Status asthmaticus

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S. [2]

Overview

Status asthmaticus is an acute exacerbation of asthma that does not respond to standard bronchodilator and corticosteroid therapy. Symptoms include chest tightness, rapidly progressive dyspnea, non-productive cough and wheezing. Status asthmaticus if left untreated may result in severe bronchospasm, mucus plugging and rapidly develops acidosis and respiratory failure as a consequent of carbon di oxide retention and hypoxemia.

Epidemiology

Approximately 10% of the US population is affected by asthma with status asthmaticus requiring highest rates of hospitalization.

Predisposing factors

• Increase use of bronchodilator despite resistance,
• Frequent exacerbations despite the use of corticosteroids,
• Despite adhering to therapy, a peak flow rate of less than 10% from baseline,
• Frequent hospitalization for acute attacks,
• History of syncope or seizure during an acute asthmatic attack,
• Oxygen saturation lower than 92% despite supplemental oxygen,
• Airway obstruction is significantly reduced, resulting in severe impairment of air motion that leads to a silent chest with the absence of wheeze suggestive of an imminent respiratory arrest.

Diagnosis

History and Symptoms

• Rapidly progressive dyspnea
• Non-productive cough
• Profuse sweating
• Cyanosis
• Loss of consciousness and/or seizure secondary to severe hypoxia may be observed
• Inability to speak more than one or two words may be observed with severe airway obstruction

Physical Examination

Vital Signs

• Increased respiratory rate greater than 30 cycles per minute
• Increased heart rate
• Pulsus paradoxus (is a fall in SBP greater than 20-40 mmHg during inspiration)

General Physical Examination

• Sit upright with arms extended to support the upper chest (tripod position) that assist the use of accessory muscles of respiration
• Peak flow rate is a simple bedside measurement of airway obstruction and a red zone indicates less than 50% of the usual or normal peak flow reading signifying severe airway obstruction.

Respiratory Examination

Inspection

• Use of accessory muscles of respiration correlates with the disease severity
• Intercostal retractions
• Paradoxical thoraco-abdominal breathing

Auscultation

• High-pitch prolong polyphonic expiratory wheeze
• Bilateral crackles
• Air entry may or may not be reduced depending on the severity
• Absence of wheeze, breath sounds secondary to severe airway obstruction may represent a silent chest which is an ominous sign of imminent respiratory failure.

Cardiovascular Examination

Progressive untreated airway obstruction and increased work of breathing eventually leads to worsening hypoxemia, hypercarbia and increased air trapping with compromised stroke volume that results in bradycardia, hypotension, hypoventilation and subsequent cardiorespiratory arrest.

Neurological Examination

• Level of consciousness ranges from lethargy, agitation to even loss of consciousness or seizure, secondary to severe airway obstruction, hypoxia and carbon-di-oxide retention.
• Unable to speak in full sentences

Laboratory Tests

• Measurement of oxygen saturation by pulse oximetry may be useful to identify patients with acute severe asthma who may rapidly progress to respiratory failure and thereby require more intensive therapy.

• Arterial blood gas may reveal respiratory alkalosis that is consistent with the hypoxemia and/or hypercarbia secondary to significant hypoventilation.

• CBC count may demonstrate an increase in peripheral WBCs secondary to the use of steroids and β-agonists.

Pulmonary Function Test

FEV1 lower than 60% predicted is strongly suggestive of severe airway obstruction

ECG

The presence of supraventricular tachycardia on ECG should raise a suspicion of theophylline toxicity.

Imaging Modalities

High-resolution CT may reveal several structural changes related to small-airway disease including cylindrical bronchiectasis, bronchial wall thickening, and air trapping.

References

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