Summary

Acute severe asthma is a medical emergency characterised by progressive bronchospasm, airway inflammation, and mucus hypersecretion leading to rapid respiratory deterioration. It remains a significant cause of preventable death, with approximately 3 deaths per day in the UK from asthma. The hallmark of management is early recognition of severity, aggressive bronchodilator therapy, systemic corticosteroids, and escalation to ICU when indicated.

Key Facts

• Incidence: ~100,000 hospital admissions/year in the UK; 1,500+ deaths annually
• Peak-flow: PEF <50% predicted indicates severe; <33% is life-threatening
• Golden hour: Steroids given within 1 hour reduce admission rates by 25%
• Magnesium: IV MgSO₄ reduces admissions in severe/life-threatening cases (NNT ~7)
• Silent chest: Most dangerous sign — indicates minimal air movement
• Avoid sedation: Never sedate a deteriorating asthmatic (risk of respiratory arrest)

Clinical Pearls

O SHIT M — Oxygen, Salbutamol, Hydrocortisone (or pred), Ipratropium, Theophylline, Magnesium

A "normal" or rising pCO₂ in acute asthma is a sign of impending respiratory failure (patient is tiring)

Always check inhaler technique before discharge — poor technique is the commonest cause of "brittle asthma"

Why This Matters Clinically

Acute asthma represents a unique window where rapid, protocolised intervention dramatically alters outcomes. Unlike many emergencies, the difference between good and bad outcomes is often measured in minutes. Junior doctors must be confident to escalate early when life-threatening features are present.

Immediate Management: O SHIT M (First 15 mins)

Must be started immediately on arrival:

1. Oxygen

   • High flow 15L/min via non-rebreathe mask
   • Target SpO₂ 94-98%
   • Do NOT withhold oxygen for fear of CO₂ retention (this is COPD)

2. Salbutamol

   • Nebulised 5mg oxygen-driven (6-8 L/min)
   • Repeat every 15-30 mins if needed
   • Consider back-to-back nebs in severe/life-threatening

3. Hydrocortisone / Prednisolone

   • Prednisolone 40-50mg PO if able to swallow
   • OR Hydrocortisone 100mg IV if vomiting/severe
   • Continue pred 40mg OD for 5-7 days

4. Ipratropium Bromide

   • 0.5mg nebulised with salbutamol
   • Add early in severe/life-threatening
   • Repeat every 4-6 hours

5. Theophylline (Aminophylline)

   • Consider if no response to above
   • Senior decision — narrow therapeutic window
   • Loading 5mg/kg over 20 mins (if not on maintenance)

6. Magnesium Sulphate

   • 2g IV over 20 mins in severe/life-threatening
   • Single dose; no evidence for repeat dosing
   • Works within 15-30 mins

[!WARNING] Do not delay steroids — oral is as effective as IV if the patient can swallow. The earlier given, the greater the benefit.

History (Focused)

• Onset: Rapid (hours) vs Gradual (days)?
• Triggers: URTI, allergen, exercise, weather, stress, medications?
• Severity markers: Previous ICU admission? Intubation? Frequent courses of steroids?
• Medications: Current preventer compliance? Inhaler technique?
• Red flags: Confusion, inability to speak, exhaustion

Examination Findings

Inspection:

• Posture (sitting forward, tripod position)
• Respiratory rate (>25 = severe)
• Accessory muscle use (SCM, intercostals)
• Cyanosis (late sign)
• Ability to speak (sentences → words → silent)

Auscultation:

• Widespread polyphonic wheeze (expiratory > inspiratory)
• Silent chest = critical (minimal air entry)
• Localised wheeze → consider alternative diagnosis (mucus plug, foreign body)

Palpation:

• Hyperresonant percussion
• Tracheal tug (severe)

BTS/SIGN Severity Classification

[!NOTE] One life-threatening feature = treat as life-threatening asthma

BTS/SIGN Severity Classification (UK Standard)

This classification guides management intensity and disposition:

Severe Features (Any ONE = Severe)

• PEF 33-50% best or predicted
• Respiratory rate ≥25/min
• Heart rate ≥110/min
• Inability to complete sentences in one breath

Life-Threatening Features (Any ONE = Life-Threatening)

• PEF <33% best or predicted
• SpO₂ <92%
• Normal or raised pCO₂ (4.6-6.0 kPa)
• Silent chest
• Cyanosis
• Poor respiratory effort
• Altered consciousness
• Exhaustion
• Arrhythmia / Hypotension

Treatment Pathway by Severity

Moderate Exacerbation:

1. Salbutamol 5mg neb (can use MDI + spacer: 10 puffs)
2. Prednisolone 40mg PO
3. Reassess at 15-30 mins
4. If PEF >75% and stable → consider discharge with pred course

Severe Exacerbation:

1. Oxygen 15L NRB mask
2. Salbutamol 5mg neb (oxygen-driven) — repeat PRN
3. Ipratropium 0.5mg neb
4. Prednisolone 40-50mg PO or Hydrocortisone 100mg IV
5. Admit for observation
6. Consider MgSO₄ 2g IV if no response

Life-Threatening:

1. Call for senior help / ICU outreach
2. High-flow O₂ 15L NRB
3. Back-to-back salbutamol nebs (continuous)
4. Ipratropium 0.5mg neb
5. Hydrocortisone 100mg IV (or pred if can swallow)
6. MgSO₄ 2g IV over 20 mins
7. Prepare for intubation if deteriorating

