Protecting the brain from gaseous and solid micro-emboli during coronary artery bypass grafting: a randomized controlled trial

The purpose of the study was to investigate whether intra-operative filter devices protect the brain during coronary artery bypass grafting (CABG) and to determine the impact of solid and gaseous micro-emboli on neuropsychological functioning. Patients undergoing CABG received either an intra-aortic filter (Embol-X) (n = 43), designed to reduce solid micro-emboli, a dynamic bubble trap (DBT) (n = 50), designed to reduce gaseous micro-emboli, or no additional device (control group) (n = 50). Cognitive functioning was assessed before and 3 months after CABG. Micro-emboli signals (MES) were detected during surgery using transcranial Doppler (TCD) sonography. Cerebral magnetic resonance imaging (MRI) was carried out before and after surgery. Primary endpoint was the cognitive outcome of the filter groups compared with the controls. Analysis of covariance was performed using the post-operative cognitive test scores as continuous variables in covariance of the corresponding pre-operative scores. Secondary endpoints were the MES rates and the number of acute ischaemic lesions after CABG. Compared with the controls, cognitive functioning of the DBT group was better in executive functioning (t = 2.525, P = 0.0065) and verbal short-term memory (t = 2.420, P = 0.009). The Embol-X group did not perform better in any test. The total number of MES was lower in the DBT group (median 99, P = 0.0019), but not in the Embol-X group (median 162.5, P > 0.05), both compared with controls (median 164.5). After surgery, 17 patients displayed small ischaemic brain lesions on MRI with equal distribution between the groups. Gaseous micro-embolization contributes to neuropsychological decline, which is measurable 3 months post-operatively. No filter device could protect the brain during CABG completely. However, the use of the DBT tends to improve the cognitive outcome after CABG. Gas filters are recommendable for neuroprotection during cardiac surgery.