Acute Asthma

Question 1

How common is it?

Answer 1

• Affects 5-8% of the population.

Question 2

Who does it affect?

Answer 2

• Children (boys more than girls), adults and old people with exposure to risk factors can develop it (gender difference disappears in adults).

Question 3

What causes it?

Answer 3

• Characterized by recurrent episodes of dyspnoea, cough and wheeze caused by reversible airways obstruction. Three factors contribute to this obstruction:
  1. Bronchial muscle contraction, triggered by a variety of stimuli.
  2. Mucosal swelling/inflammation, caused by mast cell and basophil degranulation resulting in release of inflammatory mediators.
  3. Increased mucus production.

Question 4

What risk factors are there (and how can they be reduced)?

Answer 4

Family history, having another atopic condition (allergy, eczema, hay fever), being overweight, smoking (inc passive smoking), exposure to pollution or occupational triggers.

Question 5

How does it present?

Answer 5

Symptoms - Intermittent dyspnoea, wheeze, cough (often nocturnal) and sputum. Should ask specifically about:

• Precipitants – cold air, exercise, emotion, allergens, infection, smoking, pollution, NSAIDs, beta-blockers.
• Diurnal variation in symptoms or peak flow. Marked morning dipping of peak flow is common.
• Exercise – quantify exercise tolerance.
• Disturbed sleep.
• Acid reflux – in 40/60%.
• Other atopic disease – eczema, hay fever, allergy or family history.
• Job – do symptoms remit at weekends or holidays?

Signs – Tachypnoea, audible wheeze, hyperinflated chest, hyperresonant percussion note, reduced air entry, widespread polyphonic wheeze. In acute attack: inability to complete sentences, pulse >110bpm, respiratory rate >25/min, PEF 30-50% expected.

Question 6

Which other conditions may present similarly?

Answer 6

Pulmonary oedema (‘cardiac asthma’), COPD (may co-exist), large airway obstruction (eg foreign body, tumour), SVC obstruction (wheeze, dyspnoea not episodic), pneumothorax, PE, bronchiectasis, obliterative bronchiolitis (suspect in elderly).

Question 7

How would you investigate the patient?

Answer 7

Acute attack – PEF, sputum culture, FBC, U&E, CRP, blood cultures. ABG analysis usually shows a normal or slightly reduced PaO2 but reduced PaCO2 (hyperventilation).

Chronic asthma – PEF monitoring: a diurnal variation of >20% on >3d a wk for 2wks. Spirometry: obstructive defect (↓FEV1/FVC, ↑RV); usually >15% improvement in FEV1 following B2 agonists or steroid trial. CXR: hyperinflation.

Question 8

What treatment/s would you consider? What risks and benefits of treatment are there?

Answer 8

Acute:
Immediate treatment:
- Salbutamol 5mg (or terbutaline 10mg) nebulized with O2.
- Hydrocortisone 100mg IV or prednisolone 40-50mg PO or both if very ill.
- Start O2 if sats <92%, aim for 94-98%.

If life threatening features present:

• Inform ICU and seniors.
• Give salbutamol nebulizers every 15min, or 10 mg continuously per hour. Monitor ECG; watch for arrhythmias.
• Add inipratropium 0.5mg to nebulizers.
• Give single dose of magnesium sulphate 1.2-2g IV over 20 mins.

If improving within 15-30 minutes:

• Nebulized salbutamol every 4 hours.
• Prednisolone 40-50mg PO OD for 5-7 days.
• Monitor peak flow and O2 sats, aim 94-98% with supplemental if needed.