Most patients with asthma exacerbations do not require any initial laboratory or radiographic testing. Chest radiography is indicated in febrile patients and should be obtained for patients with productive cough and those with suspected cardiac or pulmonary disease, such as congestive heart failure, pneumothorax, pneumomediastinum, pneumonia, or atelectasis. A complete blood count could be helpful in patients with fever, although leukocytosis is common with asthma exacerbations, and steroids can also cause elevations in neutrophils within 1 to 2 hours of administration. Arterial blood gas analysis should be performed in patients with carbon dioxide retention, suspected hypoventilation, severe exacerbations, or a predicted peak flow of 25% or less after initial treatment.1 A normal carbon dioxide level is actually a poor prognostic indicator, as patients usually have a decreased carbon dioxide level from an increased respiratory drive.
No initial laboratory studies are required.
1. National Asthma Education and Prevention Program. Expert panel report 3: guidelines for the diagnosis and management of asthma (EPR-3 2007). NIH Publication No. 08–4051. Bethesda (MD): U.S. Department of Health and Human Services; National Institutes of Health; National Heart, Lung, and Blood Institute; 2007. Available at www.nhlbi.nih.gov/guidelines/asthma/asthgdln.htm. Accessed 22 Jul 2008.
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Seminars in Medical Practice
Hospital Physician Board Review Manuals
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Updated 9/22/08 nvf