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Acute Severe Asthma — RACP Adult Medicine MCQ

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ModerateRespiratoryAcute Severe AsthmaRACP Adult Medicine

A 35-year-old man presents to ED with acute severe asthma. He can speak in phrases. HR 120, RR 28, SpO₂ 92% on room air. PEF is 40% predicted. He has received 3 salbutamol nebulisers and ipratropium with moderate improvement (PEF now 55%). IV hydrocortisone has been given. What is the most appropriate next step?

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Correct answer: E — IV magnesium sulfate 2 g over 20 minutes

IV magnesium sulfate (2 g over 20 minutes) is recommended for acute severe asthma with incomplete response to initial bronchodilator therapy. It provides additional bronchodilation via smooth muscle relaxation. The 3MHAST trial and meta-analyses support its use as add-on therapy. It is particularly useful when patients plateau on inhaled bronchodilators.

Reference: Australian Asthma Handbook – 2024 – Acute Severe Asthma; eTG Respiratory 2024