POINT TO NOTE ON BLOOD PRESSURE
BLOOD
Blood is the fluid that circulate through the heart and blood vessels, supplying oxygen and nutritive materials to all parts of the body and carrying off waste products. Physiology of the blood cells Blood is composed of the following parts:- Red blood cells with their haemaeglobin; White blood cells, and Tiny little bodies much smaller than the red cells, which are called platelets.
The blood also contains a clear yellow fluid, which is known as plasma. Plasma contains the following important substances:-
Certain substances: such as prothrombin and fibrinogen- which are important in the mechanism of blood clotting.
Various salts: such as calcium, sodium,sugar, protein, etc- all of which areessential for the proper nutrition of the body.
Certain waste products: such as urea- from the various organs in the body, and Certain substances known as antibodies, which play important roles in solving the problem of immunity and resistance against infection.
THE NORMAL BLOOD COUNT
The normal blood count in an adult is:-
Red blood cells = 5,000.00 per cubic millimeters (/mm3 ).
Haemoeglobin = 12-14.5gm per 100ml. of blood (usually expresses in percentage).
White blood cells = 5,000 to 10,000 per cubic millimeter (/mm3 ), and
Platelets + 200,000 per cubic millimeters (/mm3 ) approximately.
BLOOD PRESSURE
It is the pressure of force that the blood exerts against the walls of the bloodvessels.
Though there is some pressure in all blood vessels, the term is genrally used in reference to arterial blood pressure, which is measured in the brocjial artery by means of an instrument known and called SPHYGMOMANOMETER.
Two levels are recorded, viz:
A systolic pressure; which is the maximum pressure during contraction of the ventricles, and
A diastolic pressure; which is the pressure in the vessel when ventricles are at rest.
THE NORMAL BLOOD PRESSURE
In adults the normal Systolic Blood Pressure at rest varies on average from 110 to 150 mm of mercury.
The Diastolic Blood Pressure; which measure the blood pressure when the heart is resting, varies from 70 to 90mm of mercury.
The blood pressure is taken by a special instrument called a Sphygmomanometer, as earlier on stated.
CAUSES OF HYPERTENSION
A raised blood pressure may be caused by many different diseases e.g.
Chronic nephritis, which is the inflammation of the kidneys;
Toxaemias of pregnancy – i.e. poisoning of the blood by the absorption of toxins.
Tumors of adrenal gland;
Diminished blood supply to the kidneys (renal ischaemia), and
Excessive strain e.g. mental strain.
AFTER EFFECTS OF HYPERTENSION
The effects of the increased pressure in the arteries are numerous and in most cases serious. Some of the effects include, but not limited to the following:-The left ventricle of the heart enlarges and hypertrophies to counteract the extra pressure in the arteries. Eventually, if the strain becomes too severe the heart may not be able to cope and heart failure sets in. The walls of the renal arteries, owing to increased pressure, become thickened and narrow, which leads to a diminished blood supply to the kidneys. This causes, in turn, a loss of function and may lead to chronic renal failure. The raised pressure commonly causes rupture of certain arteries especially, the cerebral arteries. This results in cerebral haemorrhage (apoplexy or stroke). The continuos raised blood pressure often aggravates or predisposes to sclerotic changes in the arteries with the result that angina pectoris, coronary thrombosis are all frequently seen in associatin with hypertension.
SIGNS AND SYMPTOMS OF HYPERTENSION
Hypertension is often present for many years- perhaps ten or fifteen- during which it causes the few symptoms listed below. Headache, giddiness, ringing in the ears and epistaxis are commonest early symptoms. Eventually, however, owing to the persistently increased pressure against which the heart has to work, heart failure develops. In severe cases of hypertentsion, attacks known as hypertensive encephalopathy may arise. Severe cases of headache, vomiting, convulsions, and paralysis may arise.
TREATMENT OF A RAISED BLOOD PRESSURE
There is no specific cure of raised blood pressure. However, some precautions may assist a potential patient to lead an almost normal living.\ Some of the precautions include the following: As mental strain is an important factor, patients are advised to avoid, as much as possible, all worry and emotional upsets and to lead a relatively quiet life. Sedatives- such as phenobrabitones- are very useful to relieve quite life. If obesity is present, a reduction in weight is advisable and a low- calorie diet should be prescribed. Rest in a hospital is recommended.
Venessection of a pint of blood at periodic intervals is often useful in reducing a high blood pressure for a short period of time. Patients with the more sever grades of hypertension are treated with anti-hypertension drugs. Unforturnately, most of the available anti-hypertension drugs are very liable to cause severe side effects when given in doses large enough to be effective. New drugs are continually being introduced in an effort to provide effective hypotensive therapy with minimum side effects.
The hypotensive drugs most frequently used at presents include:
· Guanelnidine (Ismelin 10-20mg); once daily as a dose gradually increased until the blood pressure is controlled.
· Methyldopa (Aldomet) lowers the blood pressure by preventing the formation of Adrenalin. The effective dose varies from 0.5 to 4mg daily and is most useful for patients with moderate H.B.P.
The action of these hypotensive drugs are greatly enhanced when the oral diuretic chlorothiaside (saluric) or one of its derivatives is given at the same time- e.g. modurectic. During the initial period of stabilization on hypotensive drugs, care must be taken to increase thedose only gradually since the blood pressure may fall suddenly. If the patient is in the ward, the blood pressure must be recorded daily.
