The exact trigger is unknown, but it is thought that, whatever the stimulus, chemical mediators produced by cells of the immune system or elsewhere in the body spread and sustain an in?ammatory reaction. Cascade mechanisms with multiple interactions are provoked. CYTOTOXIC substances (which damage or kill cells) such as oxygen-free radicals and PROTEASE damage the alveolar capillary membranes (see ALVEOLUS). Once this happens, protein-rich ?uid leaks into the alveoli and interstitial spaces. SURFACTANT is also lost. This impairs the exchange of oxygen and carbon dioxide in the lungs and gives rise to the clinical and pathological picture of acute respiratory failure.
The typical patient with ARDS has rapidly worsening hypoxaemia (lack of oxygen in the blood), often requiring mechanical ventilation. There are all the signs of respiratory failure (see TACHYPNOEA; TACHYCARDIA; CYANOSIS), although the chest may be clear apart from a few crackles. Radiographs show bilateral, patchy, peripheral shadowing. Blood gases will show a low PaO2 (concentration of oxygen in arterial blood) and usually a high PaCO2 (concentration of carbon dioxide in arterial blood). The lungs are ‘sti?’ – they are less e?ective because of the loss of surfactant and the PULMONARY OEDEMA.
Causes The causes of ARDS may be broadly divided into the following:... Medical Dictionary
... Indian Medicinal Plants
PLEURISY with e?usion is a condition requiring aspiration, and a litre or more of ?uid may be drawn o? by an aspirator or a large syringe and needle. Chronic abscesses and tuberculous joints may call for its use, the operation being done with a small syringe and hollow needle. PERICARDITIS with e?usion is another condition in which aspiration is sometimes performed. The spinal canal is aspirated by the operation of LUMBAR PUNCTURE. In children the ventricles of the brain are sometimes similarly relieved from excess of ?uid by piercing the fontanelle (soft spot) on the infant’s head. (See HYDROCEPHALUS.)... Medical Dictionary
(e.g. cane sugar), polysaccharides (e.g. starch). Many of the cheaper and most important foods are included in this group, which comprises sugars, starches, celluloses and gums. When one of these foods is digested, it is converted into a simple kind of sugar and absorbed in this form. Excess carbohydrates, not immediately needed by the body, are stored as glycogen in the liver and muscles. In DIABETES MELLITUS, the most marked feature consists of an inability on the part of the tissues to assimilate and utilise the carbohydrate material. Each gram of carbohydrate is capable of furnishing slightly over 4 Calories of energy. (See CALORIE; DIET.)... Medical Dictionary
The main output of the Cochrane Collaboration is published electronically as the Cochrane Library, updated quarterly, with free access in many countries. (See CLINICAL TRIALS, EVIDENCE-BASED MEDICINE and Appendix 2.)... Medical Dictionary
11.8. The total mortality comprises individual deaths from di?erent causes: for example, accidents, cancer, coronary artery disease, strokes and suicides. Mortality is often calculated for speci?c groups in epidemiological (see EPIDEMIOLOGY) studies of particular diseases. Infant mortality measures the deaths of babies born alive who die during the ?rst year of life: infant deaths per 1,000 live births were steady at around 5 from 2003–2005.... Medical Dictionary
Causes of degeneration are, in many cases, very obscure. In some cases heredity plays a part, with particular organs – for example, the kidneys – tending to show ?broid changes in successive generations. Fatty, ?broid, and calcareous degenerations are part of the natural change in old age; defective nutrition may bring them on prematurely, as may excessive and long-continued strain upon an organ like the heart. Various poisons, such as alcohol, play a special part in producing the changes, and so do the poisons produced by various diseases, particularly SYPHILIS and TUBERCULOSIS.... Medical Dictionary
The start of ‘dehydration’ is signalled by a person becoming thirsty. In normal circumstances, the drinking of water will relieve thirst and serious dehydration does not develop. In a temperate climate an adult will lose 1.5 litres or more a day from sweating, urine excretion and loss of ?uid through the lungs. In a hot climate the loss is much higher – up to 10 litres if a person is doing hard physical work. Even in a temperate climate, severe dehydration will occur if a person does not drink for two or three days. Large losses of ?uid occur with certain illnesses – for example, profuse diarrhoea; POLYURIA in diabetes or kidney failure (see KIDNEYS, DISEASES OF); and serious blood loss from, say, injury or a badly bleeding ULCER in the gastrointestinal tract. Severe thirst, dry lips and tongue, TACHYCARDIA, fast breathing, lightheadedness and confusion are indicative of serious dehydration; the individual can lapse into COMA and eventually die if untreated. Dehydration also results in a reduction in output of urine, which becomes dark and concentrated.
