From the Guidelines
For acute asthma exacerbation in the emergency department, laboratory testing should be limited and focused on ruling out complications or alternative diagnoses, with most patients not requiring laboratory studies unless there are signs of severe exacerbation or complications 1. When considering laboratory tests, it's essential to prioritize those that will guide management and avoid unnecessary testing.
- A complete blood count (CBC) may be considered to assess for leukocytosis, which could indicate infection 1.
- Arterial blood gas (ABG) measurements are helpful for evaluating PaCO2 in patients with suspected hypoventilation, severe distress, or those with FEV1 or PEF results of 25% or less of predicted value after initial treatment 1.
- Basic metabolic panel (BMP) can be used to check electrolytes and assess for dehydration.
- Peak expiratory flow (PEF) measurements and pulse oximetry are crucial for assessing severity and response to treatment, often more so than laboratory tests.
- In patients with fever or productive cough, sputum cultures or blood cultures may be warranted to identify potential infections.
- Theophylline levels should be checked in patients on this medication to monitor for toxicity. It's also important to consider the emotional impact of asthma symptoms on the patient and family, which can affect approaches to treatment and follow-up 1. The primary focus should remain on clinical assessment, response to bronchodilators, and oxygen saturation rather than laboratory values for the diagnosis and treatment of asthma exacerbations 1.
From the Research
Labs for Acute Asthma Exacerbation
When managing acute asthma exacerbation in the emergency department, the following labs may be considered:
- Arterial blood gas (ABG) measurements to assess the severity of respiratory failure and guide treatment decisions 2, 3
- Complete blood count (CBC) to rule out underlying infections or other conditions that may be contributing to the exacerbation
- Electrolyte panel to monitor for potential electrolyte imbalances, particularly in patients receiving repeated doses of beta-agonists
- Peak expiratory flow rate (PEFR) to assess the severity of airway obstruction and monitor response to treatment 4, 3
- Chest x-ray to rule out complications such as pneumonia or pneumothorax, although this is not routinely recommended for all patients with acute asthma exacerbation 4, 3
Rationale for Lab Testing
The decision to order labs for acute asthma exacerbation should be based on the individual patient's presentation and clinical severity. For example:
- Patients with severe exacerbations, defined by symptoms such as severe dyspnea, wheezing, and decreased PEFR, may require more extensive lab testing, including ABG measurements and CBC 2, 3
- Patients with mild to moderate exacerbations may not require lab testing, and treatment can be guided by clinical assessment and response to initial therapy 4, 3
Additional Considerations
It is essential to note that the primary diagnosis of asthma is clinical, and lab testing should not delay treatment 5, 4. The focus should be on rapidly assessing the severity of the exacerbation and initiating appropriate treatment, including bronchodilators, corticosteroids, and supplemental oxygen as needed 2, 4, 3.