View report page

BLOOD PRESSURE
Hypertension.
In normal healthy persons the blood is held at a pressure of about 70
millimetres of mercury; every beat of the heart forces a quantity of blood into
the arterial system and the pressure is raised to about 120 millimetres of
mercury for a fraction of a second, and then it drops again to 70 until the next
heart beat starts the cycle again. When a patient suffers as we say from
"blood pressure" we mean that the ordinary normal blood pressure is habitually
higher than it should be, and that there is a threat to the health or life of the
patient. The blood pressure rises in times of stress or excitement and will
subside naturally to normal limits when the stress or excitement ceases. In
acute infection of the kidney, or in the affection of the kidney due to abnormal
poisons in pregnancy, the blood pressure can be raised, sometimes quite
dangerously, but the pressure returns to normal when the infection is healed
or the pregnancy ended. Other forms of disease of the kidney or the adrenal
gland near the kidney can produce high blood pressure; if the affection is
confined to one site, and if it is possible to remove the cause, there is sometimes
resumption of the normal blood pressure.
The Dangerous Level.
However, there are some cases of high blood pressure whose cause is not
exactly known; the blood pressure in these persons continues to rise and to
remain at a high level in what appears to be the absence of any obvious disease.
Indeed, the blood pressure can go on rising until it gets to such a level that the
nerves in the retina at the back of the eye become affected and both sight and
life are in danger. Raised blood pressure which is not excessive is known as
benign hypertension, but the type which approaches dangerous level is known
as malignant hypertension. In the absence of known cause the two together
are designated essential hypertension. The threat to life is from stroke—a
vessel bursting in the brain.
Most doctors distinguish two types of raised blood pressure, that due to
diseases of the kidneys known as renal hypertension, and that due to other but
unknown causes known as essential hypertension. However, whether the
causes of the raised blood pressure is due to kidney disease or to some unknown
cause, the very presence of the high blood pressure itself has an effect on the
kidneys, which degenerate and become diseased and make the blood pressure
rise higher still.
If it is possible to lower the blood pressure in some way, it is possible to
avert the dangerous phase of malignant hypertension and to save life and
eyesight. The reduction of blood pressure can be effected by operation, or
by drugs. There are very marked differences in individuals; women can
sustain a level of high blood pressure which in men would in a few years turn
to the malignant type with dire consequences.
11