Pharmacotherapy of Asthma
PST 06106
Basic Pharmacotherapy
Session 21: Pharmacotherapy of Asthma
Learning Objectives
By the end of this session students are expected to be able to:
Define asthma
Explain pathophysiology of asthma
Explain the clinical presentation of asthma
Outline diagnosis asthma
Describe pharmacological treatment of asthma
Describe the monitoring of
asthma
Activity: Buzzing
What is
Asthma
?
Definition of Asthma
Asthma is a common, chronic respiratory disease
of the airways of the lung characterized by either the intermittent or persistent presence of highly variable degrees of airflow obstruction from airway wall inflammation and bronchial smooth muscle constriction.
People with asthma experience episodes of wheezing, breathlessness and chest tightness due to widespread narrowing of the airways.
The cause of
Asthma
is
unknown
but the risk if associated with genetics and
environmental
factors.
Genetic factors account for 60% to 80% of the susceptibility.
Asthma represents a complex genetic disorder in that the asthma phenotype is likely a result of polygenic inheritance or different combinations of genes
Definition of
Asthma Cont.…..
Environmental risk factors for the development of asthma include;
S
ocioeconomic
status,
F
amily
size,
E
xposure
to secondhand tobacco smoke in infancy and in utero,
A
llergen
exposure
U
rbanization
,
R
espiratory
syncytial virus infection, and
E
xposure
to common childhood infectious
agents
List of agents and events Triggering Asthma
Pathophysiology Of Asthma
The major characteristics of asthma include a variable degree of airflow obstruction (related to bronchospasm, edema, and mucus hypersecretion) and airways inflammation
To understand the pathogenetic mechanisms that underlies the many phenotypes of asthma, it is critical to identify factors that initiate, intensify, and modulate the inflammatory response of the airways and to determine how these processes produce the characteristic airway abnormalities
.
Pathophysiology Of Asthma
Cont
….
The immunohistopathologic features of asthma include inflammatory cell infiltration:
Neutrophils (especially in sudden-onset, fatal asthma exacerbations; occupational asthma, and patients who smoke)
Eosinophils
Lymphocytes
Mast cell activation
Epithelial cell injury
P
athophysiology
of Asthma cont.
…
Airway inflammation contributes to airway
hyper responsiveness,
airflow limitation, respiratory symptoms, and disease chronicity.
In some patients, persistent changes in airway structure occur, including sub-basement fibrosis, mucus hypersecretion, injury to epithelial cells, smooth muscle hypertrophy, and angiogenesis.
Gene-by-environment interactions are important to the expression of asthma.
Atopy, the genetic predisposition for the development of an immunoglobulin E (
IgE
)-mediated response to common aeroallergens, is the strongest identifiable predisposing factor for developing asthma
.
Viral respiratory infections are one of the most important causes of asthma exacerbation and may also contribute to the development of asthma
Clinical Presentation And Diagnosis Of Asthma
Clinical Presentation is divided into
Acute Asthma
Chronic
asthma
Acute asthma
General
An episode can progress over several days or hours (usual scenario) or progresses rapidly over 1 to 2 hours
.
Clinical Presentation And Diagnosis Of Asthma
Acute
asthma…..
Symptoms
The patient is anxious in acute distress and complains of severe dyspnea , shortness of breath, chest tightness, or burning and wheezing sound
The patient is only able to say a few words with each breath.
Symptoms are unresponsive to usual measures (
shortacting
inhaled
β
2 –agonist administration).
Clinical Presentation And Diagnosis Of
Asthma
Cont
…
Acute
asthma…..
Signs
Signs
include expiratory and inspiratory wheezing on auscultation (breath sounds may be diminished with very severe obstruction),
D
ry
hacking cough,
T
achypnea
,
T
achycardia
,
P
ale
or cyanotic skin,
Hyper inflated
chest with intercostal and supraclavicular retractions, and
Hypoxic seizures if very severe
Clinical Presentation And Diagnosis Of Asthma
Cont
…
Acute
asthma……
Laboratory
PEF(peak expiratory flow)
and/or
FEV(Forced expiratory volume 1)
less than 40% of normal predicted values.
Decreased arterial oxygen (
PaO
2 ), and O 2 saturations by pulse oximetry (
SaO
2 less than 90% on room air is severe).
Increased
arterial or capillary CO 2 if mild, but in the normal range or increased in moderate to severe obstruction
.
Clinical Presentation And Diagnosis Of Asthma
Cont
…
Acute
asthma…
Other
Diagnostic Tests
Blood gases to assess metabolic acidosis (lactic acidosis) in severe obstruction.
