Status asthmaticus Flashcards
What are goals of management for status asthmaticus?
Management goals for status asthmaticus are (1) to reverse airway obstruction rapidly through the aggressive use of beta2-agonist agents and early use of corticosteroids, (2) to correct hypoxemia by monitoring and administering supplemental oxygen, and (3) to prevent or treat complications such as pneumothorax and respiratory arrest
What is status asthmaticus?
Status asthmaticus is considered a medical emergency. It is the extreme form of an asthma exacerbation that can result in hypoxemia, hypercarbia, and secondary respiratory failure. In practice, the role of the physician is to prevent this from happening through patient compliance with controller medications (eg, steroid inhalers) in an outpatient setting.
What are symptoms of status asthmaticus?
Patients report chest tightness, rapidly progressive shortness of breath, dry cough, and wheezing and may have increased their beta-agonist intake (either inhaled or nebulized) to as often as every few minutes
What is the clinical presentation of status asthmaticus?
Typically, patients present a few days after the onset of a viral respiratory illness, following exposure to a potent allergen or irritant, or after exercise in a cold environment. Frequently, patients have underused or have been underprescribed anti-inflammatory therapy. Illicit drug use may play a role in poor adherence to anti-inflammatory therapy.
What causes status asthmaticus?
Exposure to an allergen or trigger causes a characteristic form of airway inflammation in susceptible individuals, exemplified by mast cell degranulation, release of inflammatory mediators, infiltration by eosinophils, and activated T lymphocytes.
What are the 2 phases of the pathogenesis of status asthmaticus?
Physiologically, acute asthma has two components: an early, acute bronchospastic aspect marked by smooth muscle bronchoconstriction and a later inflammatory component resulting in airway swelling and edema.
What is the role of the immune system in the pathogenesis of status asthmaticus?
Within minutes of exposure to an allergen, mast cell degranulation is observed along with the release of inflammatory mediators, including histamine, prostaglandin D2, and leukotriene C4. These substances cause airway smooth muscle contraction, increased capillary permeability, mucus secretion, and activation of neuronal reflexes. The early asthmatic response is characterized by bronchoconstriction that is generally responsive to bronchodilators, such as beta2-agonist agents.
What causes increased airway resistance and obstruction in the pathogenesis of status asthmaticus?
Bronchospasm, mucus plugging, and edema in the peripheral airways result in increased airway resistance and obstruction. Air trapping results in lung hyperinflation, ventilation/perfusion (V/Q) mismatch, and increased dead space ventilation. The lung becomes inflated near the end-inspiratory end of the pulmonary compliance curve, with decreased compliance and increased work of breathing.
The increased pleural and intra-alveolar pressures that result from obstruction and hyperinflation, together with the mechanical forces of the distended alveoli, eventually lead to a decrease in alveolar perfusion. The combination of atelectasis and decreased perfusion leads to V/Q mismatch within lung units. The V/Q mismatch and resultant hypoxemia trigger an increase in minute ventilation.
What does the absence of wheezing suggest in status asthmaticus?
Determine whether the patient has a severe asthma exacerbation without wheezing (ie, the silent chest). Such patients may have such severe airway obstruction or be so fatigued that they are unable to generate enough airflow to wheeze. This is an ominous sign of impending respiratory failure.
What is the progression of consciousness in patients with status asthmaticus?
The patient’s level of consciousness may progress from lethargy to agitation, air hunger, and even syncope and seizures. If untreated, prolonged airway obstruction and marked increase in the work of breathing may eventually lead to bradycardia, hypoventilation, and even cardiorespiratory arrest.
What are the initial physical findings in status asthmaticus?
Patients are usually tachypneic upon examination and, in the early stages of status asthmaticus, may have significant wheezing. Initially, wheezing is heard only during expiration, but wheezing later occurs during expiration and inspiration.
The chest is hyperexpanded, and accessory muscles, particularly the sternocleidomastoid, scalene, and intercostal muscles, are used. Later, as bronchoconstriction worsens, the wheezing may disappear, which may indicate severe airflow obstruction.
Which physical findings are characteristic of later stages of status asthmaticus?
An inability to speak more than one or two words at a time may also be observed in the later stages of an acute asthma episode. Ventilation/perfusion mismatch results in decreased oxygen saturation and hypoxia. Vital signs may show tachycardia and hypertension. The peak flow rate should be included in the vital signs in patients who are able to cooperate and who are able to tolerate the peak flow maneuver without significant distress.
What is the role of peak flow rate in the evaluation of status asthmaticus?
The peak flow rate is a standard measure of airflow obstruction and is relatively simple to perform. Most patients with more than a mild exacerbation of asthma have hypoxia and decreased oxygen saturation due to V/Q mismatch. Oxygen saturation may increase following the use of bronchodilators secondary to an increase in V/Q mismatch. Some patients prefer to remain seated and leaning forward, rather than assuming a supine position.
What is the significance of a finding retractions and abdominal muscle usage in status asthmaticus?
Retractions (ie, intercostal and subcostal) and the use of abdominal muscles may be observed in patients with status asthmaticus. The use of accessory muscles has been shown to correlate with the severity of airflow obstruction. An abnormally prolonged expiratory phase with audible wheezing can be observed. Patients with moderate to severe asthma are often unable to speak in full sentences.
What are cardiovascular symptoms of status asthmaticus?
Cardiovascular symptoms may include tachycardia or hypertension in mild to moderate asthma. With worsening hypoxemia, hypercarbia, marked air trapping, and hyperinflation, the ventricular stroke volume is compromised and hypotension and bradycardia may be observed.
