Oxygenated multidose delivery of crystalloid esmolol cardioplegia as an alternative to high potassium cardioplegia

Abstract

C ardioplegia is used as a myoprotective agent for the alleviation of surgically induced ischemic injury, incurred during cardiac operative procedures, to allow the functional preservation of the myocardium. These solutions allow for the rapid electromechanical arrest of the myocardium through alteration of cellular electrochemical gradients. 1 Most cardioplegic solutions use a high potassium content to arrest the heart. 2 The use of hypothermic potassium cardioplegia in adult cardiac surgery increases the safely available intraoperative time and has been correlated with improved postischemic myocardial functional recovery and reduced postoperative mortality. 3 Potassium-induced arrest maintains the heart in a depolarized state, significantly decreasing the energy demand of the myocardium, but basal metabolic energy requirements are sustained and thus still constitute a significant energy expenditure. 4 The advantages of cardioplegic arrest in providing a bloodless field are tempered by the fact that depolarization also leads to the alteration of ion flux across the sarcolemmal membrane and is associated with both increased cytosolic calcium accumulation and the significant depletion of cellular high-energy (adenosine triphosphate) reserves. [5][6][7][8][9] The use of blood cardioplegia is currently the criterion standard with which all cardioplegic formulations must be compared, and its benefits relative to crystalloid cardioplegia have been extensively reported. [10][11][12][13] Similarly, the relative contributions of hypothermia (cold, warm, and tepid cardioplegia) and the route of administration of cardioplegia (retrograde, antegrade, and combined retrograde and antegrade delivery) have been examined. [14][15][16][17][18] The applicability of high-potassium cardioplegia to the neonatal and immature heart remains poorly defined and will not be addressed here, but the reader is directed to reviews by del Nido 19 and Hammon 20 and the recent reviews of Allen and colleagues 21 and Ihnken 22 for further information.Despite continuous improvements in surgical technique and cardioplegic formulations, the inadequacies of current intraoperative myocardial protection protocols and formulations, most of which maintain as their basis high-potassium depolarizing arrest, remain a concern. Novel myoprotective protocols to allow enhanced functional recovery of the myocardium after ischemia and reperfusion continue to be needed. In this issue of the Journal, Bessho and Chambers 23 present evidence in favor of the use of oxygenated multidose crystalloid esmolol cardioplegia to induce cardiac arrest as an alternative to St Thomas' Hospital cardioplegic solution No. 2.Esmolol is an ultra-short acting (9-minute half-life) cardioselective ␤-blocker that is rapidly hydrolyzed by an esterase in the blood cell cytosol to an inactive form, thus avoiding the negative inotropic and chronotropic effects of prolonged ␤-block-

Potassium Concentration in Cardioplegic Solutions in Pediatric Patients Undergoing Tetralogy of Fallot Repair: Impact on Myocardial Protection

“…These findings of better myocardial protective effects in MP group when compared with conventional HP cardioplegia in pediatric patients were in agreement with our findings regarding the use of a cardioplegic solution with lower potassium concentration. Previous studies [6,8] have demonstrated that high-potassium cardioplegia can induce myocardial ionic and metabolic imbalances during ischemia, as well as myocardial stunning, tissue edema, endothelial damage, free radical production, and functional loss during reperfusion. More recently; non-depolarizing agents such as procaine, lidocaine, and esmolol, and hyperpolarizing agents such as adenosine and KATP channel openers (e.g., pinacidil, nicorandil, aprikalim, and cromakalim), have been suggested as a possible alternative to high potassium.…”

“…However, high potassium concentration has been associated with deleterious consequences against myocardial protection. A significant number of studies have shown a link between exposure to high potassium and post-cardioplegia ionic and metabolic imbalances, myocardial stunning, arrhythmia, ischemic injury, tissue edema, endothelial damage, free radical production, and functional loss during reperfusion [7,8]. Our hypothesis was testing whether the lower concentration of potassium in large volume cardioplegia could be used with similar or even better outcomes regarding myocardial protection.…”