Acute asthma
Grade the attack with peak flow and SpO₂, give back-to-back nebulisers and steroids, add magnesium if it is not working, and fear the patient who goes quiet.
A 24-year-old woman with asthma is wheezy and breathless after three days of a cold. It is smog season. She can only say a few words at a time. RR 30, pulse 122, SpO₂ 93%, peak flow 160 L/min (her best is 420).
How bad is this attack, and what do you do now?
- Sit her up, oxygen if neededKeep SpO₂ 94–98%.
- Salbutamol nebuliser nowDriven by oxygen. Back-to-back if severe.
- Grade the severityPeak flow (as % of best or predicted), ability to speak, RR, pulse, SpO₂.
- Add ipratropiumFor acute severe or life-threatening attacks, or poor response.
- Steroids for everyonePrednisolone by mouth, or IV hydrocortisone if she cannot swallow.
- ABG if SpO₂ is below 92%Or any life-threatening sign. A normal CO₂ is a danger sign.
- Reassess after each nebuliserPeak flow, SpO₂, speech, RR, pulse.
- Call your senior earlyIf severe or not improving after the first nebulisers.
- Peak flow below 33% of best or predicted
- SpO₂ below 92%
- Silent chest, cyanosis or poor breathing effort
- Exhausted, confused or drowsy
- Low BP or arrhythmia
- Normal or high CO₂ on the gas
- Not improving after 2–3 nebulisers
- Life-threatening and near-fatal asthma
- Pneumothorax
- Anaphylaxis presenting as wheeze
- Pneumonia triggering the attack
- A COPD or heart failure patient labelled as asthma
| Severity | Peak flow 33–50% of best = acute severe. Below 33% = life-threatening |
| Salbutamol | 5 mg nebulised every 15–30 minutes, or continuously if severe |
| Steroids | Prednisolone 40–50 mg by mouth, or hydrocortisone 100 mg IV every 6 hours |
| Not improving | Senior review for IV magnesium (doses in the treatment section) |
| Potassium | Salbutamol lowers it. Check and replace |
Check every dose against a current drug reference and your hospital protocol.
On this page
Why asthma still kills
Most asthma attacks settle quickly with nebulisers and steroids. People still die of asthma in hospital, and it is usually for the same reasons: the severity was underestimated, steroids were late, or the patient was sedated. The most dangerous patient is the one who looks calm because she is exhausted and has stopped moving air.
In Pakistan, attacks cluster in the smog season in Punjab, around crop burning, and in people who stopped their preventer inhaler because they "felt fine".
Grading the attack
Measure the peak flow if the patient can do it (do not force someone with life-threatening features), and compare with her best or the predicted value for her age, sex and height.
- Peak flow 50–75%
- Speaking in sentences
- No severe features
- Any of: peak flow 33–50%
- RR 25 or more
- Pulse 110 or more
- Cannot finish sentences in one breath
- Any of: peak flow below 33%
- SpO₂ below 92%
- Silent chest, cyanosis, poor effort
- Exhaustion, confusion, arrhythmia, low BP
- PaO₂ below 60 mmHg (8 kPa) or a "normal" PaCO₂
A raised PaCO₂ (above 45 mmHg, 6 kPa), or the need for ventilation. In an attack, a breathless patient should be blowing off CO₂, so the CO₂ should be low. A normal or rising CO₂ means she is tiring. Call ICU now.
History
- How long, how bad, and what set it off (cold, smoke, smog, dust, exercise, aspirin or NSAIDs, beta-blockers).
- Usual inhalers: does she have a preventer (an inhaled steroid) and does she use it? How often does she need her reliever?
- Previous ICU admission or ventilation: this patient is at high risk of dying. Tell your senior.
- Courses of oral steroids in the past year, and recent admissions.
- Smoking and smoke exposure at home (cooking fires, huqqa).
- Pregnancy: treat an attack exactly the same way. The baby is at more risk from the attack than from the drugs.
Examination
- Can she speak in full sentences? RR, pulse, SpO₂, BP.
- Wheeze and air entry. A silent chest is not improvement: it means very little air is moving.
- One side quieter than the other: think pneumothorax.
- Rash, lip or tongue swelling, low BP: think anaphylaxis.
- Conscious level: drowsiness is a late and serious sign.
