Asthma Exacerbation Flashcards
What is an asthma exacerbation?
An asthma exacerbation is an acute or subacute episode of progressive worsening of symptoms of asthma, including shortness of breath, wheezing, cough, and chest tightness. Exacerbations are marked by decreases from baseline in objective measures of pulmonary function, such as peak expiratory flow rate.
What are the risk factors for as asthma exacerbation?
- Viral infection
- Uncontrolled asthma symptoms
- High use of short-acting beta-2 agonists
- Inadequate use of inhaled corticosteroids
- Incorrect inhaler technique
- Smoking
- Exposure to allergens
- Exercise (especially in the cold)
- Obesity
- Air pollution
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What are the symptoms of an asthma exacerbation?
- Shortness of breath
- Chest tightness
- Cough
- Wheeze
What are the signs of an asthma exacerbation?
- Progressive decrease in lung function (measured by PEF)
- Tachypnoea
- Tachycardia
- Silent chest
- Accessory muscle use
Describe the characteristics of moderate acute asthma
- Increasing symptoms
- Peak flow > 50-75% best or predicted
- No features of acute severe asthma
Describe the characteristics of severe acute asthma
Any one of the following:
- Peak flow 33-50% best or predicted
- Respiratory rate ≥ 25/min
- Heart rate ≥ 110/min
- Inability to complete sentences in one breath
Describe the characteristics of life threatening acute asthma
Any one of the following, in a patient with severe asthma:
- Peak flow < 33% best or predicted
- Arterial oxygen saturation (SpO2) < 92%
- Partial arterial pressure of oxygen (PaO2) < 8 kPa
- Normal partial arterial pressure of carbon dioxide (PaCO2) (4.6–6.0 kPa)
- Silent chest
- Cyanosis
- Poor respiratory effort
- Arrhythmia
- Exhaustion
- Altered conscious level
- Hypotension
Describe the characteristics of near-fatal acute asthma
Raised PaCO2 and/or the need for mechanical ventilation with raised inflation pressures.
What investigations should be ordered for an asthma exacerbation?
- ABG
- Peak flow
- Pulse oximetry
- CXR
Why investigate ABG? And what may this show?
- Measure arterial oxygen saturations (SpO2). SpO2 <92% is associated with a risk of hypercapnia.
- Severe asthma: ‘normal’ or raised PaCO2 (>4.6 kPa), severe hypoxia (PaO2 <8 kPa) and low pH.
What are the SpO2 values that correspond to moderate, severe and life threatening asthma?
Moderate asthma: SpO2 ≥92%.
Acute severe asthma: SpO2 ≥92%.
Life-threatening asthma: SpO2 <92%.
Why investigate peak flow? And what may this show?
- Measure PEF to help assess severity and direct decisions about management. If possible refer back to patients baseline.
- Decrease in baseline.
What are the peak flow values that correspond to moderate, severe and life-threatening asthma?
- Moderate asthma: PEF 50%-75% of best or predicted
- Acute severe asthma: PEF 33%-50% of best or predicted
- Life-threatening asthma: PEF <33% of best or predicted
Why investigate pulse oximetry? And what may this show?
- Use pulse oximetry to determine the adequacy of oxygen therapy and the need for arterial blood gas measurement.
- Reducted SpO2.
Why investigate CXR? And what may this show?
- Only request a chest x-ray if there is:
- Suspected pneumomediastinum or pneumothorax
- Suspected pneumonia/consolidation
- Life-threatening asthma
- Failure to respond to treatment satisfactorily
- Requirement for ventilation.
- Often normal, even in a life-threatening exacerbation.
Briefly describe the treatment for a moderate acute asthma exacerbation
- Nebulised beta-2 agonists (i.e. salbutamol 5mg repeated as often as required)
- Nebulised ipratropium bromide
- Steroids
- Oral prednisolone or IV hydrocortisone
- These are continued for 5 days
- Antibiotics if there is convincing evidence of bacterial infection
Briefly describe the treatment for severe acute asthma exacerbation
- Oxygen if required to maintain sats 94-98%
- Aminophylline infusion
- Consider IV salbutamol
Briefly describe the treatment for life-threatening asthma exacerbation
- IV magnesium sulphate infusion
- Admission to HDU / ICU
- Intubation in worst cases
- However this decision should be made early because it is very difficult to intubate with severe bronchoconstriction
What is the rationale for oxygen in an asthma exacerbation?
Urgently give supplementary oxygen to hypoxaemic patients to maintain an oxygen saturation (SpO2) of 94% to 98%.
What is the first-line treatment in an all asthma exacerbations? And why?
High-dose inhaled beta-2 agonist (e.g. salbutamol) as a first-line agent as early as possible.
Inhaled beta-2 agonists act quickly and have few side-effects.
Briefly describe the mechanism of action of high-dose inhaled beta-2 agonists
Dilation of bronchial smooth muscle.
What is the corticosteroid of choice in the treatment of an asthma exacerbation?
Systemic corticosteroid such as prednisolone.
When is magnesium sulphate used in an acute asthma exacerbation?
Consider a single dose of intravenous magnesium sulfate for the patient with asthma with PEF <50% of best or predicted who has not responded well to initial inhaled bronchodilator therapy.
E.g. in life-threatening asthma.
When is aminophylline used in an acute asthma exacerbation?
Consider in patients with severe or life-threatening asthma who have had a poor response to initial therapy.
What differentials should be considered in an acute asthma exacerbation?
- Acute broncholitis
- Pneumonia
- Foreign body or obstruction
How does an acute asthma exacerbation and acute bronchiolitis differ?
- Differentiating signs and symptoms: may cause cough and wheeze, and lead to shortness of breath, with or without asthma. In practice, acute viral bronchiolitis is difficult to differentiate from a viral exacerbation of asthma.
- Differentiating investigations: diagnosis is clinical.
How does an acute asthma exacerbation and pneumonia differ?
- Differentiating signs and symptoms: signs and symptoms consistent with a lower respiratory tract infection (i.e., cough, dyspnoea, pleuritic chest pain, mucopurulent sputum, myalgia, fever) and no other explanation for the illness (e.g., sinusitis or asthma).
- Differentiating investigations: consolidation seen on CXR.
How does an acute asthma exacerbation and foreign body/ obstruction differ?
- Differentiating signs and symptoms: may cause a localised wheeze, depending on the site of obstruction. History may reveal a foreign body aspiration.
- Differentiating investigations: fibreoptic bronchoscopy is the definitive test for diagnosis and treatment of a foreign body in the airway.
How does an asthma exacerbation present on an ABG?
Initially patients will have a respiratory alkalosis as tachypnoea causes a drop in CO2.
A normal pCO2 or hypoxia is a concerning sign as it means they are tiring and indicates life threatening asthma.
A respiratory acidosis due to high CO2 is a very bad sign in asthma.
What monitoring is required for patients in an asthma exacerbation?
To monitor the response to treatment you can use:
- Respiratory rate
- Respiratory effort
- Peak flow
- Oxygen saturations
- Chest auscultation
What are some important things to note when giving a patient salbutamol?
Monitor serum potassium when on salbutamol as it causes potassium to be absorbed from the blood into the cells.
Salbutamol also causes tachycardia (fast heart rate).
