What are the American Heart Association (AHA) guidelines for managing patients with sickle cell anemia undergoing cardiac surgery?

Guidelines for Sickle Cell Anemia in Cardiac Surgery

Critical Note on AHA Guidelines

No specific American Heart Association (AHA) guidelines exist for managing sickle cell disease patients undergoing cardiac surgery. The most authoritative guidance comes from the 2021 Association of Anaesthetists guideline, which provides comprehensive recommendations for this high-risk population 1.

Pre-operative Transfusion Strategy

Exchange transfusion is the preferred transfusion modality before cardiac surgery when automated apheresis is available 1.

Transfusion Approach by Genotype:

• All genotypes undergoing high-risk surgery (including cardiac surgery): Exchange transfusion targeting hemoglobin of 100 g/L 1
• Goal HbS level: Reduce to <30% for safe cardiopulmonary bypass, with some centers achieving <15% 2
• Timing: Complete exchange transfusion before surgery or during bypass initiation 1, 3

Alternative Approaches (when exchange unavailable):

• Simple top-up transfusion during and after bypass has been used successfully in matched pair analyses showing no significant difference in outcomes compared to controls 1
• Partial exchange transfusion can reduce HbS from 84-90% to 9-34% pre-operatively 3

Intra-operative Management During Cardiopulmonary Bypass

Temperature Management:

• Cool to the minimum temperature necessary - avoid excessive hypothermia as it promotes sickling 1
• Maintain normothermia whenever possible; hypothermia causes shivering and peripheral stasis increasing sickling risk 1
• Even deep hypothermic circulatory arrest has been performed successfully with appropriate precautions 1

Oxygenation and Acid-Base:

• Careful monitoring and management of arterial and mixed venous oxygen levels is mandatory 1
• Maintain strict pH control - avoid acidosis which promotes sickling 1, 4
• Pre-oxygenation before induction is essential 1
• Use controlled ventilation to achieve good oxygenation and normocarbia if intubated 1

Bypass Technique:

• Standard bypass care using systemic hypothermia, aortic cross-clamping, and cold crystalloid antegrade cardioplegia can be used safely 1
• Consider using "discard" cardiotomy reservoir and priming oxygenator with donor blood to reduce circulating HbS/HbC levels intraoperatively 2
• Intraoperative plasmapheresis can sequester plasma and clotting factors from discarded blood 2

Post-operative Management

Oxygenation Protocol:

• Administer oxygen continuously to keep SpO2 above baseline or 96% (whichever is higher) for 24 hours or until the following morning if freely mobilizing 1
• Continue oxygen monitoring until saturation maintained at baseline in room air 1
• Oxygen therapy may be required at night for several nights, particularly after thoracic surgery 1

Respiratory Support:

• Early mobilization and physiotherapy are essential 1
• Incentive spirometry every 2 hours to prevent acute chest syndrome 1, 5
• Consider CPAP, high-flow nasal oxygen, or nasopharyngeal prong airway 1
• Bronchodilator therapy for patients with history of small airways obstruction or acute chest syndrome 1

Fluid Management:

• Meticulous fluid management with accurate measurement and replacement of losses 1
• Continue IV fluids until adequate oral intake tolerated 1
• Monitor fluid balance closely - patients have impaired urinary concentrating ability and dehydrate easily 1
• Consider central venous pressure and cardiac output monitoring 1

Pain Management:

• Continue baseline long-acting opioid medication throughout peri-operative period 1
• Implement multimodal analgesia (local/regional blocks, PCA, nurse-controlled analgesia, oral analgesia) 1
• Notify pain team in advance for major surgery 1
• Use validated pain assessment scales and reassess regularly 1
• Patients may have opioid sensitivity rather than dependency 1

Monitoring Requirements:

• Standard monitoring per anesthesia guidelines 1
• Consider near-infrared spectroscopy for cerebral oxygenation monitoring 1
• Neuromuscular monitoring mandatory if blocking drugs used - ensure full reversal before extubation 1

Level of Care:

• Consider high-dependency or ICU care post-operatively, especially for complex cardiac procedures 1, 5
• Hematology team should be immediately available for any sickle cell complications 1

Thromboprophylaxis:

• All post-pubertal patients require thromboprophylaxis due to increased DVT risk 5

Common Pitfalls to Avoid

• Excessive hypothermia during bypass - cool only to minimum necessary temperature 1
• Inadequate pre-operative transfusion - exchange transfusion is preferred, not simple top-up 1
• Hypoxia at any point - maintain vigilant oxygenation monitoring and supplementation 1, 4, 3
• Dehydration - these patients cannot concentrate urine and require aggressive hydration 1
• Inadequate pain control - leads to stress response that can precipitate crisis 1
• Premature discontinuation of oxygen - continue until SpO2 stable at baseline in room air 1