Complete blood count if there are signs of infection (fever and purulent sputum).
Serum electrolytes as therapy with
β
2 -agonist and corticosteroids can lower serum potassium, magnesium, and phosphate, and increase glucose.
Chest radiograph if signs of consolidation on auscultation
Clinical Presentation And Diagnosis Of Asthma
Cont
…
Chronic Asthma
General
Asthma is a disease of exacerbation and remission, so the patient may not have any signs or symptoms at the time of exam.
Symptoms
The patient may complain of episodes of dyspnea, chest tightness, coughing (particularly at night), wheezing, or a whistling sound when breathing.
These often occur in association with exercise, but also occur spontaneously or in association with known allergens
.
Clinical Presentation And Diagnosis Of Asthma
Cont
…
Chronic
Asthma….
Signs
Expiratory wheezing on auscultation, dry hacking cough, or signs of atopy (allergic rhinitis and/or eczema) may occur.
Laboratory
Spirometry demonstrates obstruction (reduced FEV 1 /FVC(forced vital capacity) with reversibility following inhaled
β
2 -agonist administration (at least a 12% improvement in FEV 1).
Clinical Presentation And Diagnosis Of Asthma
Cont
…
Chronic
Asthma…..
Other
Diagnostic Tests
A
fall in FEV 1 of at least 15% following 6 minutes of near maximal exercise.
Elevated eosinophil count and
IgE
concentration in blood.
).
Activity
: Small Group Discussion
What is the treatment of
Asthma ?
Pharmacological Treatment of Asthma
Acute Severe Asthma
The primary goal is prevention of life-threatening asthma by early recognition of signs of deterioration and early intervention.
The principal goals of treatment include:
Correction of significant
hypoxemia ( A low level of oxygen in the blood)
Rapid reversal of airflow obstruction
Reduction of the likelihood of relapse of the exacerbation or future recurrence of severe airflow obstruction
Treatment of asthma according to severity
Pharmacological Treatment of
Asthma Cont..
Chronic Asthma in Adults
The assessment of the frequency of daytime and nighttime symptoms and limitation of physical activity determines whether asthma is intermittent or persistent.
There are 4 categories.
Therapy is step-wise (Step 1–4) based on the category of asthma and consists of:
Preventing the inflammation leading to bronchospasm (controllers)
Relieving bronchospasm (relievers)
Controller medicines in asthma
Inhaled corticosteroids e.g. Beclomethasone
Reliever medicines in asthma
Treatment
of Chronic Asthma According to
Severity
Monitoring Of Asthma Therapy
Lung function, either
spirometry
or peak flow measurements, should be monitored 5 to 10 minutes after each treatment.
Oxygen saturations can be easily monitored continuously with pulse oximetry.
For young children and infants, pulse oximetry, lung auscultation, and observation of the presence of supraclavicular retractions are useful.
The majority of patients will respond within the first hour of initial inhaled
β
2 -agonists regardless of history of home administration of drug.
Patients not achieving an initial response should be monitored every half hour to 1 hour.
Depending on whether there is a standard ED or a special unit for acute severe asthma, the decision to admit to the hospital should be made within 4 to 6 hours of entry to the emergency
department
Key Points
Asthma
is a common, chronic respiratory disease
of the airways of the lung characterized by either the intermittent or persistent presence of highly variable degrees of airflow obstruction from airway wall inflammation and bronchial smooth muscle constriction.
Symptoms of Asthma include
severe dyspnea, shortness of breath, chest tightness, or burning and wheezing sound
The principal goals of treatment of Asthma include correction of significant hypoxemia
and rapid reversal of airflow obstruction by using pharmacological and non pharmacological therapy
Evaluation
What
is Asthma?
What is the pathophysiology of
Asthma?
What are the signs and symptoms of Asthma?
How is the treatment of asthma?
References
Wells
BG,
DiPiro
J,
Schwinghammer
T (2013),
Pharmacotherapy Handbook
(6
th
Ed). New York, NY: McGraw-Hill.
DiPiro
JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey ML, (2008):
Pharmacotherapy: A Pathophysiologic Approach
(7
th
ed
): New York, NY: McGraw-Hill.
Katz M D., Matthias KR., Chisholm-Burns M A., Pharmacotherapy(2011)
Principles & Practice Study Guide: A Case-Based Care Plan Approach
: New York, NY: McGraw-Hill.
Schwinghammer
TL, Koehler JM (2009)
Pharmacotherapy Casebook: A Patient-Focused Approach
(7
th
ed
): New York, NY: McGraw-Hill.
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