In most people, high blood pressure causes no symptoms, despite the coincidental occurrence of certain symptoms that are widely, but erroneously, attributed to high blood pressure: headaches, nosebleeds, dizziness, a flushed face, and fatigue. People with high blood pressure may have these symptoms, but the symptoms occur just as frequently in people with normal blood pressure.
关于诊断:
Diagnosis
Blood pressure is measured after a person sits or lies down for 5 minutes. It should be measured again after the person stands for a few minutes, especially if the person is older or has diabetes. A reading of 140/90 mm Hg or more is considered high, but a diagnosis cannot be based on a single high reading. Sometimes, even several high readings are not enough to make the diagnosis—because, for example, the readings may vary too much. If a person has an initial high reading, blood pressure is measured again during the same visit and then measured twice on at least two other days to make sure that the high blood pressure persists.
Classifying Blood Pressure in Adults
Blood pressure is classified by its severity because treatment is based, in part, on severity. When a person’s systolic and diastolic pressures fall into different categories, the higher category is used to classify blood pressure. For instance, 150/88 mm Hg is classified as stage 1 hypertension, and 150/105 mm Hg is classified as stage 2 hypertension.
The optimal blood pressure for minimizing the risk of cardiovascular problems (such as heart attack and heart failure) and stroke is below 115/75 mm Hg.
Category
Systolic Blood Pressure (mm Hg)
Diastolic Blood Pressure (mm Hg)
Recommended Follow-up
Normal blood pressure
Below 120
Below 80
Blood pressure is rechecked in 2 years.
Prehypertension
120–139
80–89
Blood pressure is rechecked in 1 year, and advice about lifestyle changes is provided.
Stage 1 hypertension
140–159
90–99
The high blood pressure is confirmed within 2 months, and advice about lifestyle changes is provided.
Stage 2 hypertension
Above 160
Above 100
The person is evaluated or referred to a health care provider within 1 month. For people with very high pressures (such as 180/110 mm Hg or higher), evaluation or treatment is immediate or within 1 week, depending on the person’s condition.
关于血压的调节机制:
Regulating Blood Pressure: The Renin-Angiotensin-Aldosterone System
The renin-angiotensin-aldosterone system is a series of reactions designed to help regulate blood pressure.
When blood pressure falls (for systolic, to 100 mm Hg or lower), the kidneys release the enzyme renin into the bloodstream.
Renin splits angiotensinogen, a large protein that circulates in the bloodstream, into pieces. One piece is angiotensin I.
Angiotensin I, which is relatively inactive, is split into pieces by angiotensin-converting enzyme (ACE). One piece is angiotensin II, a hormone, which is very active.
Angiotensin II causes the muscular walls of small arteries (arterioles) to constrict, increasing blood pressure. Angiotensin II also triggers the release of the hormone aldosterone from the adrenal glands and antidiuretic hormone from the pituitary gland.
Aldosterone and antidiuretic hormone cause the kidneys to retain salt (sodium). Aldosterone also causes the kidneys to excrete potassium. The increased sodium causes water to be retained, thus increasing blood volume and blood pressure.