The patient is tachypneic and unable to speak in full sentences. Examination reveals prolonged expiration and prominent bilateral wheezing. Heart sounds are normal. Chest imaging shows a normal-sized heart and hyperinflated lungs with a flattened diaphragm. Bedside echocardiogram reveals no intrapericardial fluid accumulation or pericardial thickening. Which of the following physiologic changes is most likely to provide immediate relief in this patient?

Question

The patient is tachypneic and unable to speak in full sentences.  Examination reveals prolonged expiration and prominent bilateral wheezing.  Heart sounds are normal.  Chest imaging shows a normal-sized heart and hyperinflated lungs with a flattened diaphragm.  Bedside echocardiogram reveals no intrapericardial fluid accumulation or pericardial thickening.  Which of the following physiologic changes is most likely to provide immediate relief in this patient?

Quizplus · Accepted Answer

This patient's presentation with dyspnea, tachypnea, prolonged expiration, and bilateral wheezing is suggestive of acute exacerbation of obstructive pulmonary disease (asthma or COPD). Acute obstructive pulmonary exacerbations are primarily treated with beta-adrenergic agonists, which produce relaxation of bronchial smooth muscle by stimulating the beta-2-adrenergic receptor. This receptor is a G_S protein-coupled receptor that activates adenylyl cyclase and increases intracellular cAMP concentrations. Asthma and COPD exacerbation are the most frequent causes of pulsus paradoxus in the absence of significant pericardial disease (pericardial effusion or constrictive pericarditis). There is a small normal variation in intrathoracic pressure with respiration, which drops 2-5 mm Hg below the atmospheric pressure during inspiration. In patients with severe asthma or COPD exacerbation, this drop in intrathoracic pressure becomes greatly exaggerated and is transmitted to extrathoracic structures. This leads to an excessive drop in blood pressure with inspiration that is detected as pulsus paradoxus. (Choice B) Cromolyn sodium inhibits mast cell degranulation and release of histamine and leukotrienes. It is used occasionally for management of chronic asthma but is not effective for immediate relief of acute asthmatic or COPD exacerbations. (Choice C) Eosinophil degranulation would be impaired by corticosteroids, which play an important role in treatment of acute asthma or COPD exacerbations. However, beta agonists provide immediate relief, whereas corticosteroids would take several hours to a few days to take effect. (Choice D) Histamine is one of several mediators released in response to a hypersensitivity reaction that can lead to bronchial smooth muscle contraction. However, antihistamine therapy is not an effective treatment for asthma or COPD exacerbation. (Choice E) Calcium channel agonists are not used in acute treatment of asthma or COPD exacerbation. On the contrary, increased calcium influx could potentially worsen bronchial smooth muscle contraction. Educational objective: Asthma and chronic obstructive pulmonary disease (COPD) exacerbation are the most frequent causes of pulsus paradoxus in the absence of significant pericardial disease. Beta-adrenergic agonists control acute asthma and COPD exacerbations by causing bronchial smooth muscle relaxation via increased intracellular cAMP. __________ References: Effects of antihistamines in adult asthma: a meta-analysis of clinical trials. (http://www.ncbi.nlm.nih.gov/pubmed/9387943) Management of an acute asthma attack. (http://www.ncbi.nlm.nih.gov/pubmed/15999162) Mechanisms of pulsus paradoxus during resistive respiratory loading and asthma. (http://www.ncbi.nlm.nih.gov/pubmed/3745698)

The Patient Is Tachypneic and Unable to Speak in Full