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Asthma (Acute)

Asthma Pathway (BTS, NICE, SIGN) [SIGN 244]

Adult Guidelines

Severity Criteria
Moderate No features of severe acute asthma, and:
  • PEF >50-75% (best or predicted)
  • Increasing symptoms
Severe Any of the following:
  • PEF 33-50% (best or predicted)
  • Respiratory rate ≥25/min
  • Pulse ≥110/min
  • Inability to complete sentence in one breath
Life-threatening Any of the following:
  • PEF <33% (best or predicted)
  • SpO2 <92%
  • PaO2 <8 kPa
  • Normal PaCO2 (4.6-6.0 kPa) - indicates respiratory muscle fatigue
  • Low pH
 
  • Cyanosis
  • Exhaustion or altered conscious level
  • Arrhythmia or hypotension
  • Silent chest
Near-fatal Any of the following:
  • PaCO2 >6.0 kPa
  • Requiring mechanical ventilation with raised inflation pressures

Refer all the following severity to hospital:
  • Severe
  • Life-threatening asthma
  • Near-fatal

Admission criteria:
  • Life-threatening or near-fatal asthma attack
  • Severe features persist after initial treatment
  • Pregnant
  • Presentation at night
  • Asthma attack despite oral corticosteroid prior presentation
  • Previous near-fatal asthma attack

Offer all the following:
  • β2 agonist bronchodilator (e.g. salbutamol) via spacer
    • If no improvement → nebulised salbutamol 5mg (preferably oxygen-driven)
 
  • Prednisolone 40-50mg (continue for minimum 5 days)

Offer all the following:
  • Oxygen therapy - only if SpO2 <94%
 
  • Bronchodilator therapy 
    • Nebulised salbutamol 5mg (preferably oxygen-driven)
    • +/- Nebulised ipratropium 0.5mg (usually given routinely if life-threatening attack or add-on if poor response to salbutamol)
 
  • Steroid
    • Oral prednisolone 40-50mg daily (continue for minimum 5 days)
    • If cannot swallow oral tablet (e.g. due to vomiting) → IV hydrocortisone 400mg daily

The following should only be used after consultation with senior medical staff:
  • Magnesium sulfate 1.2-2g IV infusion over 20 min (single dose)
  • Amiophylline IV (no robust evidence)
  • IV salbutamol

Transfer to ICU for intubation is indicated if there is:
  • Hypercapnia
  • Falling pH or rising hydrogen on ABG
  • Persisting or worsening hypoxia
  • Exhaustion, altered conscious state
  • Poor respiratory effort or respiratory arrest

Measure the following to monitor treatment:
  • PEF
  • Pulse oximetry
  • Blood gas

There are no explicit guidance on when to discharge but the following should be met:
  • PEF >75% (best or predicted), and
  • On medical therapy that can be continued at home (i.e. oral tablets, inhalers) (no oxygen therapy, nebulisers, IV therapy etc.)

Actions to be preformed before discharing the patient:
  • Provide asthma education
    • Inhaler technique
    • PEF record keeping
    • Written PEF and symptom-based personalised asthma action plan
 
  • Follow up
    • With GP within 2 days
    • With respiratory clinic within 1 month

Children Guidelines

Essentially the same as adults, apart from age-specific heart rate and respiratory rate which has been removed for simplification.

The main difference is that SpO2 <92% puts the patient in the severe category (in adult, SpO2 <92% would put the patient in the life-threatening category)
 
Severity Criteria
Moderate No features of severe acute asthma, and:
  • PEF >50-75% (best or predicted)
  • Increasing symptoms
Severe Any of the following:
  • SpO2 <92%
  • PEF 33-50% (best or predicted)
  • Inability to complete sentence in one breath
Life-threatening SpO2 <92% + any of the following:
  • PEF <33% (best or predicted)
  • Silent chest
  • Poor respiratory effort
  • Confusion
  • Cyanosis
 

ALL patients:
  • β2 agonist bronchodilator (e.g. salbutamol) via spacer (1 puff every 60 sec up to maximum of 10 puffs)
    • If no improvement → nebulised salbutamol 5mg
  • Oral prednisolone 30-40mg daily (continue for minimum 5 days)

Offer all the following:
  • Oxygen therapy - only if SpO2 <94%
 
  • Bronchodilator therapy 
    • Nebulised salbutamol 5mg (preferably oxygen-driven)
    • +/- Nebulised ipratropium 0.5mg (usually given routinely if life-threatening attack or add-on if poor response to salbutamol)
 
  • Steroid
    • Oral prednisolone 30-40mg daily (continue for minimum 5 days)
    • If cannot swallow oral tablet (e.g. due to vomiting) → IV hydrocortisone 4mg/kg daily

Only consider the following after consulting specialist:
  • Magnesium sulfate (40mg/kg/day)
  • Amiophylline IV (no robust evidence)
  • IV salbutamol (no robust evidence)

References

Author: Adams Lau
Reviewer:
Last edited: 29/07/25