Near-Fatal / Failing Patient:

• ICU admission
• NIV (controversial — limited evidence, risk of delay)
• Intubation and ventilation
• IV Salbutamol (15mcg/min, up to 20mcg/min)
• IV Aminophylline (5mg/kg loading if not on theophylline)
• Consider IV Ketamine (bronchodilator properties)

Disposition Criteria

Safe for Discharge:

• PEF >75% predicted at 1 hour
• Stable on room air (SpO₂ >94%)
• Able to use inhalers correctly
• Written asthma action plan provided
• Prednisolone course prescribed (40mg x 5-7 days)
• Follow-up within 48 hours (GP) and 4 weeks (asthma clinic)

Admit if:

• PEF <75% at 1 hour
• Any life-threatening features
• Previous near-fatal attack
• Nocturnal exacerbation
• Pregnancy
• Social concerns / poor inhaler technique

Survival Statistics

• Overall mortality: 0.1-0.2% of acute presentations
• ICU mortality: 5-10% of intubated patients
• Post-near-fatal: 10% risk of death within 12 months if poorly controlled

Good Prognostic Factors

• Rapid response to initial bronchodilators (PEF >50% at 30 mins)
• Good inhaler technique
• Written asthma action plan
• Regular preventer use
• Never smoked
• No prior ICU admission

Poor Prognostic Factors

• Previous near-fatal attack
• Psychosocial dysfunction (denial, depression)
• Frequent oral steroid courses
• ≥3 ED visits per year
• Poor medication adherence
• Obesity
• Active smoking

Follow-Up Requirements

• 48-72 hours: GP review
• 4 weeks: Asthma specialist/nurse review
• Ongoing: Asthma action plan, annual flu vaccination, inhaler technique checks

Key Guidelines

1. BTS/SIGN British Guideline on the Management of Asthma (2019) — UK standard of care. brit-thoracic.org.uk
2. GINA Global Strategy for Asthma Management (2024) — International evidence synthesis. ginasthma.org
3. NICE NG80: Asthma (2021) — Commissioning guidance and quality standards.

Landmark Trials

3Mg Trial (2014) — IV Magnesium in severe acute asthma

• Population: 1,109 adults with severe asthma (PEF <50%)
• Intervention: 2g IV MgSO₄ vs placebo
• Outcome: 10% absolute reduction in hospital admission (NNT 10)
• Take-home: Use MgSO₄ early in severe/life-threatening cases

SMART Programme — Symbicort Maintenance and Reliever Therapy

• Demonstrates that single low-dose ICS-formoterol inhaler reduces exacerbations vs SABA alone
• Now recommended as preferred reliever in mild-moderate asthma (GINA 2024)

Evidence Strength by Intervention

What is an Asthma Attack?

An asthma attack happens when your airways suddenly become very narrow and inflamed. This makes it hard to breathe. You may feel:

• Very short of breath
• Tightness in your chest
• Wheezing (a whistling sound when you breathe)
• Unable to speak in full sentences
• Frightened or anxious

What Causes an Attack?

Common triggers include:

• Colds and chest infections (most common)
• Allergies (pollen, dust mites, pets)
• Cold air or weather changes
• Exercise
• Stress
• Smoke or strong smells
• Some medications (like ibuprofen for some people)

What Should I Do in an Attack?

1. Sit up — don't lie down
2. Take your blue reliever inhaler — 1 puff every 30-60 seconds, up to 10 puffs
3. If you're not better after 10 puffs, or you feel worse, call 999
4. If the ambulance hasn't arrived in 15 minutes, repeat 10 puffs

Warning Signs to Call 999

• You can't speak in full sentences
• Your lips or fingernails are turning blue
• Your blue inhaler isn't helping
• You feel exhausted or confused
• You're getting worse despite treatment

After Your Hospital Visit

You will be given:

• Steroid tablets to take for 5-7 days (this is safe)
• A follow-up appointment with your GP within 48-72 hours
• An appointment at the asthma clinic within 4 weeks

Preventing Future Attacks

• Take your preventer inhaler every day (usually brown, orange, or purple) — even when you feel well
• Check your inhaler technique — ask your pharmacist or nurse to watch you
• Have an Asthma Action Plan — a written plan for what to do when symptoms worsen
• Get your flu jab every year
• Avoid your known triggers where possible
• Don't smoke

Primary Guidelines

1. British Thoracic Society / SIGN. British Guideline on the Management of Asthma. 2019. PMID: 31594857
2. Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention. 2024. ginasthma.org
3. NICE. Asthma: diagnosis, monitoring and chronic asthma management (NG80). 2021. nice.org.uk/guidance/ng80

Key Studies

4. Goodacre S et al. Intravenous or nebulised magnesium sulphate versus standard therapy for severe acute asthma (3Mg trial): a double-blind, randomised controlled trial. Lancet Respir Med. 2014;2(4):293-300. PMID: 24717627
5. O'Driscoll BR et al. BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax. 2017;72(Suppl 1):ii1-ii90. PMID: 28507176
6. Kew KM et al. Intravenous magnesium sulfate for treating adults with acute asthma in the emergency department. Cochrane Database Syst Rev. 2014;(5):CD010909. PMID: 24865567

Further Reading

• Asthma UK: asthma.org.uk
• UpToDate: Acute exacerbations of asthma in adults
• Life in the Fast Lane: Asthma