Internal Medicine Informations

Internal Medicine Informations
Blood Pressure, pressure of circulating blood against the walls of the arteries. Blood pressure is an important diagnostic index, especially of circulatory function. Because the heart can pump into the large arteries a greater volume of blood than can be absorbed by the tiny arterioles and capillaries, the resulting back pressure is exerted against the arteries. Any condition that dilates or contracts the blood vessels or affects their elasticity, or any disease of the heart that interferes with its pumping power, affects the blood pressure. In a healthy animal, the blood pressure normal for its species is maintained within a certain average range with great constancy. Controlled by both cerebrospinal and sympathetic nerve centers, the complex nervous system mechanisms that balance and coordinate the activity of the heart and arterial muscles permit great local variation in the rate of blood flow without disturbing the general blood pressure.
In 1996 scientists discovered that hemoglobin, the iron-protein compound that gives blood its red color, also plays a role in regulating local variation in blood pressure. Hemoglobin was found to carry nitric oxide, a gas that relaxes the blood vessel walls, thus increasing blood flow. Hemoglobin controls the expansion and contraction of blood vessels, and thus blood pressure, by regulating the amount of nitric oxide to which the vessels are exposed.
Blood pressure is measured at two points: the high point at which the heart contracts to empty its blood into the circulation, called systole; and the low point at which the heart relaxes to fill with blood returned by the circulation, called diastole. Pressure is measured in millimeters (mm) of mercury by an instrument called a sphygmomanometer, consisting of an inflatable rubber cuff connected to a pressure-detecting device with a dial. The cuff is wrapped around the upper arm and inflated by squeezing a rubber bulb connected to it by a tube. Meanwhile, the health professional making the examination listens to a stethoscope applied to an artery in the lower arm. As the cuff expands, it gradually compresses the artery. The point at which the cuff stops the circulation and at which no pulsations can be heard is read as the systolic pressure. As the cuff is slowly deflated, a spurting sound can be heard when the heart contraction forces blood through the compressed artery. The cuff is then allowed gradually to deflate further until the blood is flowing smoothly again and no further spurting sound is heard. A reading at this point shows the diastolic pressure that occurs during relaxation of the heart. During a single cardiac cycle, or heartbeat, the blood pressure reaches maximum during systole and minimum during diastole. Usually, both measurements are given as a ratio expression of maximum over minimum—for example, 140/80. When a single figure is given, it is usually the higher, or systolic, pressure.
In healthy persons, blood pressure increases from about 80/45 in infants, to about 120/80 at age 30, to about 140/85 at age 40 and over. This increase occurs when the arteries lose the elasticity that, in younger people, absorbs the force of heart contractions. Blood pressure is influenced by a wide range of factors and varies between individuals and in the same individual at different times. It is generally higher in men than in women and children and is lowest during sleep.
Abnormally high blood pressure, or hypertension, is considered a contributory cause of arteriosclerosis. Poisons generated within the body cause extreme hypertension in various disorders. Abnormally low blood pressure, or hypotension, is observed in infectious and wasting diseases, hemorrhage, and collapse. Many healthy persons, however, have habitual systolic pressures of from about 95 to 115 that are not associated with symptoms or disease. A systolic pressure of much lower than 80 is usually associated with shock.

Hypertension or High Blood Pressure, physiological condition involving increased pressure on the arterial walls (see Blood Pressure). Generally both the systolic and diastolic pressure are elevated, although diastolic pressure only may be increased (see Heart: Structure and Function). Many persons have a condition known as labile hypertension, in which blood pressure is elevated on initial examination but registers normal on subsequent measurements. For this reason a diagnosis of true, or sustained, hypertension requires elevated blood pressure readings on several occasions.
Elevated arterial blood pressure indicates increased arterial resistance to blood flow (see Artery), but in 90 percent of patients no cause for this increased resistance can be identified. These cases are called primary, or essential, hypertension. Secondary hypertension can be the outcome of toxemia, of pregnancy, vascular or kidney diseases, or endocrine tumors. See Endocrine System: Disturbances of Endocrine Function; Kidney: Diseases of the Kidney.

Classificatio of B.P:--

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Classification of blood pressure levels for adults 18 years and older. Systolic pressure, the higher number of a blood pressure reading, is the pressure as the heart pumps; diastolic pressure is the pressure when the heart relaxes between beats.
CATEGORY			SYSTOLIC (mm Hg†)	DIASTOLIC (mm Hg†)
Normal*			< 130	< 85
High normal			130-139	85-89
Hypertension
STAGE 1 (Mild)			140-159	90-99
STAGE 2 (Moderate)			160-179	100-109
STAGE 3 (Severe)			180-209	110-119
STAGE 4 (Very Severe)			>209	>119
†	Measured in millimeters of mercury.
*	Optimal blood pressure is less than 120/80 mm Hg. Unusually low readings should be evaluated by a physician.
Source:		Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure; National Institutes of Health.

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Detection
The average age of onset of essential hypertension is about 35. Some degree of hypertension is present in about one in six American adults and is more common in blacks than in whites. Most persons with hypertension have no symptoms. For this reason large-scale screening programs have been instituted to detect people with elevated blood pressure, for if left untreated, hypertension increases the risk of death from heart attack (see Heart: Heart Diseases) and produces damage to the kidneys, nervous system, and especially the eyes. When found early and treated, the effects of this condition can be greatly reduced. Blood pressure can vary greatly with circumstances or time of day, or with patient's age, so undue significance should not be placed upon a single reading.
Treatment
Several types of drugs have proved useful for severe hypertension. Diuretics (see Diuretic) promote salt and water excretion, reducing the work the heart must do to pump blood through the kidneys; vasodilators, renin inhibitors, and calcium antagonists reduce the resistance to blood flow in arteries; and ganglionic blockers and beta-adrenergic blockers help to control heartbeat and arterial tone. Therapy also includes a low-salt diet and an attempt to reduce the emotional stress of the patient's life. Drug treatment for mild hypertension is debated, because the drugs can have side effects that exceed their usefulness.
The widespread detection and treatment of hypertension in Western countries has been credited with contributing to the dramatic fall in death from heart disease that occurred during the 1970s and '80s.

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