Which guideline covers acute asthma in the UK now?

The BTS/SIGN British guideline on the management of asthma, SIGN 158. NICE NG245, the joint BTS/NICE/SIGN guideline published in November 2024, states in its own overview that it does not cover managing acute asthma attacks, and the asthma pathway NICE NG244 has a 'Managing acute asthma' chapter whose content is a pointer to SIGN 158.

What counts as acute severe asthma in an adult?

Any one of a peak flow of 33 to 50% of best or predicted, a respiratory rate of 25 per minute or more, a heart rate of 110 per minute or more, or an inability to complete a sentence in one breath. Only one of the four is needed, which is why the observations have to be taken and read rather than glanced at.

What makes an asthma attack life-threatening?

On the criteria amended in 2025, a saturation below 92% plus any one of altered conscious level, exhaustion, arrhythmia, hypotension, cyanosis, silent chest or poor respiratory effort, or peak flow below 33% of best or predicted, PaO2 below 8 kPa, or a 'normal' PaCO2 of 4.6 to 6.0 kPa in a patient who already has severe asthma.

What dose of steroid is given in acute asthma?

Prednisolone 40 to 50 mg daily, or parenteral hydrocortisone 400 mg daily given as 100 mg six hourly. SIGN 158 says these are as effective as higher doses, that prednisolone should continue for at least five days or until recovery, and that the inhaled corticosteroid should not be stopped during the oral course.

Is magnesium given in acute asthma?

Nebulised magnesium sulphate is not recommended in adults. A single intravenous dose is considered in patients with acute severe asthma, meaning a peak flow below 50% of best or predicted, who have not had a good initial response to inhaled bronchodilators. The dose is 1.2 to 2 g as an infusion over 20 minutes, and SIGN 158 says it should only be used after consultation with senior medical staff.

When can a patient be discharged after an asthma attack?

SIGN 158 says no single physiological parameter defines the timing absolutely: the patient should have clinical signs compatible with home management, be on reducing amounts of beta2 agonist, and be on therapy they can continue safely. Patients discharged with a peak flow below 75% of best or predicted and diurnal variability above 25% are at greater risk of early relapse.

What follow-up is arranged after an admission with asthma?

Before discharge, SIGN 158 says to arrange follow-up with the patient's general practitioner or asthma nurse within two working days, and with a hospital specialist asthma nurse or respiratory physician at about one month after admission. It also says the primary care practice should be informed within 24 hours of discharge.

Acute Asthma — IMT Interview Clinical Station Answer

Acute asthma at the IMT (Internal Medicine Training) clinical station is answered by grading the attack before treating it. The BTS/SIGN British guideline on the management of asthma, SIGN 158, defines acute severe asthma in adults as any one of a peak flow of 33 to 50% of best or predicted, a respiratory rate of 25 per minute or more, a heart rate of 110 per minute or more, or inability to complete a sentence in one breath.

Key takeaways

NICE NG245, the BTS/NICE/SIGN asthma guideline, states that it does not cover acute asthma attacks; the asthma pathway NICE NG244 points to SIGN 158 for acute asthma, so SIGN 158 is the guideline to name.
Acute severe asthma in adults is any one of peak flow 33 to 50% of best or predicted, respiratory rate 25 per minute or more, heart rate 110 per minute or more, or inability to complete a sentence in one breath.
Life-threatening asthma, on the criteria amended in 2025, is oxygen saturation below 92% plus any one of altered conscious level, exhaustion, arrhythmia, hypotension, cyanosis, silent chest or poor respiratory effort, or peak flow below 33%, PaO2 below 8 kPa, or a normal PaCO2 of 4.6 to 6.0 kPa.
Oxygen is titrated to a saturation of 94% to 98%, and SIGN 158 asks for arterial blood gases in anyone with saturations below 92% or other life-threatening features.
Steroids go to every patient with an acute asthma attack: prednisolone 40 to 50 mg daily, or hydrocortisone 400 mg daily as 100 mg six hourly, continued for at least five days or until recovery.
Nebulised magnesium is not recommended in adults; a single intravenous dose of 1.2 to 2 g over 20 minutes is considered in acute severe asthma with a poor initial response, and only after discussion with senior medical staff.

