Management of Acute Severe Asthma in Adults in Hospital

The flowchart below has been adapted for local use. The original flowchart is available at: Scottish Intercollegiate Guidelines Network (SIGN). British Guideline in the Management of Asthma. Edinburgh: SIGN; 2019 (SIGN publication no. 158), available from All changes in the flowchart below have been denoted by # and should not be taken as an endorsement by the original authors. 

Features of acute severe asthma:
  • Peak expiratory flow (PEF) 33–50% of best (use % predicted if recent best unknown).
  • Can't complete sentences in one breath.
  • Respiration >25breaths/minute.#
  • Pulse >110beats/minute.#
Life-threatening features:
  • PEF <33% of best or predicted.
  • SpO2 <92%
  • Silent chest, cyanosis, or feeble respiratory effort.
  • Arrhythmia or hypotension. 
  • Exhaustion, altered consciousness. 

If patient has any life-threatening feature:

Measure arterial blood gases. No other investigations are needed for immediate management.

Blood gas markers of a life-threatening attack:

  • Normal (4.6–6kPa, 35–45mmHg) PaCO2
  • Severe hypoxia: PaO2 <8kPa (60mmHg) irrespective of treatment with oxygen.
  • A low pH (or high H+).

Caution: Patients with severe or life-threatening attacks may not be distressed and may not have all these abnormalities. The presence of any should alert the doctor.

Near fatal asthma:
  • Raised PaCO2
  • Requiring mechanical ventilation with raised inflation pressures. 

  • Oxygen to maintain SpO2 94–98%. (CO2 retention is not usually aggravated by oxygen therapy in asthma).#
  • Salbutamol 5mg or terbutaline 10mg via an oxygen-driven nebuliser.#
  • Ipratropium bromide 0.5mg via an oxygen-driven nebuliser.
  • Prednisolone oral 40–50mg or hydrocortisone IV 100mg if unable to take oral.#
  • No sedatives of any kind.
  • Repeat chest radiograph only if pneumothorax or consolidation are suspected or patient requires mechanical ventilation.#
  • Discuss with senior clinician and ICU team.
  • Consider IV magnesium sulphate 1.2–2g infusion over 20 minutes (unless already given).
  • Give nebulised beta2 agonist more frequently e.g. salbutamol 5mg up to every 15–30 minutes or (if special nebuliser available for continuous nebulisation) 10mg/hour.#
  • Oxygen to maintain SpO2 94–98%.
  • Prednisolone oral 40–50mg each day or hydrocortisone IV 100mg 6 hourly.#
  • Nebulised beta2 agonist and ipratropium 4–6 hourly.#
  • Continue oxygen and steroids.
  • Use continuous nebulisation of salbutamol at 5-10mg/hour if specialist nebuliser available. Otherwise give nebulised salbutamol 5mg every 15–30 minutes.#
  • Continue ipratropium 0.5mg 4–6 hourly until patient is improving.
  • Discuss patient with senior clinician and ICU team.
  • Consider IV magnesium sulphate 1.2–2g over 20 minutes (unless already given).
  • Senior clinician may consider use of IV salbutamol or IV aminophylline (see Appendix 2 for details on preparation and administration) or progression to mechanical ventilation.#
  • Repeat measurement of PEF 15–30 minutes after starting treatment.
  • Oximetry: maintain SpO2 94–98%.#
  • Repeat blood gas measurements within 1 hour of starting treatment if:
    • initial PaO2 <8kpa (60mmHg) unless subsequent SpO2 >92% or
    • PaCO2 normal or raised or
    • patient deteriorates.
  • Chart PEF before and after giving beta2 agonists and 4 times daily during hospital stay.#

Transfer to ICU accompanied by doctor prepared to intubate if:

  • Deteriorating PEF, worsening or persisting hypoxia, or hypercapnia.
  • Exhaustion, altered consciousness
  • Poor respiratory effort or respiratory arrest.

When discharged from hospital, patients should have:

  • Been on discharge medication for 12-24 hours and have had inhaler technique checked and recorded.
  • Prior to discharge, been referred to the respiratory nurse specialists for education and inhaler technique if they have been admitted with a new diagnosis or exacerbation of asthma.#
  • PEF >75% of best or predicted and PEF diurnal variability <25% unless discharge is agreed with respiratory physician (for normal peak flow diagram see SIGN 158, Annex 5 in full asthma guideline).#
  • Treatment with oral (prednisolone 40-50mg until recovery - minimum of 5 days) and inhaled steroids in addition to bronchodilators. Patients should have inhaled corticosteroid therapy started if new diagnosis or treatment increased if poorly controlled prior to admission. This will usually be guided by respiratory nurses. For guidance on inhaler choice see the GGC Adult Asthma inhaler device guide.#
  • Own peak flow meter and written asthma action plan.#
  • GP follow up arranged within 2 working days.
  • Follow up appointment in respiratory clinic within 4 weeks.


Patients with severe asthma (indicated by need for admission) and adverse behavioural or psychosocial features are at risk of further severe or fatal attacks:

  • Determine reason(s) for exacerbation and admission.
  • Send details of admission, discharge and potential best peak expiratory flow rate to GP.#

Guideline reviewed: August 2022

Page last updated: September 2022