The majority of cardiac surgical procedures are accomplished using cardioplegia-induced cardiac arrest, with CPB to maintain perfusion to other organs. However, in certain situations the nature of the surgical procedure or the pathology of the underlying condition necessitates complete cessation of blood flow (Table 61.1). Preservation of organ function during the period of total circulatory arrest can be achieved by reducing the core temperature of the body. The technique of core cooling combined with cessation of blood flow is termed “deep hypothermic circulatory arrest” (DHCA). DHCA provides excellent operating conditions – albeit of limited duration – whilst ameliorating the major adverse consequences of organ ischemia. By reducing cellular metabolism, hypothermia preserves high-energy phosphate stores and protects organs from short periods of ischemia. The brain is the organ most vulnerable to injury, but may be protected if cooled to reduce oxygen-dependent neuronal metabolic activity and excitatory neurotransmitter release before and during the period of arrest. Similarly, other organs that are less susceptible to ischemic damage may be protected by core cooling.
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