How do you recognise acute asthma in the scenario?

Acute asthma is recognised from breathlessness, wheeze, cough and chest tightness in someone with known asthma, and graded from four measurements taken at the bedside rather than from how distressed they look.

SIGN 158 says clinical features alone are not specific, singly or together, and that their absence does not exclude a severe attack. Say that sentence, because it is the whole reason the severity table exists.

It also warns that pulsus paradoxus is an inadequate indicator of the severity of an attack and should not be used. In practice the silent chest and the exhausted patient are the ones candidates under-call.

What does the A to E assessment and the first hour look like?

The first hour of acute asthma is oxygen, a nebulised beta2 agonist and systemic steroid given together, with a peak flow and a set of observations taken as the grading measurement.

Oxygen: controlled supplementary oxygen to all hypoxaemic patients with acute severe asthma, titrated to a saturation of 94% to 98%, and not delayed for want of a pulse oximeter
Beta2 agonist: high-dose inhaled beta2 agonists as first-line agents, as early as possible, given by oxygen-driven nebulisation in acute severe or life-threatening asthma
Steroid: give steroids in adequate doses to all patients with an acute asthma attack, and the earlier the better
Ipratropium: add nebulised ipratropium bromide 0.5 mg four to six hourly for acute severe or life-threatening asthma, or a poor initial response to beta2 agonist alone
Measurements: peak flow as a percentage of the patient's previous best where known, saturations, respiratory rate, heart rate and the ability to complete a sentence

However, note the detail on repeat dosing. SIGN 158 says to repeat beta2 agonist doses at 15 to 30 minute intervals, or to give continuous nebulised salbutamol at 5 to 10 mg per hour with an appropriate nebuliser, if the response is inadequate.

Which investigations does acute asthma need?

Acute asthma needs a peak flow, pulse oximetry, and arterial blood gases only in defined circumstances. SIGN 158 asks for blood gases in patients with a saturation below 92%, whether on air or oxygen, or with other features of life-threatening asthma.

The reason it gives is worth quoting: a saturation below 92% is associated with a risk of hypercapnia, and hypercapnia is not detected by pulse oximetry.

A chest X-ray is not routine in acute asthma. SIGN 158 reserves it for suspected pneumomediastinum or pneumothorax, suspected consolidation, life-threatening asthma, failure to respond to treatment satisfactorily, and a requirement for ventilation.

What are the severity thresholds you must be able to say?

The severity table in acute asthma is the answer to most of the questions the panel will ask, so learn it as four bands rather than as a list of numbers.

Moderate acute asthma: increasing symptoms, peak flow above 50 to 75% of best or predicted, and no features of acute severe asthma
Acute severe asthma: any one of peak flow 33 to 50% of best or predicted, respiratory rate 25 per minute or more, heart rate 110 per minute or more, or inability to complete a sentence in one breath
Life-threatening asthma: a saturation below 92% plus any one of altered conscious level, exhaustion, arrhythmia, hypotension, cyanosis, silent chest or poor respiratory effort, or peak flow below 33% of best or predicted, PaO2 below 8 kPa, or a normal PaCO2 of 4.6 to 6.0 kPa
Near-fatal asthma: a raised PaCO2, or a requirement for mechanical ventilation with raised inflation pressures

In practice the sentence that marks out a strong candidate is about the normal carbon dioxide. In acute asthma a patient should be blowing it off, so a normal PaCO2 is a life-threatening feature, not reassurance.

What is the definitive management of acute asthma?

Definitive management of acute asthma is repeated beta2 agonist, systemic steroid continued for at least five days, ipratropium in the severe group, and escalation to magnesium or aminophylline only with senior agreement.

