Asthma (Acute) Flashcards
What is acute asthma?
An acute exacerbation of asthma is characterised by a rapid deterioration in the symptoms of asthma.
Briefly describe the pathophysiology of an acute asthma exacerbation
Acute exacerbations of asthma in children can be triggered by exposure to allergens such as dust, pollution, animal hair or smoke, causing an IgE type 1 hypersensitivity reaction, leading to smooth muscle contraction, bronchial oedema and mucus plugging.
How may an asthma exacerbation present in a child?
- Progressively worsening shortness of breath
- Signs of respiratory distress
- Fast respiratory rate (tachypnoea)
- Expiratory wheeze on auscultation heard throughout the chest
- The chest can sound “tight” on auscultation, with reduced air entry
What are the signs of respiatory distress?
- Raised respiratory rate
- Use of accessory muscles of breathing, such as the sternocleidomastoid, abdominal and intercostal muscles
- Intercostal and subcostal recessions
- Nasal flaring
- Head bobbing
- Tracheal tugging
- Cyanosis (due to low oxygen saturation)
- Abnormal airway noises
Briefly describe the significance of a silent chest in an asthma exacerbation
A silent chest is an ominous sign. This is where the airways are so tight it is not possible for the child to move enough air through the airways to create a wheeze. This might be associated with reduce respiratory effort due to fatigue. A less experienced practitioner may think because there is no respiratory distress and no wheeze the child is not as unwell, however in reality this a silent chest is life threatening.
What are the features of a moderate asthma exacerbation?
- Peak flow > 50 % predicted
- Normal speech
- No features indicating severe or life-threatening
What are the features of a severe asthma exacerbation?
- Peak flow < 50% predicted
- Saturations <92%
- Unable to complete sentences in one breath
- Signs of respiratory distress
- Respiratory rate:
- > 40 in 1-5 years
- > 30 in > 5 years
- Heart rate:
- > 140 in 1-5 years
- > 125 in > 5 years
What are the features of a life-threatening asthma exacerbation?
- Peak flow < 33% predicted
- Saturations <92%
- Exhaustion and poor respiratory effort
- Hypotension
- Silent chest
- Cyanosis
- Altered consciousness and confusion
What differentials should be considered for an acute asthma exacerbation?
- Pneumothorax
- Anaphylaxis
- Inhalation of a foreign body
- Cardiac arrhythmia
Briefly describe the management of acute viral induced wheeze and asthma
Staples of management in acute viral induced wheeze or asthma are:
- Supplementary oxygen if required (i.e. oxygen saturations less than 94% or working hard)
- Bronchodilators (e.g. salbutamol, ipratropium and magnesium sulphate)
- Steroids to reduce airway inflammation: prednisone (orally) or hydrocortisone (intravenous)
- Antibiotics only if a bacterial cause is suspected (e.g. amoxicillin or erythromycin)
Briefly describe the step up management of bronchodilators
Bronchodilators are stepped up as required:
- Inhaled or nebulised salbutamol (a beta-2 agonist)
- Inhaled or nebulised ipratropium bromide (an anti-muscarinic)
- IV magnesium sulphate
- IV aminophylline
Briefly describe the management of mild acute asthma exacerbations
Mild cases can be managed as an outpatient with regular salbutamol inhalers via a spacer (e.g. 4-6 puffs every 4 hours).
Briefly describe the management of moderate and severe asthma exacerbations
Moderate to severe cases require a stepwise approach working upwards until control is achieved:
- Salbutamol inhalers via a spacer device: starting with 10 puffs every 2 hours
- Nebulisers with salbutamol / ipratropium bromide
- Oral prednisone (e.g. 1mg per kg of body weight once a day for 3 days)
- IV hydrocortisone
- IV magnesium sulphate
- IV salbutamol
- IV aminophylline
If you haven’t got control by this point the situation is very serious. Call an anaesthetist and the intensive care unit. They may need intubation and ventilation. This call should be made earlier to give the best chance of successfully intubating them before the airway becomes too constricted.
Briefly describe the stepdown following control of an asthma exacerbation
Once control is established you can gradually work your way back down the ladder as they get better:
- Review the child prior to the next dose of their bronchodilator
- Look for evidence of cyanosis (central or peripheral), tracheal tug, subcostal recessions, hypoxia, tachypnoea or wheeze on auscultation
- If they look well, consider stepping down the number and frequency of the intervention
- A typical step down regime of inhaled salbutamol is 10 puffs 2 hourly then 10 puffs 4 hourly then 6 puffs 4 hourly then 4 puffs 6 hourly
Briefly describe the discharge required following an acute asthma exacerbation
Generally, discharge can be considered when the child well on 6 puffs 4 hourly of salbutamol. They can be prescribed a reducing regime of salbutamol to continue at home, for example 6 puffs 4 hourly for 48 hours then 4 puffs 6 hourly for 48 hours then 2-4 puffs as required.
A few other steps to consider:
- Finish the course of steroids if these were started (typically 3 days total)
- Provide safety-net information about when to return to hospital or seek help
- Provide an individualised written asthma action plan
