Establishment of safer cerebral protection remains an important issue in reducing cerebral complications during aortic arch repair. Various cerebral perfusion techniques have been used. Recently, the usefulness of retrograde cerebral perfusion (RCP) combined with hypothermia was reported. The authors evaluated the cerebral microcirculation during RCP by direct observation with a charge-coupled device (CCD) microscope. In six craniotomied, anesthetized swine, cardiopulmonary bypass was established by arterial perfusion through the femoral artery and venous drainage from the right atrium. The authors observed cerebral arteriolae and venulae on the brain surface. Each swine was cooled to a brain temperature of 20°C. Perfusion was stopped, RCP was initiated with oxygenated blood through the superior vena cava, and cerebral perfusion pressure (CPP) was gradually increased. During antegrade cerebral perfusion (ACP), homogeneous vascular flow was observed in all models. During RCP, retrograde vascular flow was generated in four of the six models, but homogeneous retrograde vascular flow was achieved in arteriolae and venulae in only two models at a CPP of greater than 20 mmHg. It is suggested that homogeneous and effective retrograde perfusion may not be achieve at a CPP of less than 20 mmHg, and that RCP causes uneven microcirculation of the brain with a disadvantageous effect on cerebral protection when compared with ACP.
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