Asthma airway obstruction

Individuals with certain chronic illnesses and medical conditions may also suffer severe and potentially fatal side effects from the use of nitrous oxide. For example, anyone with a history of pulmonary hypertension, asthma, airway obstruction, head injury, or chest infection should not take nitrous under any circumstances. 

W ithin the past few years a number of new drugs have been introduced to treat respiratory disorders, such as bronchial asthma and disorders that produce chronic airway obstruction. This chapter discusses the bronchodilators, dragp that have been around for a long time but are still effective in specific instances, and the newer antiasthma drugs that have proven to be highly effective in the prophylaxis (prevention) of breathing difficulty. 

Asthma is a reversible obstructive disease of the lower airway. With asthma there is increasing airway obstruction caused by bronchospasm and bronchoconstriction, inflammation and edema of the lining of the bronchioles, and the production of thick mucus that can plug the airway (see Pig. 37-1). There are three types of asthma ... 

Sympathomimetics (drugs that mimic the sympathetic nervous system) are used primarily to treat reversible airway obstruction caused by bronchospasm associated with acute and chronic bronchial asthma, exercise-induced bronchospasm, bronchitis, emphysema, bronchiectasis (abnormal condition of the bronchial tree), or other obstructive pulmonary diseases. 

Asthma is characterized by inflammation, airway hyperresponsiveness (AHR), and airway obstruction. Inhaled antigens... 

Bronchial asthma is defined as a chronic inflammatory disease of the lungs it affects an estimated 9 to 12 million individuals in the U.S. Furthermore, its prevalence has been increasing in recent years. Asthma is characterized by reversible airway obstruction (in particular, bronchospasm), airway inflammation, and increased airway responsiveness to a variety of bronchoactive stimuli. Many factors may induce an asthmatic attack, including allergens respiratory infections hyperventilation cold air exercise various drugs and chemicals emotional upset and airborne pollutants (smog, cigarette smoke). 

The desired outcome in the pharmacological treatment of asthma is to prevent or relieve the reversible airway obstruction and airway hyperresponsiveness caused by the inflammatory process. Therefore, categories of medications include bronchodilators and anti-inflammatory drugs. 

The history and physical examination should be obtained while initial therapy is being provided. A history of previous asthma exacerbations (e.g., hospitalizations, intubations) and complicating illnesses (e.g., cardiac disease, diabetes) should be obtained. The patient should be examined to assess hydration status use of accessory muscles of respiration and the presence of cyanosis, pneumonia, pneumothorax, pneumomediastinum, and upper airway obstruction. A complete blood count may be appropriate for patients with fever or purulent sputum. 

Objective measurements of airflow obstruction with a home peak flow meter may not necessarily improve patient outcomes. The NAEPP advocates use of PEF monitoring only for patients with severe persistent asthma who have difficulty perceiving airway obstruction. 

An inhalable medication that relaxes the muscles in the airways (bron-chodilator) is frequently administered when airways obstruction is identified. In this bronchodilator trial test, the spirometry test is subsequently repeated and compared to the results from the initial spirometry test. If there is substantial improvement in lung function with the administration of the bronchodilator, the airways obstruction is reversible. An example of a lung disease with reversible airways obstruction is asthma, in which s)nnptoms occur episodically when airways obstruction occurs. If there is little or no improvement after the administration of the bronchodilator, the airways obstruction is fixed. An example of a limg disease with fixed airways obstruction is BO, where there is scarring of the airways. 

Exposure to and inhalation of concentrations of 2500-6500ppm, as might result from accidents with liquid anhydrous ammonia, cause severe corneal irritation, dyspnea, bron-chospasm, chest pain, and pulmonary edema that may be fatal. Upper airway obstruction due to laryngeal/pharyngeal edema and desquamation of mucous membranes may occur early in the course and require endotracheal intubation or tracheostomy. " Case reports have documented chronic airway hyperreactivity and asthma, with associated obstructive pulmonary function changes after massive ammonia exposures. ... 

Injection - Heart failure secondary to chronic lung disease cardiac arrhythmias brain tumor acute alcoholism delirium tremens idiosyncrasy to the drug increased intracranial or CSF pressure head injuries acute bronchial asthma upper airway obstruction. Because of its stimulating effect on the spinal cord, morphine should not be used in convulsive states (eg, status epilepticus, tetanus, strychnine poisoning) concomitantly with MAOIs or in those who have received such agents within 14 days. 

