The mechanism of Blood-brain barrier disturbance after cardiopulmonary bypass in cardiovascular surgery

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Marked cerebral swelling visible on magnetic resonance images has been found immediately after cardiopulmonary bypass (CPB) and may be the cause of neuropsychological disorders after cardiovascular surgery. In autopsy patients, microembolization due to cardiopulmonary bypass can be detected in the brain as lipid deposits that create small capillary and arteriolar dilations (SCADs). This lipid emboli possibly come from cardiotomy suction blood and become the cause of cerebral swelling. But this interaction has not been explored. The purposes of this study are to examine the effect of returning the cardiotomy suction blood to the blood-brain barrier in rabbit model and whether serum concentrations of S100b protein and neuron specific enolase (NSE) are predictors of cerebral damage in clinical cases of cardiovascular surgery.Animal study. Sternotomy of the rabbit was done and infusion line was cannulated into the ascending aorta via left ventricle (after heparinization). The mediastinal c … More avity was manipulated for 90 min and 75 ml suction blood was returned into the cannula under transcranial Doppler monitor on right eye (n=6). Only cannulation was done in the control rabbits (n=6). The blood-brain barrier impairment (of the right side the brain) was evaluated with the measurement of extravasated evans blue. The left side brain was dried at 110℃ for 24hr and water content was calculated. The rest of the right side of the brain was used as histopathologic evaluation. During returning the cardiotomy suction blood, multiple emboli was detected on TCD monitor and the extravasation of evans blue occur significantly in this animal. The water content was not larger than control group. There was significant difference not in MAP2 staining but in GFAP staining (increase) between groups.Human study. S100b and NSE were measured in the blood obtained at 7 time points during and after operation in eighteen patients with conventional CPB and seven with selective cerebral perfusion (SCP). Concentrations of these markers were also examined in the blood of surgical field and cell saving device. The mean values of S100b in CPB group (2.08 ± 2.00 ng ml^<-1>) and SCP group (1.46 ± 0.77 ng ml^<-1>) were largest after aortic declamp and after termination of SCP, respectively. The mean values of NSE in CPB group (29.1±14.0 ng ml^<-1>) and SCP group (31.2 ±13.6 ng ml^<-1>) were largest after termination of CPB and at the end of operation, respectively. Three patients suffered from cerebral complications but the elevation of these markers during operation was indistinguishable from those in the other patients. S100b protein and NSE concentrations in the blood of surgical field were significantly larger than those in arterial blood, while these concentrations of the blood in cell saving device were not elevated.The maneuver of returning the cardiotomy suction blood into ascending aorta become the cause of contamination of S100b protein and NSE and impairment of blood-brain barrier. Less