Vasoconstrictors Health Dictionary

Vasoconstrictors: From 1 Different Sources


Vasoconstrictor sympathomimetic drugs, such as EPHEDRINE and NORADRENALINE, raise the BLOOD PRESSURE temporarily by acting on receptors that constrict peripheral blood vessels. They are occasionally used as a quick way of raising blood pressure when other measures have failed, but they have potentially serious side-effects on the kidney. Vasoconstrictors are also used with local anaesthetics (see under ANAESTHESIA) to counteract the latter’s vasodilator e?ect. Adrenaline will reduce local blood ?ow, slow the absorption of anaesthetic and prolong its e?ect.
Health Source: Medical Dictionary
Author: Health Dictionary

Rectum, Diseases Of

The following are described under their separate dictionary entries: FAECES; HAEMORRHOIDS; FISTULA; DIARRHOEA; CONSTIPATION.

Imperforate anus, or absence of the anus, may occur in newly born children, and the condition is relieved by operation.

Itching at the anal opening is common and can be troublesome. It may be due to slight abrasions, to piles, to the presence of threadworms (see ENTEROBIASIS), and/or to anal sex. The anal area should be bathed once or twice a day; clothing should be loose and smooth. Local application of soothing preparations containing mild astringents (bismuth subgallate, zinc oxide and hamamelis) and CORTICOSTEROIDS may provide symptomatic relief. Proprietary preparations contain lubricants, VASOCONSTRICTORS and mild ANTISEPTICS.

Pain on defaecation is commonly caused by a small ulcer or ?ssure, or by an engorged haemorrhoid (pile). Haemorrhoids may also cause an aching pain in the rectum. (See also PROCTALGIA.)

Abscess in the cellular tissue at the side of the rectum – known from its position as an ischio-rectal abscess – is fairly common and may produce a ?stula. Treatment is by ANTIBIOTICS and, if necessary, surgery to drain the abscess.

Prolapse or protrusion of the rectum is sometimes found in children, usually between the ages of six months and two years. This is generally a temporary disorder. Straining at defaecation by adults can cause the lining of the rectum to protrude outside the anus, resulting in discomfort, discharge and bleeding. Treatment of the underlying constipation is essential as well as local symptomatic measures (see above). Haemorrhoids sometimes prolapse. If a return to normal bowel habits with the production of soft faeces fails to restore the rectum to normal, surgery to remove the haemorrhoids may be necessary. If prolapse of the rectum recurs, despite a return to normal bowel habits, surgery may be required to rectify it.

Tumours of small size situated on the skin near the opening of the bowel, and consisting of nodules, tags of skin, or cauli?ower-like excrescences, are common, and may give rise to pain, itching and watery discharges. These are easily removed if necessary. Polypi (see POLYPUS) occasionally develop within the rectum, and may give rise to no pain, although they may cause frequent discharges of blood. Like polypi elsewhere, they may often be removed by a minor operation. (See also POLYPOSIS.)

Cancer of the rectum and colon is the commonest malignancy in the gastrointestinal tract: around 17,000 people a year die from these conditions in the United Kingdom. Rectal cancer is more common in men than in women; colonic cancer is more common in women. Rectal cancer is a disease of later life, seldom affecting young people, and its appearance is generally insidious. The tumour begins commonly in the mucous membrane, its structure resembling that of the glands with which the membrane is furnished, and it quickly in?ltrates the other coats of the intestine and then invades neighbouring organs. Secondary growths in most cases occur soon in the lymphatic glands within the abdomen and in the liver. The symptoms appear gradually and consist of diarrhoea, alternating with attacks of constipation, and, later on, discharges of blood or blood-stained ?uid from the bowels, together with weight loss and weakness. A growth can be well advanced before it causes much disturbance. Treatment is surgical and usually this consists of removal of the whole of the rectum and the distal two-thirds of the sigmoid colon, and the establishment of a COLOSTOMY. Depending upon the extent of the tumour, approximately 50 per cent of the patients who have this operation are alive and well after ?ve years. In some cases in which the growth occurs in the upper part of the rectum, it is now possible to remove the growth and preserve the anus so that the patient is saved the discomfort of having a colostomy. RADIOTHERAPY and CHEMOTHERAPY may also be necessary.... rectum, diseases of

Sympathomimetic

adj. having the effect of stimulating the *sympathetic nervous system. The actions of sympathomimetic drugs are adrenergic: they act on alpha or beta *adrenoceptors. Alpha-adrenergic stimulants (alpha agonists) stimulate alpha receptors. They include *vasoconstrictors (e.g. *ephedrine, *phenylephrine, *metaraminol), used to treat nasal congestion and severe hypotension, and the selective ?2 agonists *apraclonidine and *brimonidine, which are used in the treatment of glaucoma. Beta-adrenergic stimulants (beta agonists) stimulate ?1 and/or ?2 adrenoceptors. ?2 agonists such as *salbutamol, *salmeterol, and *terbutaline relax bronchial smooth muscle and are used as *bronchodilators. Some ?2 agonists, including salbutamol, relax uterine muscle and are sometimes used in the treatment of premature labour (see tocolytic). ?1 agonists (e.g. *dobutamine) stimulate ?1 receptors in the heart and are therefore used for their *inotropic effects.... sympathomimetic

Vasoconstrictor

n. an agent that causes narrowing of the blood vessels and therefore a decrease in blood flow. Vasoconstrictor drugs are alpha agonists (see sympathomimetic): they are used to raise the blood pressure in disorders of the circulation, shock, or severe bleeding and to maintain blood pressure during surgery (e.g. *ephedrine, *metaraminol, *phenylephrine). Some vasoconstrictors (e.g. ephedrine, *xylometazoline) have a rapid effect when applied to mucous membranes and may be used to relieve nasal congestion. If the blood pressure rises too quickly headache and vomiting may occur. A vasoconstrictor is often added to local anaesthetic solutions used in dentistry to prolong their effectiveness.... vasoconstrictor



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