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Cardioplegia markedly reduces oxygen demand in the arrested heart and must be delivered uniformly in sufficient quantity to match this low demand.
“Integrated myocardial protection” is a myocardial protection strategy that includes antegrade and retrograde delivery of cold-blood cardioplegia and warm cardioplegia perfusion for induction and resuscitation.
Hypothermia reduces myocardial oxygen demand and ischemic injury when coronary flow is interrupted; however, it does not completely prevent injury in chronically ischemic hearts.
Blood cardioplegia, which typically comprises four parts blood to one part crystalloid solution, is a natural buffering agent, maintains oncotic pressure, possesses advantageous rheologic properties, and is a free-radical scavenger.
High potassium in cardioplegia maintains cardiac arrest and prevents sudden intracellular calcium accumulation and sarcolemma disruption.
Complete myocardial recovery occurs after 4 h of ischemia in normal hearts when protected with cold-blood cardioplegia.
Antegrade or retrograde delivery of cardioplegia alone does not provide homogeneous distribution even with normal coronary arteries.
Paradoxical septal motion, seen in up to 40 percent of cardiac surgical patients, can lead to acute right ventricular failure and may be caused by inadequate distribution of cardioplegia.
Warm-blood cardioplegia induction limits reperfusion injury in ischemic hearts.
During antegrade infusion of cardioplegia, aortic pressure should be maintained between 60 and 80 mm Hg at a flow rate of 200 cm3/min or, in hypertrophied hearts, at 250 cm3/min.
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A successful outcome after cardiac surgery depends on many factors. Accurate recognition of the pathology and the judicial choice of methods to achieve cardiac repair are essential. Equally important are the physiologic consequences of the operation. Ventricular function must be preserved or improved during cardiac procedures. Myocardial protection is therefore the crucial component of success in cardiac surgery.
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The mainstay of myocardial protection is cardioplegia. This chapter is a brief review of myocardial protection as currently applied in the vast majority of cardiac operations worldwide. We offer a brief review of the components of cardioplegia and their effects on cardiac metabolism and function, followed by a detailed description of “how to do it.”
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Much has been written about cardioplegia regarding (1) route of delivery (antegrade vs retrograde or both), (2) method of delivery (continuous vs intermittent), and (3) temperature (warm vs cold). This has often led to confusion and adversarial positions. Surgeons appropriately want to keep things simple, but as Einstein once said: “Everything should be made as simple as possible, but not simpler.” In this chapter, we present a method of cardioplegia that has been extensively applied clinically. It is called the “integrated method” of protection because it combines the salient features of the above elements in a manner that suits the ongoing physiologic needs of the heart during the course of an operation and expedites the time phase of the procedure.
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Basis of Cardioplegia
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Cardioplegia markedly reduces oxygen demand in the arrested ...