Level 1 of 6Core
Acute severe asthma: grading and emergency treatment
The core to-do list — diagnose and manage, at a glance
Diagnose— recognise it
- Assess from across the room: speech (sentences → phrases → single words → mute), posture (unable to recline = severe), work of breathing (accessory muscles, retraction, paradoxical thoraco-abdominal movement), and mental state — agitation is usually hypoxaemia, drowsiness or confusion is pre-terminal.
- Acute severe asthma is defined by numbers, not impressions: PEF 33–50% of predicted or personal best (below 200 L/min), respiratory rate ≥ 25/min, heart rate ≥ 110/min, or inability to complete a sentence in one breath.
- Any one life-threatening feature redefines the attack: PEF < 33% or unable to blow, SpO₂ < 92%, PaO₂ < 8 kPa (60 mmHg), a normal or raised PaCO₂, silent chest, cyanosis, respiratory rate > 30/min or falling, pulse > 120/min or bradycardia, hypotension, exhaustion, delirium or drowsiness. Apply the oximeter before anything else — SpO₂ < 92% is the single strongest trigger for a blood gas.
- The single conceptual point: a patient in acute severe asthma should be blowing off carbon dioxide — a normal PaCO₂ (4.6–6.0 kPa, 35–45 mmHg) means the respiratory muscles are tiring, and a raised PaCO₂ above 6 kPa (45 mmHg) means they are failing. Never grade severity by the loudness of the wheeze — a silent chest means no air is moving.Not available at your setup — Arterial blood gas.
- Exhaustion, not recovery: a falling respiratory rate, a settled drowsy patient, bradycardia, hypotension or a new arrhythmia — and in children grunting, inability to feed, and a child who was working hard ten minutes ago and now appears calm.
- Paediatric severe thresholds: SpO₂ < 92%, too breathless to talk or feed, heart rate > 140/min (1–5 years) or > 125/min (over 5), respiratory rate > 40/min (1–5 years) or > 30/min (over 5); PEF is unreliable below about 5–6 years and must never delay treatment. Exclude anaphylaxis, pneumothorax, inhaled foreign body, bronchiolitis and croup before committing.
Manage now— do this, in order
- Sit the patient upright and keep them upright — never nurse an asthmatic flat; after 20 weeks of pregnancy use left lateral tilt if she must be reclined.
- Correct hypoxaemia immediately and completely: oxygen to SaO₂ 94–98% — sickest patients start on a reservoir (non-rebreathing) mask at 15 L/min or 40–60% by face mask, then titrate down. Never reduce the oxygen because the carbon dioxide is high — the 88–92% target belongs to COPD, not asthma.
- Salbutamol 5 mg nebulised, driven by oxygen at 6–8 L/min, repeated every 15–20 minutes — at least three treatments in the first hour. Never drive the nebuliser with an air compressor in a hypoxaemic patient. Child: 2.5 mg under 5 years, 5 mg from 5 years, every 20–30 minutes in the first hour.
- Add nebulised ipratropium bromide 500 microgram in the same chamber, repeated 4–6 hourly — routinely in life-threatening attacks and in anyone failing to respond to salbutamol; it reduces hospital admission rates. Child: 250 microgram under 12 years, 500 microgram from 12 years.
- Systemic corticosteroid to every patient in the first minutes: prednisolone 40–50 mg orally once daily for at least 5 days (no taper needed for ≤ 3 weeks) — it takes 4–6 hours to act, which is precisely why it cannot wait for the nebuliser response, and it must never be delayed while IV access is obtained. Child: soluble prednisolone 1–2 mg/kg once daily, maximum 40 mg, for 3–5 days.
- Reassess formally after the first dose and again after three doses (60–90 minutes): PEF, respiratory rate, SpO₂, pulse, speech and conscious level, each with a clock time; repeat the PEF 15–30 minutes after starting therapy and every 4–6 hours thereafter.
- Not responding — escalate: repeat salbutamol 5 mg with ipratropium 500 microgram or move to continuous salbutamol nebulisation at 5–10 mg/hour (monitor heart rate and potassium), and give magnesium sulphate 1.2–2 g IV over 20 minutes as a single dose with cardiac monitoring (child 40 mg/kg, max 2 g); slow the infusion if blood pressure falls.Doctor / Nurse
- Fluids and chemistry: 0.9% sodium chloride 500–1000 mL over the first one to two hours in an adult (child 10 mL/kg boluses, reassessed), and check and replace potassium and check glucose — repeated beta₂-agonists plus corticosteroids cause hypokalaemia, which is arrhythmogenic in a hypoxaemic patient. Sedatives, anxiolytics and hypnotics are contraindicated.Not available at your setup — Serum electrolytes.
- Assisted ventilation for coma, respiratory arrest, exhaustion, delirium or drowsiness, or deteriorating gases despite optimal therapy (PaO₂ < 8 kPa and falling, PaCO₂ > 6 kPa and rising, pH low and falling) — intubation is technically difficult and best performed semi-electively, before the crisis of respiratory arrest, after correcting volume status.Doctor / NurseNot available at your setup — Endotracheal intubation kit, Mechanical ventilator.
Grade the attack
| Grade | Defining features |
|---|---|
| Acute severe | PEF 33–50% of best, RR ≥ 25/min, HR ≥ 110/min, can't complete a sentence |
| Life-threatening | PEF < 33%, SpO₂ < 92%, PaO₂ < 8 kPa, normal/raised PaCO₂, silent chest, cyanosis, bradycardia, hypotension, exhaustion, drowsiness |
| Near-fatal | Raised PaCO₂ and/or mechanical ventilation with raised inflation pressures |
Refer / escalate
Call for critical care help immediately for any life-threatening or near-fatal feature — silent chest, SpO₂ below 92%, PEF below 33%, a normal or raised PaCO₂, cyanosis, feeble effort, bradycardia, hypotension, exhaustion, drowsiness or coma — or for failure to improve after three bronchodilator treatments in the first hour, and intubate semi-electively rather than waiting for respiratory arrest.
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