Prednisolone 40 to 50 mg daily, or parenteral hydrocortisone 400 mg daily given as 100 mg six hourly, which SIGN 158 says are as effective as higher doses
Continue prednisolone 40 to 50 mg daily for at least five days or until recovery if longer, and do not stop the inhaled corticosteroid while the oral course runs
Steroids can be stopped abruptly after recovery, without tapering, provided the patient is on an inhaled corticosteroid and has not been on maintenance steroid or three or more weeks of treatment
Nebulised magnesium sulphate is not recommended in adults with acute asthma; a single intravenous dose of 1.2 to 2 g over 20 minutes is considered in acute severe asthma with a peak flow below 50% and a poor initial response, only after consultation with senior medical staff
Intravenous aminophylline is used only after consultation with senior medical staff, at a loading dose of 5 mg per kilogram over 20 minutes unless the patient is on maintenance oral therapy, then 0.5 to 0.7 mg per kilogram per hour
If intravenous beta2 agonists are used, which SIGN 158 reserves for patients in whom inhaled therapy cannot be used reliably, consider monitoring the serum lactate for toxicity

When and to whom do you escalate acute asthma?

Escalate acute asthma to intensive care when the patient needs ventilatory support, or has acute severe or life-threatening asthma and is failing to respond to treatment.

Deteriorating peak flow
Persisting or worsening hypoxia
Hypercapnia
Arterial blood gas analysis showing a fall in pH or a rising hydrogen ion concentration
Exhaustion or feeble respiration
Drowsiness, confusion or an altered conscious state
Respiratory arrest

SIGN 158 also says that anyone transferred to intensive care should be accompanied by a doctor suitably equipped and skilled to intubate if needed. Say that, because it is a patient safety mark as much as a clinical one.

For admission, SIGN 158 says to admit any patient with a feature of life-threatening or near-fatal asthma, and any patient whose severe attack persists after initial treatment.

How do you hand over acute asthma in one minute?

The acute asthma handover uses SBAR with the severity grade and the peak flow percentage in the first sentence, because those decide whether the patient is admitted or watched.

Situation: a 27 year old with known asthma, peak flow 38% of best, respiratory rate 30, heart rate 124, unable to complete sentences. Background: two admissions this year, no previous intensive care.

Assessment: acute severe asthma, saturations 93% on 40% oxygen, no life-threatening features yet. Recommendation: back-to-back salbutamol with ipratropium given, prednisolone 40 mg given, please review in 15 minutes and confirm whether magnesium is needed.

What does the panel listen for in an acute asthma answer?

The panel listens for the severity grade named before treatment is described, the oxygen target of 94% to 98%, steroid for everyone, and the normal carbon dioxide recognised as a danger sign.

In practice they also mark the discharge plan, because SIGN 158 asks for follow-up with the general practitioner or asthma nurse within two working days and with a specialist at about one month. The internalmedicineinterview bank of 361 questions across 56 scenarios, with AI-marked spoken practice, is built to make that full arc a reflex.

What are the common mistakes in an acute asthma station?

Reassurance from a normal PaCO2, when it is a life-threatening criterion
Nebulised magnesium in an adult, which the guideline says is not recommended
Giving intravenous magnesium or aminophylline without saying that senior medical staff are consulted first
Stopping the inhaled corticosteroid while prescribing oral prednisolone
Ordering a routine chest X-ray rather than reserving it for the five named indications
Discharging without a written action plan, inhaler technique check, or follow-up within two working days

How this comes up at the IMT interview

Acute asthma maps onto all three parts of the IMT clinical station. Investigations and diagnosis is the peak flow, the saturations and the decision about blood gases; management is oxygen, beta2 agonist, steroid and ipratropium in the right order; and communication is explaining to a young patient why a normal-sounding chest is the reason you are calling intensive care.

The handover minute is where the severity grade, the peak flow percentage and the response to the first treatment get said with a time to review, which is exactly the sentence structure the station rewards.

Acute Asthma: The Severity Table, Oxygen Targets and Who Goes to Intensive Care