acute exacerbation of asthma
Written by Sarah Lee
Last Reviewed: April 2019
Review Due: April 2020
'an acute or subacute episode of progressive worsening of symptoms of asthma, including shortness of breath, wheezing, cough, and chest tightness'
The management of an acute asthma exacerbation is guided by the severity of the attack, as defined below.
PEF >50-75% of best/predicted
No signs of severe asthma
Severe (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
Life-Threatening (any one of the following):
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)
Poor respiratory effort
Altered conscious level
Near-Fatal (any one of the following):
Requiring mechanical ventilation with raised inflation pressures
Multiple factors may contribute to the onset of an acute exacerbation of asthma, including infection or exposure to allergens/precipitants.
SIGNS AND SYMPTOMS
Cough (often nocturnal)
Sputum Production (yellow)
Widespread wheeze on auscultation
1. Airway Inflammation
Exposure to allergen triggers an IgE-mediated Type 1 hypersensitivity reaction within the lungs.
Mast cell degranulation and production of inflammatory mediators (eg histamine, leukotrines) and cytokines (eg Il-4, IL-5) occurs.
Inflammatory cells including eosinophils migrate to airways produce more mediators, propagating the inflammatory response.
2. Airway Obstruction
Inflammation causes bronchospasm, mucosal oedema and increased mucus secretion within airways.
Chronic inflammation may cause bronchial smooth muscle hypertrophy and airway remodelling over time which may cause airflow limitations to be only partially reversible.
3. Bronchial Hyperresponsiveness
Eosinophil products increase resting tone of bronchial smooth muscle.
Bronchi become hyperresponsive and produce a larger response, more quickly to the allergen on the next exposure.
Peak Expiratory Flow (PEF)
With comparison to baseline
For evidence of infection
Arterial Blood Gas
To assess oxygenation and determine severity
For evidence of infection/pneumothorax
Oxygen to maintain saturations of 94-98%
Salbutamol/Terbutaline via oxygen driven nebuliser (can be given multiple times)
Ipratropium Bromide via oxygen driven nebuliser
IV Hydrocortisone or PO Prednisolone
If life-threatening features, consider infusion of IV Magnesium Sulphate
Ensure patient is monitored for signs of detioration, and consider prompt referral to HDU/ITU if severe or life-threatening features present
Before discharge from hospital, patients should:
Have been on discharge medication for 12-24 hours
Have inhaler technique checked
Be referred to the respiratory specialist nurse (for new diagnoses)
Have treatment with oral and inhaled steroids
Have their own peak flow meter
Arrange an appointment with their GP within 2 working days
Have a follow up appointment at the respiratory clinic within 4 weeks
Oxford Handbook of Clinical Medicine