Epidural/Intrathecal- Presence of infection at the injection microinfusion site concomitant anticoagulant therapy uncontrolled bleeding diathesis parenterally administered corticosteroids within a 2-week period, other concomitant drug therapy or medical condition that would contraindicate the technique of epidural or intrathecal analgesia acute bronchial asthma upper airway obstruction. 

DepoDur- Respiratory depression acute or severe bronchial asthma upper airway obstruction paralytic ileus head injury increased intracranial pressure circulatory shock. 

Oxymorphone Hypersensitivity to morphine analogs acute asthma attack severe respiratory depression or upper airway obstruction paralytic ileus pulmonary edema secondary to a chemical respiratory irritant. 

Epidural/Intrathecal administration Limit epidural or intrathecal administration of preservative-free morphine and sufentanil to the lumbar area. Intrathecal use has been associated with a higher incidence of respiratory depression than epidural use. Asthma and other respiratory conditions The use of bisulfites is contraindicated in asthmatic patients. Bisulfites and morphine may potentiate each other, preventing use by causing severe adverse reactions. Use with extreme caution in patients having an acute asthmatic attack, bronchial asthma, chronic obstructive pulmonary disease or cor pulmonale, a substantially decreased respiratory reserve, and preexisting respiratory depression, hypoxia, or hypercapnia. Even usual therapeutic doses of narcotics may decrease respiratory drive while simultaneously increasing airway resistance to the point of apnea. Reserve use for those whose conditions require endotracheal intubation and respiratory support or control of ventilation. In these patients, consider alternative nonopioid analgesics, and employ only under careful medical supervision at the lowest effective dose. 

Since the bronchial tonus is under the relaxant influence of 62-adrenoceptor stimulation, especially unselective jS-blockers increase the respiratory resistance. In susceptible patients this might induce airway obstruction or even acute asthma. The blockade of jS2-adrenoceptors inhibits the mobilization of free fatty acids and glucose. This might result in hypoglycemia in diabetic patients. Furthermore, these patients will be not aware of the danger since most of the sympathetically mediated alerting symptoms like tachycardia are suppressed by the jS-blockers as well. jSi-Selective blockers show this type of side-effect less pronounced than unselective compounds. 

COPD is a chronic, slowly progressive disorder characterized by airways obstruction (FEVi < 80% predicted FEViA C ratio < 70%) which does not change markedly over several months. The airways obstruction is largely fixed but may be partially reversible by bronchodilator therapy. Unlike asthma, airflow limitation in COPD can never be returned to normal values. The diagnosis of COPD is usually suggested by symptoms. A firm diagnosis can only be made by objective measurement of airways obstruction with spirometric tests, which may be enhanced by radio diagnostic techniques (Table 4). 

Three factors contribute to airway obstruction in asthma (1) contraction of the smooth muscle that surrounds the airways (2) excessive secretion of mucus and in some, secretion of thick, tenacious mucus that adheres to the walls of the airways and (3) edema of the respiratory mucosa. Spasm of the bronchial smooth muscle can occur rapidly in response to a provocative stimulus and likewise can be reversed rapidly by drug therapy. In contrast, respiratory mucus accumulation and edema formation are likely to require more time to develop and are only slowly reversible. 

The principal use of theophylline is in the management of asthma. It is also used to treat the reversible component of airway obstruction associated with chronic obstructive pulmonary disease and to relieve dyspnea associated with pulmonary edema that develops from congestive heart failure. 

Based on the concept that asthma is an inflammatory disease that leads to airway obstruction, inhaled glucocorticoids are the first-line treatment for moderate to severe asthma. Inhaled preparations are particularly effective when used to prevent recurrent attacks. This therapy is often combined with an inhaled bron-chodUator such as a p-adrenergic agonist. The use of p-adrenergic agonists or theophylline enables use of a lower dose of glucocorticoid, especially in patients relatively resistant to therapy (see Chapter 39). 

Contraindications Paralytic ileus, acute asthma attack, pulmonary edema secondary to chemical respiratory irritant, severe respiratory depression, upper airway obstruction... 

It decreases reversible bronchospasm associated with chronic bronchitis, pulmonary emphysema, bronchial asthma, silicosis, tuberculosis and sarcoidosis. The resultant decrease in airway obstruction may relieve the dyspnea associated with bronchospasm. 

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