Cardioplegia solutions and delivery methods, and myocardial protection strategies during cardiac surgery.
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- What is the main goal of cardioplegia during cardiac surgery?
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To rapidly arrest the heart in diastole and minimize myocardial oxygen demand, protecting the heart during ischemia- What ion is elevated in cardioplegia solution to arrest the heart electromechanically?
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Potassium- What is the mechanism by which high extracellular potassium arrests the heart?
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It depolarizes the resting membrane potential, inactivating fast sodium channels and preventing normal action potential propagation- What are the two main base fluid categories used for cardioplegia solution?
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Crystalloid cardioplegia and blood cardioplegia- What is the main theoretical advantage of blood cardioplegia over crystalloid cardioplegia?
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Blood carries oxygen and natural buffering and oncotic properties, providing some ongoing myocardial oxygen delivery during arrest- What is the typical ratio of blood to crystalloid in standard blood cardioplegia?
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Commonly around 4 parts blood to 1 part crystalloid, though ratios vary by protocol- What are the two main routes for cardioplegia delivery?
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Antegrade (via the aortic root or directly into coronary ostia) and retrograde (via the coronary sinus)- What is a key limitation of antegrade cardioplegia delivery in the presence of severe coronary artery disease?
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Distribution may be inadequate distal to critical stenoses or occlusions- What is a key advantage of retrograde cardioplegia delivery via the coronary sinus?
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It can provide protection to myocardium supplied by severely diseased or occluded coronary arteries independent of native flow- What is a common combined delivery strategy used to maximize myocardial protection?
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Combining antegrade and retrograde cardioplegia delivery in the same case- What is the purpose of intermittent cardioplegia redosing during a long cross-clamp period?
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To maintain adequate arrest, replenish protective substrate, and wash out accumulated metabolic byproducts- What temperature approach is used in cold cardioplegia?
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The solution is delivered cold, often around 4 to 10 degrees Celsius, to further reduce myocardial metabolic rate- What is warm (normothermic) blood cardioplegia intended to achieve differently than cold cardioplegia?
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Continuous aerobic metabolic support of the arrested heart at near-normal temperature rather than relying primarily on hypothermic metabolic suppression- What is a 'hot shot' in cardioplegia terminology?
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A terminal warm blood cardioplegia dose given just before releasing the aortic cross-clamp to aid metabolic recovery before reperfusion- What buffering agent is commonly added to cardioplegia solution to counteract ischemic acidosis?
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Bicarbonate or another buffer such as tromethamine (THAM)
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