Wheeze that is not asthma
| Condition | Points towards it | Test that helps |
|---|---|---|
| COPD flare | Older smoker or biomass exposure, chronic sputum | History, ABG, spirometry later |
| Anaphylaxis | Trigger, rash, swelling, low BP | Clinical. Give IM adrenaline |
| Pneumothorax | Sudden pain, one-sided signs | Chest X-ray |
| Pulmonary oedema ("cardiac asthma") | Older, heart disease, crackles, raised JVP | Chest X-ray, ECG |
| Inhaled foreign body | Sudden onset after choking, one-sided wheeze | Chest X-ray, bronchoscopy |
| Pneumonia | Fever, focal crackles | Chest X-ray |
Investigations
| Test | When and why |
|---|---|
| Peak flow | Before and 15–30 minutes after each treatment |
| SpO₂ | Everyone. Below 92% needs an arterial gas |
| ABG | SpO₂ below 92% or any life-threatening feature. Look at the CO₂ |
| Chest X-ray | Not routine. Do it if pneumothorax or pneumonia is possible, the attack is life-threatening, or there is no response |
| Potassium | Salbutamol and steroids lower it |
| Blood sugar | Steroids raise it, especially in diabetics |
Treatment
- OxygenTo keep SpO₂ 94–98%.
- Salbutamol5 mg by oxygen-driven nebuliser. Repeat every 15–30 minutes, or back-to-back in severe attacks.
- Ipratropium500 micrograms nebulised, mixed with the salbutamol, for acute severe or life-threatening attacks.
- SteroidsPrednisolone 40–50 mg by mouth now. IV hydrocortisone if she cannot swallow.
- ReassessPeak flow, SpO₂ and the patient after each nebuliser.
- Not improvingSenior review. IV magnesium sulfate, a single dose.
- Still not improvingICU review. Aminophylline only on senior or ICU advice.
No sedatives for an anxious, breathless asthmatic: no diazepam, no promethazine, not even "a small dose to calm her down". Sedation stops a tiring patient from breathing.
- Life-threatening features not improving with treatment.
- Rising PaCO₂ or falling pH.
- Exhaustion, drowsiness, confusion.
- Poor breathing effort or respiratory arrest.
Going home or staying in
- Can usually go home
- Steroids for 5 days
- Preventer inhaler and technique check
- Clinic in 1–2 weeks
- Admit
- Senior review
- Continue nebulisers and steroids
Admit if: previous near-fatal attack, pregnant, presenting at night, poor support at home, or already on oral steroids
- Prednisolone 40–50 mg daily to complete at least 5 days.
- A preventer inhaler (inhaled steroid). Explain it works over weeks, not minutes, and must be used every day.
- Check inhaler technique, with a spacer. Many attacks are poor technique.
- A written plan: when to increase treatment and when to come back.
- Avoid smoke, and advise staying indoors on high-smog days where possible.
- Medical clinic review within 1–2 weeks.
Common mistakes
- Underestimating severity because she looks calm. Check the peak flow, SpO₂ and CO₂.
- Calling a silent chest an improvement.
- Forgetting the steroids, or giving them late.
- Sedating an anxious asthmatic.
- Sending her home on a reliever only, without a preventer.
- Forgetting the potassium after repeated salbutamol.
Frequently asked questions
What are the signs of life-threatening asthma?
Peak flow below 33% of best or predicted, SpO₂ below 92%, silent chest, cyanosis, poor breathing effort, exhaustion, confusion, arrhythmia, low BP, or a normal or high PaCO₂.
What is the dose of magnesium sulfate in acute asthma?
A single dose of 1.2–2 g IV over 20 minutes in adults with acute severe or life-threatening asthma not responding to nebulisers. It is a senior decision.
How often can salbutamol nebulisers be given?
Every 15–30 minutes in a severe attack, or continuously in life-threatening asthma, with monitoring of pulse and potassium.
Do all asthma attacks need steroids?
Yes. Every adult treated in hospital for an asthma attack should get steroids: prednisolone 40–50 mg daily for at least 5 days.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A 25-year-old woman with asthma has peak flow 40% of her best, RR 27, pulse 115 and SpO₂ 95%. She can only speak in short phrases. How severe is this attack?
Answer: Acute severe asthma. Acute severe asthma: any of peak flow 33–50% of best, RR 25 or more, pulse 110 or more, or unable to complete sentences. Treat with oxygen, back-to-back salbutamol, ipratropium and steroids, and get a senior review.
- Mild, suitable for discharge: Far from mild.
- Moderate exacerbation: Peak flow 33–50% with these features is severe.
- Life-threatening asthma: Life-threatening needs peak flow below 33%, SpO₂ below 92%, silent chest, exhaustion or similar.
- Near-fatal asthma: Near-fatal means a raised PaCO₂ or need for ventilation.
2. A 19-year-old with acute asthma has had three salbutamol nebulisers. The wheeze has become quiet but she is now drowsy. What does this mean?
Answer: Life-threatening asthma: call ICU and check an ABG. A silent chest, drowsiness, exhaustion or confusion are life-threatening features. Get senior and ICU help immediately; she may need intubation.
- Start oral prednisolone and recheck in 4 hours: She needs urgent escalation now.
