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Background/Objectives: Previously, we showed that blood-based polarizing cardioplegia exerted beneficial cardioprotection during hypothermic ischemia; however, these positive effects of blood-based polarizing cardioplegia were reduced during normothermic ischemia compared to blood-based hyperkalemic (depolarizing) cardioplegia. This study compares crystalloid polarizing cardioplegia to crystalloid depolarizing cardioplegia in a normothermic porcine model of cardiopulmonary bypass; Methods: Twelve pigs were randomized to receive either normothermic polarizing (n = 7) or depolarizing (n = 5) crystalloid cardioplegia. After the initiation of cardiopulmonary bypass, normothermic arrest (34 °C, 60 min) was followed by 60 min of on-pump and 90 min of off-pump reperfusion. Myocardial injury (arterial CK-MB), hemodynamic function, and the energy status of the hearts were measured; Results: The arterial release of CK-MB was comparable between groups (p = 0.78) during reperfusion. During 150 min of reperfusion, systolic left ventricular pressure (p = 0.01) and coronary flow (p = 0.009) were increased, and wedge pressure (p = 0.04) was decreased in the polarized group. Further hemodynamic parameters (cardiac output, stroke volume) and high-energy phosphate levels were similar between groups. The requirement for noradrenaline administration during reperfusion was significantly higher (p = 0.013) in the polarized group; Conclusions: Under normothermic conditions and despite a similar increase in levels of cardiac CK-MB, crystalloid polarizing cardioplegia protected systolic and diastolic cardiac function after 60 min of cardiac arrest. These results suggest beneficial effects for polarizing cardioplegia; clinical studies are required to confirm these effects. Full article

Despite current advances in perioperative care, intraoperative myocardial protection during cardiac surgery has not kept the same pace. High potassium cardioplegic solutions were introduced in the 1950s, and in the early 1960s they were soon recognized as harmful. Since that time, surgeons have minimized many of the adverse effects by lowering the temperature of the heart, lowering K⁺ concentration, reducing contact K⁺ time, changing the vehicle from a crystalloid solution to whole-blood, adding many pharmacological protectants and modifying reperfusion conditions. Despite these attempts, high potassium remains a suboptimalway to arrest the heart. We briefly review the historical advances and failures of finding alternatives to high potassium, the drawbacks of a prolonged depolarized membrane, altered Ca²⁺ intracellular circuits and heterogeneity in atrial-ventricular K⁺ repolarization during reanimation. Many of these untoward effects may be alleviated by a polarized membrane, and we will discuss the basic science and clinical experience from a number of institutions trialling different alternatives, and our institution with a non-depolarizing adenosine, lidocaine and magnesium (ALM) cardioplegia. The future of polarized arrest is an exciting one and may play an important role in treating the next generation of patients who are older, and sicker with multiple comorbidities and require more complex operations with prolonged cross-clamping times. Full article