Sunday, December 11, 2005

asthma

asthma - Asthma is an airway disorder characterized by intermittent episodes of smooth-muscle spasm, mucosal edema, and retained thick secretions. It is marked by recurrent attacks of wheezing and dyspnea. These attacks are chronic and may be associated with emphysema. The degree of airflow obstruction is directly related to the severity of the above mechanisms. There are two types of asthma, immunologic and nonimmunologic. Immunologic or allergic asthma usually occurs in childhood. Nonimmunologic asthma usually develops in adults over 35 years of age. These attacks are precipitated by an infection in the sinuses and bronchial tree. Asthma can also be classified as mixed asthma, where attacks are initiated by viral or bacterial infections and allergens. Hypoxemia (lack of O2), hypercapnia (excess CO2), and the use of bronchodilators may lead to an acute asthmatic attack.
A careful history by the physician can be helpful in determining causative factors. These attacks often occur at night. The person experiences choking, dyspnea, and the characteristic wheezing sound. The person may become cyanotic and diaphorectic. Most attacks subside in 30 minutes to one hour. Treatment is aimed at symptomatic relief and control of specific causative factors. In people whose asthma is caused by contact with the allergen, an attempt may be made to desensitize this individual. However, this is rarely used with adult-onset asthmatics. Oxygen is usually not necessary unless the patient develops cyanosis. Oxygen may be given by nasal prong, mask, or intermittent positive pressure breathing.
Bronchodilators are divided into two groups: the adrenergic drugs, epinephrine and isoproterenol; and the xanthine derivatives, aminophylline and theophylline. These drugs reduce bronchospasm by causing relaxation of the smooth muscle lining of the bronchi and bronchioles. They are very effective when given by nebulizer. The effectiveness of bronchodilators is dependent on the dose and delivery of the drug into the lung. Overuse of these drugs can lead to loss of effectiveness and should be used cautiously in patients with arteriosclerotic heart disease.
Humidification of inspired air is important therapy. Dehydration of the respiratory mucous membrane can lead to bronchial asthma attacks. Humidification causes liquification of the secretions, which promotes more effective clearing of the airways. Increased fluid intake will help replace fluids lost by perspiration during an acute attack. The patient should avoid antihistamines. Sedatives and tranquilizers can be used to control anxiety. Care must be taken to avoid suppression of respirations and the cough reflex. Narcotics are avoided because of their respiratory depressant effects.
If the acute asthmatic state is complicated by an infection, it is treated with antibiotics. The environment should be as free as possible of factors that contribute to respiratory infections. The patient should be protected from exposure to allergens that may set off attacks.
See also EMPHYSEMA.
Phipps, W. J., et al. Medical Surgical Nursing Concepts and Clinical Practice. St. Louis: C. V. Mosby Co., 1983.
Scherer, J. C. Introductory Medical Surgical Nursing. Philadelphia: J. B. Lippincott Co., 1982.


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