Prevention is important, especially in hot climates, where it is essential to drink water even if one is not thirsty. Replacement of salts is also vital, and a diet containing half a teaspoon of table salt to every litre of water drunk is advisable. If someone, particularly a child, suffers from persistent vomiting and diarrhoea, rehydration therapy is required and a salt-andglucose rehydration mixture (obtainable from pharmacists) should be taken. For those with severe dehydration, oral ?uids will be insu?cient and the a?ected person needs intravenous ?uids and, sometimes, admission to hospital, where ?uid intake and output can be monitored and rehydration measures safely controlled.... Medical Dictionary
c.460 to 377 BC and who taught students at the medical school in Cos. Often called the ‘father of medicine’, he is renowned for drawing up the HIPPOCRATIC OATH, some of which may have been derived from the ancient oath of the Aesclepiads. Apart from his oath, Hippocrates has about 60 other medical works attributed to him, forming a corpus which was collected around 250 BC in the famous library of Alexandria in Egypt. Hippocratic medicine appealed ‘to reason rather than to rules or to supernatural forces’ is how the late Roy Porter, the English social historian, summed up its ethos in his medical history, The Greatest Bene?t to Mankind (Harper Collins, 1997). Porter also commended Hippocrates as being patient-centred rather than disease-orientated in his practice of medicine.... Medical Dictionary
The improvement in the infant mortality rate has occurred mainly in the period from the second month of life. There has been much less improvement in the neonatal mortality rate – that is, the number of infants dying during the ?rst four weeks of life, expressed as a proportion of every 1,000 live births. During the ?rst week of life the main causes of death are asphyxia, prematurity, birth injuries and congenital abnormalities. After the ?rst week the main cause of death is infection.
Social conditions also play an important role in infant mortality. In England and Wales the infant mortality rate in 1930–32 was: Social Class I (professional), 32·7; Social Class III (skilled workers), 57·6; Social Class V (unskilled workers), 77·1. Many factors come into play in producing these social variations, but overcrowding is undoubtedly one of the most important.
1838–9 146 1950–52 30 1851–60 154 1960–62 22 1900–02 142 1970–72 18 1910–12 110 1980–82 12 1920–22 82 1990–92 7 1930–32 67 1996 6·2 1940–42 59 1999 5.8 2000 5.6
It is thus evident that for a reduction of the infant mortality rate to the minimum ?gure, the following conditions must be met. Mothers and potential mothers must be housed adequately in healthy surroundings, particularly with regard to safe water supplies and sewage disposal. The pregnant and nursing mother must be ensured an adequate diet. E?ective antenatal supervision must be available to every mother, as well as skilled supervision during labour (see PREGNANCY AND LABOUR). The newborn infant must be adequately nursed and fed and mothers encouraged to breast feed. Environmental and public-health measures must be taken to ensure adequate housing, a clean milk supply and full availability of medical care including such protective measures as IMMUNISATION against diphtheria, measles, poliomyelitis and whooping-cough. (See also PERINATAL MORTALITY.)... Medical Dictionary
In developed countries ORT is useful in treating gastroenteritis. There are a number of proprietary preparations, often dispensed as ?avoured sachets, including Dioralyte® and Rehydrate®.... Medical Dictionary
The most common cause of this condition (hypoparathyroidism) is accidental injury to or removal of the glands during the operation of thyroidectomy for the treatment of Graves’ disease (see THYROID GLAND, DISEASES OF – Thyrotoxicosis). If there is over-production of the parathyroids, there will be an increase of calcium in the blood: this extra calcium is drawn from the bones, causing cysts to form with resulting bone fragility. This cystic disease of bone is known as OSTEITIS FIBROSA CYSTICA. Tumours of the parathyroid glands result in this overactivity of the parathyroid hormone, and the resulting increase in the amount of calcium in the blood leads to the formation of stones in the kidneys. The only available treatment is surgical removal of the tumour. Increased activity of the parathyroid glands, or hyperparathyroidism, may cause stones in the kidneys. (See KIDNEYS, DISEASES OF.)... Medical Dictionary
The chief object of perspiration is to maintain an even body temperature by regulating the heat lost from the body surface. Sweating is therefore increased by internally produced heat, such as muscular activity, or external heat. It is controlled by two types of nerves: vasomotor, which regulate the local blood ?ow, and secretory (part of the sympathetic nervous system) which directly in?uence secretion.
Eccrine sweat is a faintly acid, watery ?uid containing less than 2 per cent of solids. The eccrine sweat-glands in humans are situated in greatest numbers on the soles of the feet and palms of the hands, and with a magnifying glass their minute openings or pores can be seen in rows occupying the summit of each ridge in the skin. Perspiration is most abundant in these regions, although it also occurs all over the body.
