Medical Pharmacology Chapter 25: Pulmonary Pharmacology--Asthma
1Asthma is most correctly defined as a chronic inflammatory airway disease associated with excessive tracheobronchial reactivity.
The reactive airway may be provoked by a number of stimuli.
Airway constriction may resolve following pharmacological intervention or spontaneously; however, manifestations including wheezing, cough, and dyspnea are prevalent.
Before considering implications of asthma and other pulmonary disease in the context of preoperative, and properties, and postoperative anesthesia management, we'll consider basic physiological, pathophysiological, and biochemical aspects of pulmonary disease generally.
"Asthma is a chronic inflammatory disorder of the airway is, in which many cells and cellular elements play a role, in particular, mast cells, eosinophils, T-lymphocytes, macrophages, neutrophils, and epithelial cells.
In susceptible individuals, this inflammation causes recurrent episodes of wheezing, restlessness, chest tightness, and coughing, particularly at night or early morning.
These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment.
The inflammation also causes an associated increase in the existing bronchial hyperresponsiveness to a variety of stimuli."--Expert Panel of the National Institutes of Health, National Asthma Education and Prevention Program (NAEPP)
By way of background, asthma is characterized by relatively asymptomatic periods with occasional acute attacks.
These episodes may resolve fairly rapidly pursuant to pharmacological intervention; moreover, sometimes patients may chronically experienced some degree of airway resistance.
A serious condition, status asthmaticus, occurs when significant obstruction persists for extended periods.
Status asthmaticus is defined as a therapeutic emergency.
Asthma affects about 5% of the United States population, which corresponds to about 14-15 million individuals in the United States.
This frequency is comparable to that observed in other countries.
Typically asthma is first noted early in life, although it occurs at all ages.
In terms of age distribution about 50% of cases are noted in patients less than 10 years of age with another 33% occurring before the age of 40.
Initially (childhood), males appear about twice as likely to present with asthma as females; however, this the gender difference is not noted following the age of 30.
Asthma, affecting about 5 million children, is the most common chronic illness among children with minorities particularly affected.
African-American individuals exhibit about 19% higher asthma incidence compared to whites and are two times more likely to be hospitalized for asthma.
Based on 1990 data, about 10 million schooldays were missed due to asthma resulting in a cost of about $1 billion due to lost family income.
Another concern is the trend indicated in the timeframe from 1980-1993 that the "age-specific" death rate due to asthma increased file over twofold.
Asthma mortality appears highest among African-American individuals indicated by a 400% higher likelihood of death compared to other groups.
From the point acute classification, one approach has been to categorize based on the factor(s) that precipitate the occurrence, although this approach may be overly simplistic given the heterogeneous nature of asthma.
Generally, following this approach, "allergic" and "idiosyncratic" are the two principal types of asthma classifications.
1Atopy constitutes the largest risk factor for asthma ("hereditary allergy characterized by symptoms (e.g. as asthma, hayfever, or hives) produces upon exposure to the exciting antigen without inoculation" Merriam-Webster Collegiate dictionary) development.
1Allergic asthma is associated with a family history (or personal history) of allergic diseases including urticaria (hives), rhinitis, and/or eczema with positive wheal-and-flare reactions to intradermal injection of airborne antigen extracts and would be associated with increased levels of serum IGE and/or positive response to specific inhaled antigen.
1Many individuals do not exhibit personal/family allergy history and shell normal IGE serum levels and negative skin tests.
Consequently, this type of asthma is not classified within immunological context and is instead described as idiosyncratic asthma.
In this setting the initial provocative event for asthma development may be an upper respiratory illness.
In particular, the initial event could be a common cold but wheezing and dyspnea which may last four days-months may be exhibited within a few days.
This phenomenon is different from an individual with chronic bronchitis or bronchiectasis and could then manifest bronchospasm as a consequence.
1 McFadden, E.R., Jr. "Asthma: Diseases of the Respiratory System" in Harrison's Principles of Internal Medicine, 15th Edition (Braunwald, E., Fauci, A.S., Kasper, D.L., Hauser, S.L, Longo, D.L. and Jameson, J. Larry, eds) pp. 1456-1463, McGraw-Hill Medical Pubishing, Division, New York, 2001
2 Kelley, H. William, "Asthma" in Pharmacotherapy: A Pathophysiologic Approach, (Dipiro, J.T., Talkbert, R.L. Yee, G.C., Matze, G.R., Wells, B.G. and Posey, L. Michael, eds.) pp 430-459. McGraw-Hill Medical Pubishing, Division, New York, 1999.
3Spencer SM., Sgro JY., Dryden KA., Baker TS., Nibert ML. (1997) Rhinovirus 14 (3D image reconstruction from electron microscopy data) Journal of Structural Biology. 120(1):11-21
4Attribution: Michigan State University Website
5Hacohen, N. Dendritic cell responses to diverse antigens
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6McClay, J.E., Nasal Polyps, eMedicine (Pediatrics, Otolarygnology)