Master the board step 3

Master the Boards: USMLE Step 3
Answer: D. Methacholine stimulation testing looks for a decrease in FEV 1 in response
to synthetic acetylcholine. Methacholine will decrease FEV 1 if the patient has asthma.
The DLCO is a good test of interstitial lung disease, in which it is decreased. Asthmatic
patients may have an increased DLCO from hyperventilation. High-resolution CT scanning
is a test for interstitial lung disease and for bronchiectasis. Pre- and postbronchodilation
PFTs are an appropriate assessment if the patient is currently short of breath to
see if there is improvement, but they are of no value in an asymptomatic patient. Chest
x-ray is not specific enough to be the “most accurate test.”
All patients with shortness
of breath should receive
the following:
• Oxygen
• Continuous oximeter
• Chest x-ray
• Arterial blood gas (ABG)
Treatment
The best initial therapies, which should be ordered with the first screen on
CCS, are the following:
··
Inhaled bronchodilators (albuterol): There is no maximum dose of inhaled
bronchodilators.
··
Bolus of steroids (methyl prednisolone): Steroids need 4–6 hours to be
effective.
··
Inhaled ipratropium
··
Oxygen
··
Magnesium
Any patient with asthma and respiratory acidosis with CO 2 retention should
be placed in the ICU. Persistent respiratory acidosis is an indication for intubation
and mechanical ventilation.
Acute Asthma
The following therapies have no benefit for acute asthma exacerbation:
If there is an indication
for beta blockers that
decreases mortality in an
asthmatic, then use the
beta blocker.
··
Theophylline
··
Cromolyn and nedocromil
··
Montelukast
··
Inhaled corticosteroids
··
Omalizumab (anti-IgE)
··
Salmeterol and long-acting beta agonists
··
Epinephrine: Subcutaneously administered epinephrine has no benefit in
addition to inhaled bronchodilators.
··
Terbutaline: Terbutaline is less efficacious than inhaled albuterol. Terbutaline
is always a wrong answer choice.
Basic Science Correlate
Omalizumab is an IgG against IgE. Decreasing IgE decreases activation and
release of mast cells.
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