 |
Contents | Director | One | Two | Article | Topic 1 | Topic 2 | EKG | Rad 1 | Rad 2 Albany Medical Review - May 2002 |
|
Review -
|
|
David Fenton, MD
Asthma is an inflammatory disease of the airways. It is characterized by its reversible, reactive nature. Asthma is not progressive, but is rather notable for episodes of exacerbations and remissions. Its symptoms are a result of airflow obstruction and include dyspnea, cough, wheezing, and chest tightness. The classic triad consists of cough, wheeze, and dyspnea. Traditionally, symptoms are worse at night or early in the morning. Airflow obstruction is caused by airway smooth muscle contraction, vascular congestion, bronchial edema, and thick secretions. The heightened airway reactivity can either be allergic or idiosyncratic in origin. Common allergens include dust mites, roaches, cats, and seasonal pollens. Other possible precipitants include tobacco and air pollution, exercise, upper respiratory infections, reflux (GERD), and medications (ie aspirin, beta antagonists, coloring agents, and sulfating agents). Asthma is a relatively common disease–affecting approximately 26 million individuals or roughly 10% of the population. Fortunately, of those affected, 70% are classified as having "mild" disease, 20% "moderate" disease, and only 10% "severe" disease. In addition, it is an expensive disease. More than $6 billion were spent on asthma related care in 1990 for example. Asthma accounts for 470,000 hospital admissions and 10 million office visits a year. It is also responsible for 5,000 deaths a year in the U.S. Incidence is equal between males and females by age 30. However, asthma is more prevalent in early life. In fact, 80% of asthmatics are younger than 45 years old. Patients are often identified after presenting with some or all of the above classic symptoms, and confirmation of the disease is achieved by spirometry. Spirometry shows diminished airflow or a positive bronchial provocation challenge. The bronchial challenge is to methacholine/histamine, and is considered positive with a decrease in FEV1 of 20% from baseline (with 16 mg/ml of solution used). The diminished airflow is either completely or partially reversible (spontaneously or following bronchodilator treatment). Reversibility is evidenced by an increase of 12% or 200 ml in FEV1. It is based on spirometry and symptomatology that asthma severity is classified. Table 1 shows this stratification of asthma severity. Given the breadth of asthma as a topic, this paper will review only the long-term management of asthma. There are several goals with long-term management: minimize chronic symptoms, prevent exacerbations, decrease the number of emergency room visits and hospital admissions, maintain near normal patient pulmonary function, maintain near normal patient activity levels, and use medications with the fewest side effects. Keeping these goals in mind, the best treatment plan relies on a stepwise approach to long-term asthma management. The stepwise approach is based on the patient’s severity of asthma and response to treatment modalities (ie medications). Effective long-term management of asthma requires a few fundamental principles: 1) patient education, 2) medication, and 3) appropriate follow-up and monitoring. Patient education is essential for optimal compliance with treatment regimens and necessary self-monitoring. Initial education should consist of providing patients with basic knowledge of asthma itself (ie definition, treatment, triggers, testing, etc…). Once patients have an understanding of asthma, then education can proceed to developing appropriate action plans. These written action plans should instruct patients on when/how to adjust their medications, when to contact their physician with problems, and how to recognize the need for emergent ER visits. This fundamental education process should be an ongoing practice and invite patients to be pro-active. The next step after patient education is the utilization of medications. There are many medications available now for effective long-term asthma treatment. However, the cornerstone of daily long-term medication use is an anti-inflammatory agent. The success of anti-inflammatory agents is based on countering the very nature of asthma–a reactive/inflammatory disease. Daily medication use is often not warranted until the patient is classified as having mild persistent asthma or worse. Once again, a stepwise approach to medication use is important. The basic principle is to make treatment changes based on the patient’s severity of asthma and response to previous treatment regimens. Initially, treatment should be started at a higher level than normally warranted by a patient’s severity (for rapid control) and then stepped down to a steady level of care as symptoms permit. Table 2 provides a general overview. The primary medications