Acute severe asthma
A severe asthma attack unresponsive to standard bronchodilator and corticosteroid treatment.
Acute severe asthma, also called status asthmaticus, is a sudden worsening of asthma that fails to improve with standard treatments like inhalers and steroids. This condition involves a life-threatening blockage of the airways and requires emergency medical care, as it can lead to cardiac or respiratory arrest.
**Signs and symptoms** An asthma attack feels like a worsening of usual symptoms, with breathlessness and cough that often get worse at night. In acute severe asthma, shortness of breath can become so intense that a person cannot speak more than a few words or finish a sentence. During a physical exam, the breathing rate may be faster than 25 breaths per minute, and the heart rate may be 110 beats per minute or higher. Oxygen levels in the blood are often low but still above 92%. Listening to the lungs with a stethoscope may show reduced airflow or widespread wheezing. A bedside test called peak expiratory flow measures how fast air can be exhaled; in acute severe asthma, this flow is less than 50% of the person’s normal or predicted value. In very severe, near-fatal asthma, peak flow drops below 33% of predicted, oxygen saturation falls below 92%, or the lips turn blue (cyanosis). The chest may become silent—no wheezing is heard because too little air moves to produce it. Breathing effort decreases, and the person appears exhausted or drowsy. Irregular heartbeats and abnormally low blood pressure may also occur. Other symptoms include shortness of breath, inability to speak in full sentences, breathlessness even when lying down, chest tightness, a bluish tint to the lips, hunched shoulders, strained neck and stomach muscles, and a need to sit or stand up to breathe more easily.
**Cause** Experts do not know exactly what causes acute severe asthma attacks or why they do not respond to typical treatments. Factors that may contribute include not seeing a doctor regularly, poor asthma control, exposure to asthma triggers, allergies or severe allergic reactions, not using a peak flow meter or taking medication as prescribed, not following an asthma action plan, respiratory infections, severe stress, cold weather, air pollution, chemicals or other irritants, and smoking.
**Mechanism** In asthma, inflammation involves an early phase with an influx of eosinophils and a later phase with a mix of eosinophils, mast cells, lymphocytes, and neutrophils. The al
- field
- Medicine (respiratory disease)
- known_for
- Life-threatening asthma exacerbation unresponsive to standard therapy
- symptoms
- Chest tightness, rapidly progressive dyspnea, dry cough, use of accessory respiratory muscles, extreme wheezing
- complications
- Cardiac and/or respiratory arrest
- peak_flow_criteria
- Less than 50% of normal or predicted flow
Lore & Background
Acute severe asthma is characterized by symptoms such as chest tightness, rapidly progressive shortness of breath, dry cough, use of accessory respiratory muscles, and extreme wheezing. Breathlessness may be so severe that speaking more than a few words becomes impossible. On examination, respiratory rate may exceed 25 breaths per minute, heart rate may be 110 beats per minute or faster, and oxygen saturation may be reduced but above 92%. Peak expiratory flow is less than 50% of a person's normal or predicted flow.
Very severe acute asthma, termed near-fatal, is marked by peak flow less than 33% predicted, oxygen saturations below 92% or cyanosis, a silent chest (no audible wheezing), reduced respiratory effort, and visible exhaustion or drowsiness. Irregular heartbeat and abnormal lowering of blood pressure may occur. The cause of acute severe asthma attacks remains unknown, and experts are unsure why it does not respond to typical asthma treatments.
Treatment begins with first-line therapies such as short-acting beta agonists and oxygen, then advances to intravenous medications like magnesium sulfate, aerosolized bronchodilators, and positive-pressure therapy including mechanical ventilation. Intravenous corticosteroids and methylxanthines are often given. In mechanically ventilated patients, sedating medications such as ketamine or propofol may provide bronchodilating effects.
Reader's Guide
Acute severe asthma represents a critical medical emergency requiring immediate intervention. Its significance lies in its resistance to standard asthma treatments, making it a distinct and dangerous form of exacerbation. The condition's pathophysiology involves airway obstruction from smooth muscle constriction, edema, inflammatory cell influx, and mucus secretion, leading to impaired gas exchange and low blood oxygen levels. Diagnosis relies on clinical assessment, peak expiratory flow measurement, and oxygen saturation monitoring. Differential diagnoses include conditions such as congestive heart failure, chronic obstructive pulmonary disease, and vocal cord dysfunction, which can mimic status asthmaticus. The increasing prevalence of atopy and asthma remains unexplained but may be linked to respiratory virus infections. Epidemiology shows status asthmaticus is slightly more common in males and among people of African and Hispanic origin, with the gene locus glutathione dependent S-nitrosoglutathione (GSNOR) suggested as a possible correlation. Recent research explores interactions between airway epithelial cells and respiratory viruses, as well as the role of Type I interferon-driven upregulation of IgE receptors on dendritic cells in viral-induced atopic disease. The condition's legacy underscores the need for improved understanding of its mechanisms and more effective treatments.
Did You Know?
- Acute severe asthma is also known as status asthmaticus.
- It does not respond to standard treatments of bronchodilators and corticosteroids.
- Peak expiratory flow in acute severe asthma is less than 50% of a person's normal or predicted flow.
- Near-fatal asthma is characterized by a silent chest, oxygen saturations below 92%, and peak flow less than 33% predicted.
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