cause a wave in the veins of the extremities,

and he believes that incompetency of the tricuspid valve may be the

cause of varicosities in the veins of the extremities.





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