- Anxiety resolving; discharge later: Dangerous misreading of a peri-arrest sign.
- Salbutamol side effect; observe: Drowsiness is a sign of exhaustion and rising CO₂.
- She is improving; reduce nebulisers: A silent chest with drowsiness means very little air movement.
3. A breathless asthmatic in the emergency department has PaCO₂ 46 mmHg (6.1 kPa). How should this be interpreted?
Answer: Near-fatal asthma. In acute asthma, hyperventilation lowers CO₂. A normal or raised PaCO₂ means respiratory muscle fatigue: near-fatal asthma.
- Lab error; repeat tomorrow: Act on it now.
- Normal, so reassuring: In an attack the CO₂ should be low from fast breathing.
- Chronic CO₂ retention: That pattern belongs to COPD, not acute asthma in a young adult.
- Expected after salbutamol: Salbutamol does not raise CO₂.
4. A 30-year-old with asthma has PEF 30% of best, SpO₂ 91%, silent chest and is drowsy. PaCO₂ is 6.2 kPa. What does this indicate?
Answer: Life-threatening asthma. Life-threatening features: PEF < 33%, SpO₂ < 92%, silent chest, cyanosis, poor effort, arrhythmia, exhaustion, altered consciousness, hypotension, and a 'normal' PaCO₂ (4.6–6.0) or rising CO₂ (near-fatal). Treat with oxygen, nebulised salbutamol and ipratropium, oral/IV steroids, IV magnesium sulfate 2 g, and ICU referral for intubation.
- Moderate exacerbation: There are too many severe features for a moderate exacerbation.
- Improving asthma: A normal or raised CO₂ is ominous, not a sign of improvement.
- Anxiety-related hyperventilation: Hyperventilation does not cause a silent chest.
5. A 6-year-old with acute asthma can’t complete sentences, RR 40, SpO₂ 91%, HR 140. What is the first treatment?
Answer: Oxygen + salbutamol. Acute severe asthma in children: can’t complete sentences, SpO₂ < 92%, tachycardia, tachypnoea. Give high-flow oxygen, salbutamol (10 puffs via spacer or nebulised 2.5–5 mg) repeated, ipratropium if poor response, oral prednisolone (1–2 mg/kg) or IV hydrocortisone; IV magnesium or salbutamol/aminophylline for life-threatening features (silent chest, exhaustion, confusion) with PICU input.
- Oral montelukast: Montelukast is not for acute severe asthma.
- Chest physiotherapy: Physiotherapy does not help acute asthma.
- IV aminophylline first: Aminophylline is not first-line.
6. Which analgesic should be avoided after surgery in a patient with asthma that worsens with aspirin?
Answer: Diclofenac. In aspirin-exacerbated respiratory disease, blocking COX shifts arachidonic acid towards leukotrienes, causing bronchospasm. All non-selective NSAIDs (diclofenac, ibuprofen, ketorolac) can trigger it. Paracetamol, local anaesthetics and carefully monitored opioids are used instead.
- Paracetamol: Safe at normal doses.
- Morphine with monitoring: Can be used with care.
- Local anaesthetic wound infiltration: Safe and opioid-sparing.
- Patient-controlled intravenous fentanyl: Can be used with monitoring.
7. A patient on theophylline develops vomiting, tachycardia and seizures after starting ciprofloxacin. Why?
Answer: Ciprofloxacin inhibits CYP1A2. Theophylline (phosphodiesterase inhibitor and adenosine antagonist) has a narrow therapeutic range (10–20 mg/L). Inhibitors of CYP1A2 (ciprofloxacin, erythromycin, cimetidine) raise levels, causing nausea, arrhythmias and seizures. Smoking and enzyme inducers lower levels. Hypokalaemia is common in toxicity.
- Ciprofloxacin induces its metabolism: It inhibits, not induces.
- Direct ciprofloxacin cardiotoxicity: Not the mechanism.
- Allergic reaction: Not the mechanism.
- Theophylline withdrawal: Not the mechanism.
References and dose sources
- BTS/SIGN British guideline on the management of asthma
- Global Initiative for Asthma (GINA) report
- NICE NG245 — asthma (BTS, NICE, SIGN)
- Salbutamol dosing: Drugs.com: Albuterol (salbutamol) dosage (see also our salbutamol dose page)
- Ipratropium bromide dosing: Drugs.com: Ipratropium dosage (see also our ipratropium bromide dose page)
- Prednisolone dosing: Drugs.com: Prednisolone dosage (see also our prednisolone dose page)
- Hydrocortisone dosing: Drugs.com: Hydrocortisone dosage (see also our hydrocortisone dose page)
- Magnesium sulfate dosing: Drugs.com: Magnesium sulfate dosage (see also our magnesium sulfate dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.