Hypertension, commonly referred to as "high blood pressure" or HTN, is a medical condition in which ones blood pressure is chronically elevated and is classified as either essential (primary) or secondary. Essential hypertension describes high blood pressure not attributable to a known specific medical cause, but is present nonetheless. Secondary hypertension is high blood pressure attributable to (i.e. secondary to) another known condition, such as kidney disease or certain tumors (especially of the adrenal gland). Chronic hypertension is a risk factor for strokes, heart attacks, heart failure and arterial aneurysm, and is one of the leading causes of chronic kidney failure. Chronic elevation of arterial blood pressure decreases life expectancy. Severely elevated blood can reduce ones life expectancy to a few years unless treated appropriately.
High blood pressure (Hypertension) is defined when a person's systolic (upper blood pressure reading) is consistently 140 mmHg or greater, and/or their diastolic blood pressure (lower blood pressure reading) is routinely 90 mmHg or greater. As of 2003, the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure has defined blood pressure 120/80 mmHg to 139/89 mmHg as "prehypertension." Prehypertension is not a specific disease category; rather, it designates individuals at high risk of developing full-blown hypertension. In patients with diabetes mellitus or kidney disease studies have shown that blood pressure readings over 130/80 mmHg should be considered high and therefore, warrant treatment.
Salt Sensitivity
Sodium has received a great deal of attention. Approximately 60% of essential hypertension responds due to reduced sodium intake. This maybe because of increased osmolality caused in a person's bloodstream by increased sodium in the blood that causes the body to draw more water into the blood stream; thereby, increasing the pressure in the blood vessels and on the blood vessel walls. Also, chloride (the other molecule generally combined with sodium) in the modern processed food diet can act on the kidney to retain fluid, and thereby increase blood pressure.
The effects of excess amounts of salt--a compound containing both minerals, sodium and chloride depend on how much excess salt (or salty foods) is eaten in a specific time versus how well the kidneys function. When the salt content of the blood is increased, water is attracted from around the cells and into the blood, in order to dilute the high osmolality of blood caused by the salt. When the salt content of the fluid around cells goes up, it attracts water from the blood and swelling occurs. When your kidneys don't work well, fluid is not removed from the blood and builds up around cells and in your blood vessels. If there is more fluid in your blood this can cause your blood pressure to go up because there is more pressure on the walls of your blood vessels. Salt has been blamed for causing high blood pressure, but too little calcium, magnesium or potassium also has an impact on blood pressure.
Causes of secondary hypertension
Only a small minority of patients with hypertension have an identifiable cause. These individuals are likely to have an endocrine or kidney defect that, if corrected, could reduce blood pressure to normal values.
Renal hypertension
High blood pressure produced by diseases of the kidney. This includes diseases such as polycystic kidney disease or chronic glomerulonephritis. Diseases of the renal arteries supplying the kidney can also produce hypertension. This is known as renovascular hypertension; it is thought that decreased perfusion of renal tissue due to stenosis of a main or branch renal artery activates the renin-angiotensin system.
Adrenal hypertension
High blood pressure is a feature of a variety of adrenal cortical abnormalities. In primary aldosteronism there is a clear relationship between the aldosterone-induced sodium retention and the hypertension.
Cushing's syndrome (hypersecretion of cortisol)
Both adrenal glands can overproduce the hormone cortisol or it can arise in a benign or malignant tumor. High blood pressure results from the interplay of several mechanisms regulating plasma volume, peripheral vascular resistance and cardiac output, all of which may be increased. More than 80 percent of patients with Cushing's syndrome have high blood pressure.
In patients with pheochromocytoma increased secretion of catecholamines such as epinephrine and norepinephrine by a tumor (most often located in the adrenal medulla) causes excessive stimulation of adrenergic receptors, which results in peripheral vasoconstriction and cardiac stimulation. This diagnosis is confirmed by demonstrating increased urinary excretion of epinephrine and norepinephrine and/or their metabolites (vanillylmandelic acid).