Apocrine sweat-glands These start functioning at puberty and are found in the armpits, the eyelids, around the anus in association with the external genitalia, and in the areola and nipple of the breast. (The glands that produce wax in the ear are modi?ed apocrine glands.) The ?ow of apocrine sweat is evoked by emotional stimuli such as fear, anger, or sexual excitement.
Abnormalities of perspiration Decreased sweating may occur in the early stages of fever, in diabetes, and in some forms of glomerulonephritis (see KIDNEYS, DISEASES OF). Some people are unable to sweat copiously, and are prone to HEAT STROKE. EXCESSIVE SWEATING, OR HYPERIDROSIS, may be caused by fever, hyperthyroidism (see THYROID GLAND, DISEASES OF), obesity, diabetes mellitus, or an anxiety state. O?ensive perspiration, or bromidrosis, commonly occurs on the hands and feet or in the armpits, and is due to bacterial decomposition of skin secretions. A few people, however, sweat over their whole body surface. For most of those a?ected, it is the palmar and/or axillary hyperhidrosis that is the major problem.
Conventional treatment is with an ANTICHOLINERGIC drug. This blocks the action of ACETYLCHOLINE (a neurotransmitter secreted by nerve-cell endings) which relaxes some involuntary muscles and tightens others, controlling the action of sweat-glands. But patients often stop treatment because they get an uncomfortably dry mouth. Aluminium chloride hexahydrate is a topical treatment, but this can cause skin irritation and soreness. Such antiperspirants may help patients with moderate hyperhidrosis, but those severely a?ected may need either surgery or injections of BOTULINUM TOXIN to destroy the relevant sympathetic nerves to the zones of excessive sweating.... Medical Dictionary
Mechanism of respiration For the structure of the respiratory apparatus, see AIR PASSAGES; CHEST; LUNGS. The air passes rhythmically into and out of the air passages, and mixes with the air already in the lungs, these two movements being known as inspiration and expiration. INSPIRATION is due to a muscular e?ort which enlarges the chest, so that the lungs have to expand in order to ?ll up the vacuum that would otherwise be left, the air entering these organs by the air passages. The increase of the chest in size from above downwards is mainly due to the diaphragm, the muscular ?bres of which contract and reduce its domed shape and cause it to descend, pushing down the abdominal organs beneath it. EXPIRATION is an elastic recoil, the diaphragm rising and the ribs sinking into the position that they naturally occupy, when muscular contraction is ?nished. Occasionally, forced expiration may occur, involving powerful muscles of the abdomen and thorax; this is typically seen in forcible coughing.
Nervous control Respiration is usually either an automatic or a REFLEX ACTION, each expiration sending up sensory impulses to the CENTRAL NERVOUS SYSTEM, from which impulses are sent down various other nerves to the muscles that produce inspiration. Several centres govern the rate and force of the breathing, although all are presided over by a chief respiratory centre in the medulla oblongata (see under BRAIN – Divisions). This in turn is controlled by the higher centres in the cerebral hemispheres, so that breathing can be voluntarily stopped or quickened.
Quantity of air The lungs do not completely empty themselves at each expiration and re?ll at each inspiration. With each breath, less than one-tenth of the total air in the lungs passes out and is replaced by the same quantity of fresh air, which mixes with the stale air in the lungs. This renewal, which in quiet breathing amounts to about 500 millilitres, is known as the tidal air. By a special inspiratory e?ort, an individual can draw in about 3,000 millilitres, this amount being known as complemental air. By a special expiratory e?ort, too, after an ordinary breath one can expel much more than the tidal air from the lungs – this extra amount being known as the supplemental or reserve air, and amounting to about 1,300 millilitres. If an individual takes as deep an inspiration as possible and then makes a forced expiration, the amount expired is known as the vital capacity, and amounts to around 4,000 millilitres in a healthy adult male of average size. Figures for women are about 25 per cent lower. The vital capacity varies with size, sex, age and ethnic origin.
Over and above the vital capacity, the lungs contain air which cannot be expelled; this is known as residual air, and amounts to another 1,500 millilitres.
Tests of respiratory e?ciency are used to assess lung function in health and disease. Pulmonary-function tests, as they are known, include spirometry (see SPIROMETER), PEAK FLOW METER (which measures the rate at which a person can expel air from the lungs, thus testing vital capacity and the extent of BRONCHOSPASM), and measurements of the concentration of oxygen and carbon dioxide in the blood. (See also LUNG VOLUMES.)
