Acute Asthma

An acute exacerbation of asthma is characterised by a rapid deterioration in the symptoms of asthma. This could be triggered by any of the typical asthma triggers, such as infection, exercise or cold weather.



  • 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

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.



It is important to assess the severity of asthma to guide how aggressively they need to be treated. The table below is adapted from the BTS / SIGN guidelines from 2016.



Life Threatening

Peak flow > 50 % predicted

Peak flow < 50% predicted

Peak flow < 33% predicted

Normal speech

Saturations < 92%

Saturations < 92%

No features listed across

Unable to complete sentences in one breath

Exhaustion and poor respiratory effort

Signs of respiratory distress


Respiratory rate:

> 40 in 1-5 years

> 30 in > 5 years

Silent chest

Heart rate

> 140 in 1-5 years

> 125 in > 5 years


Altered consciousness / confusion



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)


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


Mild cases can be managed as an outpatient with regular salbutamol inhalers via a spacer (e.g. 4-6 puffs every 4 hours).


Moderate to severe cases require a stepwise approach working upwards until control is achieved:

  1. Salbutamol inhalers via a spacer device: starting with 10 puffs every 2 hours
  2. Nebulisers with salbutamol / ipratropium bromide
  3. Oral prednisone (e.g. 1mg per kg of body weight once a day for 3 days)
  4. IV hydrocortisone
  5. IV magnesium sulphate
  6. IV salbutamol
  7. 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.


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.

Consider monitoring the serum potassium when on high doses of salbutamol as it causes potassium to be absorbed from the blood into the cells.

It is also worth noting that salbutamol causes tachycardia and a tremor.



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


Last updated August 2019