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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Acute severe and life-threatening asthma

Respiratory · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Escalate

A silent chest, cyanosis, poor respiratory effort, exhaustion, altered consciousness, arrhythmia, hypotension, SpO2 below 92%, PEF below 33% best/predicted, PaO2 below 8 kPa, or normal/raised PaCO2 in a severe attack is life-threatening. Call senior and critical-care/anaesthetic help immediately while continuing treatment.

Synopsis

Grade an adult asthma attack objectively, deliver oxygen, bronchodilator and steroid treatment without delay, and escalate early when response or blood gases indicate life-threatening disease.

  • Treat first and assess in parallel: ABCDE, help, continuous monitoring, oxygen target 94-98%, bronchodilator and systemic corticosteroid.
  • Acute severe asthma is any of PEF 33-50%, respiratory rate at least 25/min, heart rate at least 110/min, or inability to complete sentences in one breath.
  • Life-threatening features include PEF below 33%, SpO2 below 92%, silent chest, cyanosis, poor effort, arrhythmia, hypotension, exhaustion or altered consciousness.
  • A normal PaCO2 is dangerous in a patient working hard to breathe; early attacks usually lower CO2, so normalisation can mean fatigue.
  • Initial nebulised salbutamol dose differs between current UK sources: the 2026 BTS/RCEM/SAM emergency pathway uses 2.5 mg, while the SIGN 158 acute algorithm uses 5 mg. Add ipratropium 500 micrograms in severe/life-threatening attacks and repeat or escalate according to response in a monitored emergency pathway.
  • Give prednisolone 40-50 mg orally promptly, or hydrocortisone 100 mg IV if oral treatment is not possible; oral is as effective when absorbed.
  • If inadequate response, use repeated or continuous salbutamol and consider IV magnesium sulfate 1.2-2 g over 20 minutes with senior oversight.
  • Do not sedate, do not rely on wheeze intensity, and do not delay ICU review for a chest radiograph.
  • Measure PEF before treatment if feasible without delay, then 15-30 minutes after and serially; record ability to speak, effort, SpO2, pulse and respiratory rate.
  • Discharge requires sustained clinical improvement, safe reliever spacing, ICS-containing maintenance, technique/action-plan review and prompt follow-up.

    • Key red flags

    Moderate attack

    Increasing symptoms with PEF above 50-75% best/predicted and no acute severe features. Still assess risk and response; prior near-fatal asthma lowers the admission threshold.

    Acute severe asthma

    Any one of PEF 33-50%, respiratory rate at least 25/min, pulse at least 110/min, or inability to complete sentences in one breath.

    Life-threatening asthma

    Any one of PEF below 33%, SpO2 below 92%, PaO2 below 8 kPa, normal PaCO2 4.6-6.0 kPa, silent chest, cyanosis, poor effort, arrhythmia, hypotension, exhaustion or altered consciousness.

    Near-fatal asthma

    Raised PaCO2 and/or need for mechanical ventilation. Involve critical care immediately; deterioration can be rapid and intubation is high risk.

    Complication or mimic

    Sudden unilateral signs, pleuritic pain, subcutaneous emphysema, fever/focal crepitations, urticaria/airway swelling or inspiratory stridor suggests pneumothorax, pneumonia, anaphylaxis or upper-airway obstruction.

    Investigation priorities

    01
    PEF percentage best or predictedFirst step

    Objectively grade airflow and response.

    Management branches

    First 10 minutesImmediate severe-attack bundle

    Any acute severe or life-threatening feature.

    1. Call senior help; use ABCDE, continuous SpO2/ECG, IV access and document PEF if possible without delaying treatment.
    2. Give oxygen to SpO2 94-98%. For initial nebulised salbutamol, the 2026 BTS/RCEM/SAM pathway specifies 2.5 mg and SIGN 158 specifies 5 mg; use the current adopted emergency pathway and document the source. Add ipratropium 500 micrograms nebulised in severe/life-threatening disease.
    3. Give prednisolone 40-50 mg orally immediately or hydrocortisone 100 mg IV if oral absorption/route is unsuitable.
    4. If life-threatening features exist, obtain ABG and involve ICU/anaesthetics now; do not wait to see whether the first nebuliser works.

    Key medicines

    SalbutamolInitial nebulised dose: 2.5 mg in the 2026 BTS/RCEM/SAM emergency pathway; 5 mg in the SIGN 158 acute algorithm. Repeat every 15-30 minutes if response is inadequate; monitored continuous nebulisation at 5-10 mg/hour may be used in refractory severe attacks. Spacer alternative: 4 puffs initially, then 2 puffs every 2 minutes up to 10 puffs.Monitor pulse, rhythm, potassium, glucose and lactate with repeated/high doses. Use air-driven nebuliser plus supplemental oxygen in hypercapnic-risk contexts when applicable; do not let delivery logistics delay treatment.
    Ipratropium bromide500 micrograms nebulised with the initial beta2 agonist in acute severe or life-threatening asthma; repeat according to the acute protocol, commonly every 4-6 hours once improving.Avoid aerosol in the eyes, especially with glaucoma; not a substitute for beta2 agonist or steroid and not required indefinitely after recovery.
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    Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
    Sources

    Sources and review status

    National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

    • BTS/SIGN British guideline on asthma—acute adult sectionsAdult severity criteria, emergency treatment and monitoring; chronic sections superseded by NG245.
    • BTS enhanced emergency assessment pathways for asthma and COPDJuly 2026 operational emergency-care resource.
    • BTS emergency oxygen guidelineAcute-asthma oxygen target 94-98%.
    • Atrovent 250 UDVs SmPCAdult acute-bronchospasm ipratropium dose.
    • NICE NG245 chronic asthma recommendationsPost-attack ICS-containing maintenance and action-plan context.

    Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

    Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom