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Acute chest syndrome in sickle cell disease — MRCEM SBA MCQ

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HardRespiratory emergenciesAcute chest syndrome in sickle cell diseaseMRCEM SBA

A 29-year-old woman with HbSC sickle cell disease attends the emergency department with limb pain, fever and new pleuritic chest pain. Chest radiography shows new bilateral lower-zone infiltrates. She has received analgesia and intravenous antibiotics covering typical and atypical respiratory pathogens. Over the next two hours, her oxygen requirement rises from 2 L/min by nasal cannulae to 40% Venturi oxygen to maintain SpO₂ at 94%. Her respiratory rate is 32/min. She is alert, speaking normally and haemodynamically stable; arterial pH is 7.40 and PaCO₂ is 4.6 kPa. Haemoglobin is 101 g/L, compared with her usual 106 g/L. What is the most appropriate escalation and disposition plan?

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Correct answer: C — Arrange urgent red-cell exchange and admit her to a high-dependency unit.

New pulmonary infiltrates with fever, chest pain and worsening hypoxaemia in a patient with sickle cell disease indicate acute chest syndrome. Her rapidly increasing oxygen requirement and bilateral involvement are concerning features of progression, despite antibiotics. Her haemoglobin is already 101 g/L: a simple transfusion offers little scope to raise it without increasing blood viscosity. UK specialty guidance recommends exchange transfusion for severe acute chest syndrome or when haemoglobin is above 90 g/L. Urgent haematology and critical-care involvement, red-cell exchange and high-dependency monitoring are therefore the best plan; oxygen, antibiotics and analgesia continue. ([stgeorges.nhs.uk](https://www.stgeorges.nhs.uk/wp-content/uploads/2020/02/BSH-guidelines-Acute-Chest-Syndrome-SCD-2016.pdf)) A is attractive because early simple transfusion can help hypoxic patients, but her relatively high haemoglobin favours exchange. B selects the appropriate transfusion but underestimates the monitoring needed for rapidly worsening oxygenation. D may become an adjunct if respiratory support is required, but does not replace indicated exchange transfusion. E would take priority if she could not protect her airway or developed worsening respiratory failure despite less invasive support; she currently has neither feature. ([stgeorges.nhs.uk](https://www.stgeorges.nhs.uk/wp-content/uploads/2020/02/BSH-guidelines-Acute-Chest-Syndrome-SCD-2016.pdf))

Reference: British Society for Haematology: Guideline on the management of acute chest syndrome in sickle cell disease (May 2015) — https://www.stgeorges.nhs.uk/wp-content/uploads/2020/02/BSH-guidelines-Acute-Chest-Syndrome-SCD-2016.pdf British Society for Haematology: Guidelines on red cell transfusion in sickle cell disease Part II: indications for transfusion (January 2017) — https://www.stgeorges.nhs.uk/wp-content/uploads/2020/02/BSH-Red-Cell-Transfusion-SCD-part-2-indications-for-transfusion-2016.pdf St George’s University Hospitals NHS Foundation Trust: Acute complications of sickle cell disease, section 6.2 (2020) — https://www.stgeorges.nhs.uk/wp-content/uploads/2020/02/SGH_HN506a_guidelines-Acute-complications-of-SCD.pdf