Related Subjects:
|Sickle Cell Disease
|Acute Chest Syndrome (Sickle Cell)
|Exchange Transfusion
🔥 Acute chest syndrome (ACS) is one of the most serious acute complications of sickle cell disease (SCD) and a leading cause of death.
Think of it in any patient with SCD who develops chest pain, fever, cough, dyspnoea, or a fall in oxygen saturation, especially during or after a vaso-occlusive crisis.
🚨 Urgent haematology review is needed, and HDU/ICU escalation should be considered early if there is hypoxia, rapid progression, multilobar disease, or increasing work of breathing.
🩺 Definition
- Acute chest syndrome is usually defined as a new pulmonary infiltrate on chest imaging together with fever and/or new respiratory symptoms or signs in a person with SCD.
- Typical triggers and mimics overlap, so in practice ACS and pneumonia are often treated simultaneously.
- NICE advises assessing for ACS in any acute sickle crisis with chest pain, respiratory symptoms/signs, fever, or hypoxia.
📊 Epidemiology
- ACS is a major cause of morbidity and a leading cause of mortality in SCD.
- It is particularly common in HbSS and HbSβ⁰ thalassaemia.
- Lifetime risk is substantial, and recurrence after a first episode is common.
- Children have the highest incidence, but adults often have more severe disease and worse outcomes.
⚡ Pathophysiology / Triggers
- Infection: viral or bacterial infection can trigger inflammation, hypoventilation, and sickling within the pulmonary circulation.
- Fat embolism: bone marrow infarction during vaso-occlusive crisis can release marrow fat into the lungs.
- Pulmonary vaso-occlusion / infarction: sickled erythrocytes obstruct the pulmonary microcirculation, causing ischaemia and inflammation.
- Hypoventilation: chest wall pain, opioid-related oversedation, postoperative splinting, or atelectasis can precipitate or worsen ACS.
- Asthma / bronchospasm and aspiration may also contribute.
🔍 Clinical Features
- New or worsening chest pain, often during a vaso-occlusive pain crisis.
- Fever, cough, tachypnoea, dyspnoea, and increased work of breathing.
- Hypoxia or a fall in oxygen saturation from the patient’s baseline.
- Wheeze, crackles, or reduced air entry.
- Falling haemoglobin, rising inflammatory markers, and worsening pain may accompany deterioration.
🚨 Red Flags
- Rapidly increasing oxygen requirement.
- Respiratory distress, exhaustion, or altered consciousness.
- Multilobar infiltrates or progressive radiological change.
- Failure to improve despite oxygen, antibiotics, analgesia, and supportive care.
- Haemodynamic instability or concern about impending respiratory failure.
🧪 Investigations
- Urgent chest X-ray to look for a new infiltrate.
- FBC and reticulocyte count: anaemia, reticulocytosis, leucocytosis.
- U&Es, CRP, LFTs, bilirubin, and group-and-save / crossmatch.
- Blood cultures if febrile; consider sputum culture and respiratory viral testing where relevant.
- ABG or VBG if hypoxic or clinically unwell.
- ECG and consideration of alternative cardiopulmonary pathology if presentation is atypical.
- CT pulmonary angiography only if PE or another diagnosis is strongly suspected and results would change management.
🛠️ Immediate Management
- Admit to hospital and involve haematology early.
- Give oxygen if hypoxic, aiming to restore the patient to their normal saturation or to a safe target.
- Start prompt analgesia, but avoid oversedation and hypoventilation.
- Incentive spirometry should be encouraged regularly while awake, especially if ACS complicates a painful crisis.
- Start antibiotics early because pneumonia and ACS frequently coexist.
- Use IV fluids carefully: avoid dehydration, but also avoid fluid overload which can worsen respiratory status.
- Consider bronchodilators if wheeze or coexisting reactive airways disease is present.
💉 Transfusion
- Transfusion should be considered early, especially in hypoxic patients.
- Simple (“top-up”) transfusion may be appropriate in less severe or early disease, especially if the haemoglobin has fallen significantly below baseline.
- Exchange transfusion is indicated for severe ACS or if there is clinical deterioration, worsening hypoxia, progressive infiltrates, or poor response to simple transfusion.
- UK transfusion guidance commonly targets a post-exchange HbS <30% in severe acute syndromes such as severe ACS.
- Avoid over-transfusion because excessive haemoglobin rise can increase blood viscosity.
🧫 Antibiotics
- Give broad-spectrum antibiotics with atypical cover.
- A common practical regimen is a cephalosporin or co-amoxiclav plus a macrolide, adjusted for age, local policy, allergies, severity, and microbiology.
- If severe sepsis, hospital-acquired infection, or resistant organisms are concerns, escalate according to local guidance and microbiology advice.
💊 Supportive Care
- Careful opioid use with regular reassessment of respiratory rate and sedation level.
- Chest physiotherapy is not routinely emphasised as strongly as incentive spirometry, which has better supporting evidence in this setting.
- VTE prophylaxis should be considered in adults unless contraindicated.
- Escalate early to critical care if non-invasive or invasive respiratory support may be needed.
🛡️ Prevention
- Hydroxycarbamide (hydroxyurea) reduces recurrent painful crises and ACS in appropriate patients.
- Vaccination and infection prevention are important, including influenza and pneumococcal protection.
- Penicillin prophylaxis remains important in many children with SCD.
- During painful crises, good analgesia plus incentive spirometry can reduce the risk of developing ACS.
- Some patients with recurrent severe ACS may require a regular transfusion programme after specialist review.
🎓 Clinical Pearl
- SCD + new chest symptoms + fever and/or hypoxia = ACS until proven otherwise.
- Do not wait for profound radiographic change before escalating treatment.
- The common bedside trap is to think “just pneumonia” or “just pain splinting” — in practice, ACS often overlaps with these and should be treated urgently.
📚 Key UK References
- British Society for Haematology – Management of Acute Chest Syndrome in Sickle Cell Disease.
- British Society for Haematology – Guidelines on red cell transfusion in sickle cell disease.
- NICE CKS – Sickle cell disease.
- NICE QS58 – Acute complications in sickle cell disease.