utilized for long-term asthma management are corticosteroids (glucocorticoids), cromolyn/nedocromil, beta agonists, theophylline (methylxanthines), and leukotriene inhibitors. Inhaled glucocorticoids are the mainstay of treatment with systemic steroids used primarily only for short term "burst" control and severe persistent asthmatics. Corticosteroids simply work by decreasing inflammation and potentiating beta agonist response. They reduce airway hyperresponsiveness, inhibit cytokines, and interfere with inflammatory cell migration and activation. Potential adverse effects include cough, hoarse voice, candidiasis, and possibly systemic effects with high doses (studies not conclusive). Mouth washing after MDI use can substantially reduce these adverse effects. Cromolyn and nedocromil also work as anti-inflammatory agents. They modulate mast cell mediator release and eosinophil recruitment. Nedocromil has proven more effective than cromolyn in studies. Both agents are especially safe with only occasional unpleasant taste as a reported adverse effect. Beta agonist agents are another effective class of medication for asthma. Long-acting agents are more effective for long-term asthma control, but short-acting agents are useful for asthma exacerbations. Beta agonists work primarily through their bronchodilator capacity. They cause smooth muscle relaxation by increasing cyclic AMP levels within the muscle cells. Beta agonists are especially useful as add-on agents to corticosteroids. Potential adverse effects are limited but include tachycardia, skeletal muscle tremor, hypokalemia, and QTc prolongation in overdose. Theophylline (methylxanthines) also works as a bronchodilator, but may also have mild anti-inflammatory properties. It causes smooth muscle relaxation by phosphodiesterase inhibition, and may also affect eosinophilic infiltration into bronchial mucosa. In addition, theophylline increases mucociliary clearance and augments diaphragm contractility. It is useful as an adjuvant for moderate/severe persistent asthma. However, theophylline requires close monitoring of its serum concentration due to its narrow toxic-therapeutic range. Acute toxicities include tachycardia, nausea and vomiting, tachyarrhythmias (SVT), CNS stimulation, headache, seizures, hematemesis, hyperglycemia, and hypokalemia. The last common class of long-term medications for asthma is leukotriene inhibitors. These agents include Zafirlukast and Zileuton. There is a wide range of effect between patients with these agents. Both agents reduce the inflammatory response produced by leukotrienes. Zileuton works by inhibiting 5-lipoxygenase, and Zafirlukast acts as a selective competitive inhibitor of leukotriene receptors. This class is still being studied to determine its exact role in long-term asthma management and possible adverse effects on the liver. An additional category of medications for the management of asthma is quick-relief medications for asthma exacerbations. These agents are part of any long-term management plan and include short-acting beta agonists, anticholinergics, and systemic corticosteroids. The final fundamental principle in effective long-term asthma management is appropriate follow-up and monitoring. Monitoring should be done both by a physician and the patient (self-assessment). Patients should have office visits at least every 6 months. During these visits, the physician should review the patient’s clinical history (including sleep quality, capacity for daily activities and exercise, and possible asthma triggers), check the patient’s written action plan, review important teaching points (including MDI technique and compliance with medications), and check objective tests of pulmonary function. Monitoring of pulmonary function includes following frequent peak flow meter readings at home and more accurate clinical spirometry. Spirometry should be done at the patient’s initial assessment, once stabilized on chronic treatment, and at least every 1-2 years thereafter. Other issues related to long-term management of asthma are as follows. Patients should be made aware of potential allergens and asthma triggers. These agents should be actively avoided or removed to prevent exacerbations and protect lung function. Desensitization or immunotherapy may also be helpful in more allergy sensitive patients. Next, patients likely benefit from annual flu shots and a pneumovax vaccine. These vaccines are protective in patients with underlying lung disease (ie asthmatics). Finally, some patients may require specialized care from an asthma specialist. Patients with difficulty achieving or maintaining asthma control and those with step 4 care (severe persistent asthma) should be considered for consultation or comanagement by a specialist.
REFERENCES
|
|
Albany
Medical Center |
E-mail the AMC Webmaster: Webmaster@mail.amc.edu |
|
30.01.2002 |
|
