Acute Asthma Attack

Triggers for an attack

  • Respiratory infection
  • Allergens
  • Airborne irritants
  • Air temperature change (particularly hot to cold)
  • Exercise
  • Emotional factors (e.g. laughing/stress/hyperventilation)
  • GORD
  • Drugs (NSAIDs/Beta blockers)
  • Foods


  • Severe breathlessness; tachypnoea; tachycardia
  • In severe cases there are other features (see below)
  • Patients should have PEFR (or FEV1) measured where appropriate; Pulse oximetry is important in all patients
  • Blood gases and CXR may be appropriate in acute severe or life-threatening exacerbations


  • Moderate
    • Increasing symptoms 
    • PEF >50-75% best or predicted
    • No features of acute severe
  • Acute severe
    • Any one of:
      • PEFR 33-50% best or predicted best
      • Respiratory rate >=25bpm and heart rate >= 110bpm
      • Inability to complete sentences in one breath
  • Life-threatening
    • Any one of
      • PEFR <33% best/predicted best
      • SpO2 <92%
      • PaO2 <8kPa
      • normal PaCO2 (i.e. 4.6-6kPa)
        • usually low PaCO2 in an exacerbation; if normal this could be a sign of deterioration; if high, this could be near fatal
      • silent chest
      • cyanosis
      • poor respiratory effort
      • arrhythmia
      • exhaustion, altered conscious level
  • Criteria for admission
    • Any patient with life-threatening features or those who could require assisted ventilation
    • Any patient with an acute severe attack which persists after initial treatment
    • Any child who does not respond to 10 puffs (2 puffs every 2 minutes) of beta-agonists
  • Criteria for discharge
    • If a patient is well and PEFR >75% after one hour of initial treatment (unless other reason for admission)



  • ABCDE approach is important.  Where an asthma exacerbation is likely, include the following at the appropriate steps
  • Oxygen therapy
  • Inhaled high dose Beta-agonists (nebulised with oxygen is recommended but not essential)
    • Add nebulised ipratropium bromide in acute severe/life-threatening asthma or those with a poor response to beta-agonists
    • In children a single dose of IV salbutamol may be considered if there is no response to inhaled agonists
  • Consider a single dose of IV magnesium sulphate for patients with acute severe asthma who do not respond or in all cases of life-threatening/near fatal asthma
  • Steroids – NB Give in all cases of acute asthma
    • Give early in children (20mg 2-5 years; 30-40mg in >5 years)
      • Consider IV steroids if required in children
    • Continue 40-50mg for 5 days after (or until full recovery)
  • If patient continues to decline or makes no improvement with life-threatening asthma, referral to ICU may be required

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