Abnormal forms of respiration Apart from mere changes in rate and force, respiration is modi?ed in several ways, either involuntarily or voluntarily. SNORING, or stertorous breathing, is due to a ?accid state of the soft palate causing it to vibrate as the air passes into the throat, or simply to sleeping with the mouth open, which has a similar e?ect. COUGH is a series of violent expirations, at each of which the larynx is suddenly opened after the pressure of air in the lungs has risen considerably; its object is to expel some irritating substance from the air passages. SNEEZING is a single sudden expiration, which di?ers from coughing in that the sudden rush of air is directed by the soft palate up into the nose in order to expel some source of irritation from this narrow passage. CHEYNE-STOKES BREATHING is a type of breathing found in persons su?ering from stroke, heart disease, and some other conditions, in which death is impending; it consists in an alternate dying away and gradual strengthening of the inspirations. Other disorders of breathing are found in CROUP and in ASTHMA.... Medical Dictionary
Respiratory distress syndrome is a complication of SHOCK, systemic SEPSIS and viral respiratory infections. It was ?rst described in 1967, and – despite advances with assisted ventilation
– remains a serious disease with a mortality of more than 50 per cent. The maintenance of adequate circulating blood volume, peripheral PERFUSION, acid-base balance and arterial oxygenation is important, and assisted ventilation should be instituted early.
In newborns the mechanism is diferent, being provoked by an inability of the lungs to manufacture SURFACTANT.... Medical Dictionary
In humans the ‘normal’ temperature is around 37 °C (98·4 °F). It may rise as high as 43 °C or fall to 32 °C in various conditions, but the risk to life is only serious above 41 °C or below 35 °C.
Fall in temperature may accompany major loss of blood, starvation, and the state of collapse (see SHOCK) which may occur in severe FEVER and other acute conditions. Certain chronic diseases, notably hypothyroidism (see THYROID GLAND, DISEASES OF), are generally accompanied by a subnormal temperature. Increased temperature is a characteristic of many acute diseases, particularly infections; indeed, many diseases have a characteristic pattern that enables a provisional diagnosis to be made or acts as a warning of possible complications. In most cases the temperature gradually abates as the patient recovers, but in others, such as PNEUMONIA and TYPHUS FEVER, the untreated disease ends rapidly by a CRISIS in which the temperature falls, perspiration breaks out, the pulse rate falls, and breathing becomes quieter. This crisis is often preceded by an increase in symptoms, including an epicritical rise in temperature.
Body temperature is usually measured on the Celsius scale, on a thermometer reading from 35 °C to 43·3 °C. Measurement may be taken in the mouth (under the tongue), in the armpit, the external ear canal or (occasionally in infants) in the rectum. (See also THERMOMETER.)
Treatment Abnormally low temperatures may be treated by application of external heat, or reduction of heat loss from the body surface. High temperature may be treated in various ways, apart from the primary treatment of the underlying condition. Treatment of hyperthermia or hypothermia should ensure a gradual return to normal temperature (see ANTIPYRETICS.... Medical Dictionary
Although the risks are nil or very small with most drugs, no medication should be given to a pregnant woman, particularly during the ?rst few months of pregnancy, unless it is absolutely essential for her health or that of her unborn child. Alcohol is regarded as ‘medication’ in this context.... Medical Dictionary
Symptoms The onset may be sudden or insidious. In the acute form there is severe diarrhoea and the patient may pass up to 20 stools a day. The stools, which may be small in quantity, are ?uid and contain blood, pus and mucus. There is always fever, which runs an irregular course. In other cases the patient ?rst notices some irregularity of the movement of the bowels, with the passage of blood. This becomes gradually more marked. There may be pain but usually a varying amount of abdominal discomfort. The constant diarrhoea leads to emaciation, weakness and ANAEMIA. As a rule the acute phase passes into a chronic stage. The chronic form is liable to run a prolonged course, and most patients su?er relapses for many years. SIGMOIDOSCOPY, BIOPSY and abdominal X-RAYS are essential diagnostic procedures.
Treatment Many patients may be undernourished and need expert dietary assessment and appropriate calorie, protein, vitamin and mineral supplements. This is particularly important in children with the disorder. While speci?c nutritional treatment can initiate improvement in CROHN’S DISEASE, this is not the case with ulcerative colitis. CORTICOSTEROIDS, given by mouth or ENEMA, help to control the diarrhoea. Intravenous nutrition may be required. The anaemia is treated with iron supplements, and with blood infusions if necessary. Blood cultures should be taken, repeatedly if the fever persists. If SEPTICAEMIA is suspected, broad-spectrum antibiotics should be given. Surgery to remove part of the a?ected colon may be necessary and an ILEOSTOMY is sometimes required. After recovery, the patient should remain on a low-residue diet, with regular follow-up by the physician, Mesalazine and SULFASALAZINE are helpful in the prevention of recurrences.
Patients and their relatives can obtain help and advice from the National Association for Colitis and Crohn’s Disease.... Medical Dictionary
(2) A penis-shaped, battery-driven device used by women to attain sexual stimulation and climax.... Medical Dictionary