Increased cerebrovascular resistance after retrograde cerebral perfusion: a Doppler study

Deep hypothermic circulatory arrest (DHCA) with retrograde cerebral perfusion (RCP) under high central venous pressure (CVP) is often used in aortic arch surgery under cardiopulmonary bypass (CPB). We hypothesized that DHCA with RCP under high CVP causes cerebral vascular compression because of increased perivascular pressure due to extravasation of fluid into intracranial tissue. In a retrospective study, we evaluated the pulsatility index (PI) and resistance index (RI) of the internal carotid arteries (ICA) and external carotid arteries (ECA) before and after CPB in 15 patients who underwent DHCA/RCP (group 1) and 17 patients who underwent regular CPB without DHCA/RCP (group 2). Both indices are known to reflect vascular resistance distal to the measurement point. The PI and RI of the ICA increased significantly after the procedure in group 1 but did not change in group 2. The PI and RI of the ECA did not change in either group. In group 1, the rate of increase in PI and RI correlated with the duration of RCP, which was significantly higher in patients who had postoperative delirium than in patients who did not experience postoperative delirium. As increases in PI/RI after DHCA/RCP occurred only in the ICA, we concluded that the changes were due to compression of vessels as a result of increased perivascular pressure. The greater increase in the PI/RI in patients who experienced postoperative delirium indicates that increased perivascular pressure plays a role in the occurrence of postoperative delirium after DHCA/RCP.