Asthma

Question 1

Pathology of asthma

Answer 1

Acute asthma is the result of an increase in inflammation of the airways as well as bronchospasm of the bronchial smooth muscles.

Question 2

Symptoms of asthma exacerbation

Answer 2

Shortness of breath, a non-productive cough, wheezing in all lung fields, and chest tightness due to a decrease in expiratory airflow. Patients typically present with symptoms that occur progressively over hours, days or weeks.

Question 3

What is the most common trigger of an asthma exacerbation?

Answer 3

The most common trigger of acute asthma is an upper respiratory tract infection.
- Those who present with sudden worsening of their symptoms are more frequently triggered by respiratory allergens, exercise, and psychosocial stress.

Question 4

When should a patient with asthma be intubated?

Answer 4

Severe respiratory distress AND one of the following:

• β2-adrenergic agonists (albuterol) or other medical therapies do not reverse symptoms
• Significant hypoxia even with supplemental oxygen
• Too tired to continue breathing on their own

Question 5

What is the initial treatment and goal?

Answer 5

• Oxygen
• LABA: If this has not been done, the device is easy to put together and is connected to the green oxygen port and turned on with 6-8 L/min. Albuterol is a 0.5% solution that is mixed with 2 mL of saline and is placed in the nebulizer by unscrewing the top of the canister.
• Goal to keep O2 above 92%

Question 6

Other options if albuterol isn’t enough?

Answer 6

• For patients who do not respond initially to albuterol, or who have a moderate to severe exacerbation, oral or intravenous corticosteroids should be administered early in the presentation. Onset of action is 4-6 hours.
• If severe, subcutaneous epinephrine 0.2 mg or terbutaline 0.25 mg should be administered. Epinephrine is known to cause bronchodilation, but also has β1 and α-effects which can lead to side effects such as tachycardia or myocardial ischemia.

Question 7

What is the most useful bedside test?

Answer 7

Pulmonary Function Tests (PFTs) performed at the bedside are the most useful objective test to aid in the treatment and disposition of a patient with an acute exacerbation of asthma. These tests confirm that the patient’s symptoms are due to obstructive lung disease, assess the severity of the exacerbation, and monitor the response to treatment.

Question 8

What are PFTs

Answer 8

PFTs are measured by using a peak expiratory flow rate (PEFR) meter or a handheld spirometry machine that determines the forced expiratory volume in one second (FEV1) (see figures). Both devices measure the velocity of air flow and degree of airway obstruction. They are simple to use, but effort dependent. These values are obtained upon presentation to the emergency department and after each β2-adrenergic agonists treatment with the best predictor being the results at 1 hour after initiation of treatment.

Question 9

How to interpret PFTs

Answer 9

PEFRs obtained with a peak flow meter are interpreted using standard tables listing the normal values expected based on the sex, age and height of the patient. For example, a 35 year old man who is 5 foot 10 inches tall would have a predicted PEFR of 609. If that patient recorded a PEFR of 300, he is at approximately 50% of his predicted rate.

Question 10

How do you diagnose asthma severity?

Answer 10

In general, asthma severity is divided up into mild exacerbations (> 70% predicted or personal best of PEFR), moderate exacerbations (40-69% predicted or personal best of PEFR) or severe exacerbations (<40% predicted or personal best of PEFR).

Question 11

What is the initial therapy?

Answer 11

The first line therapy for acute asthma in the ED is inhaled β2-adrenergic agonists (available as albuterol) in all age groups.
- Albuterol has an onset of action of 5 minutes and duration of action of 6 hours.

Question 12

Side effects of Albuterol?

Answer 12

tremor, tachycardia and mild hypokalemia due to potassium being driven into muscle cells

Question 13

Other treatment options:

Answer 13

• Anti-cholinergic: Ipratropium is an anticholinergic agent used in severe asthma or Beta-blocker induced asthma.
• Corticosteroids: Corticosteroids are administered to reduce airway inflammation during exacerbations of acute asthma.
• Epi: The Beta-agonist activity of epinephrine produces bronchodilatation. Epinephrine is reserved for patients who are seriously ill and not responding to serial treatments with inhaled β2-adrenergic agonists therapy.

Question 14

When are steroids indicated?

Answer 14

• Indicated in moderate to severe asthma exacerbations and in those who fail to respond to β2-adrenergic agonist therapy.
• Onset of action is 4-6 hours, but it may take up to 24 hours to exert a significant clinical effect.
• The administration of corticosteroids in the acute setting has been shown to reduce the number of recurrent attacks after an exacerbation. Inhaled corticosteroids are a safe and effective treatment to prevent acute asthma.

Question 15

Epinephrine dosage

Answer 15

The adult dose is 0.3-0.5 mg IM q20min and the pediatric dose is 0.01 mg/kg up to 0.3-0.5 mg IM q20min, both given for up to 3 doses

Question 16

What about antibiotics?

Answer 16

Antibiotics should be reserved for patients with evidence of bacterial infection. There is no evidence that routine antibiotic dosing in acute asthma is beneficial.