Age
Over time, the number of collagen fibers in artery and arteriole walls increases, making blood vessels stiffer. With reduced elasticity a smaller cross-sectional area develops during systole, and this results in raised mean arterial blood pressure.
Signs and symptoms
Hypertension is usually found incidentally by healthcare professionals during a routine checkup. The only test for high blood pressure is a blood pressure measurement. Hypertension in isolation usually produces no symptoms although some people my report headaches, fatigue, dizziness, blurred vision, facial flushing or tinnitus.
Malignant hypertension may present with headaches, blurred vision and end-organ damage.
Hypertensive urgencies and emergenciesHigh blood pressure is rarely severe enough to cause symptoms. These typically only surface only when systolic blood pressure is over 240 mmHg and/or a diastolic blood pressure over 120 mmHg. When end-organ damage is possible or already ongoing it is called hypertensive emergency. Hypertension under this circumstance needs to be controlled, but prolonged hospitalization is not necessarily required. When hypertension causes increased intracranial pressure, it is called malignant hypertension. Increased intracranial pressure causes papilledema, which is visible on ophthalmoscopic examination of the retina.
Complications
While elevated blood pressure alone is not an illness, it often requires treatment due to its short- and long-term effects on many organs. When damage is done to organs and tissues we call these conditions:
Cerebrovascular accident (CVAs or strokes)
Hypertension of pregnancy
Although few women of childbearing age have high blood pressure, up to 10% develop hypertension during pregnancy. Although usually benign, it may herald three complications of pregnancy: pre-eclampsia, HELLP syndrome and eclampsia. Follow-up and control with medication is therefore often necessary.
Measuring blood pressure
Diagnosis of hypertension is generally on the basis of a persistently high blood pressure. Usually this requires three separate measurements at least one week apart. If the elevation is extreme, or end-organ damage is present then the diagnosis may be applied and treatment commenced immediately.
Obtaining reliable blood pressure measurements relies on following several rules and understanding the many factors that influence blood pressure reading.
For instance, measurements in control of hypertension should be at least 1 hour after caffeine, 30 minutes after smoking and without any stress. Cuff size is also important. The blood pressure cuff should encircle and cover two-thirds of the length of the arm. The patient should be sitting for a minimum of five minutes. The patient should not be on any stimulants, such as those found in many cold medications.
When taking manual measurements, the person taking the measurement should be mindful to inflate the cuff suitably above the systolic pressure. The cuff should be at the level of the heart. Two measurements should be made at least 5 minutes apart, and, if there is a discrepancy of more than 5 mmHg, a third reading should be done. The readings should then be averaged.
BP varies with time of day, and as such reading should be taken initially at different times of the day.
Routine measurements done in medical offices or facilities may incorrectly diagnose hypertension because of what is known as the "White Coat Effect".
Home blood pressure monitoring can provide a measurement of a person's blood pressure at different times throughout the day and in different environments, such as at home and at work. Home monitoring may assist in the diagnosis of high or low blood pressure. It may also be used to monitor the effects of medication or lifestyle changes taken to lower or regulate blood pressure levels.
Home monitoring of blood pressure can also assist in the diagnosis of white coat hypertension. The American Heart Association states, "You may have what's called 'white coat hypertension'; that means your blood pressure goes up when you're at the doctor's office. Monitoring at home will help you measure your true blood pressure and can provide your doctor with a log of blood pressure measurements over time. This is helpful in diagnosing and preventing potential health problems."
Distinguishing primary vs. secondary hypertension
Once the diagnosis of hypertension has been made it is important to attempt to exclude or identify reversible (secondary) causes.
Over 91% of adult hypertension has no clear cause and is therefore called essential or primary hypertension. Secondary hypertension is more common in preadolescent children, with most cases caused by renal disease. Primary or essential hypertension is more common in adolescents and has multiple risk factors, including obesity and a family history of hypertension.
If you measure or suspect that you have high blood pressure you should visit your physician or certified health agency to be evaluated.
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