Do surface-modifying additive circuits reduce the rate of cerebral microemboli during cardiopulmonary bypass?

The objective of this study was to determine if surface-modifying additive (SMA) cardiopulmonary bypass (CPB) circuits are associated with a lower rate of cerebral microemboli during CPB compared with standard circuits. In a 2 x 2 factorial design, patients undergoing coronary artery bypass graft surgery were randomized to SMA or standard CPB circuits (with and without methyl-prednisolone). Transcranial Doppler was used to detect high-intensity transient signals (HITS) in both middle cerebral arteries. HITS were counted from onset to end of CPB. Intervals of interest were as follows: period 1, from CPB onset to aortic cross-clamping; period 2, from aortic cross-clamping to immediately before de-clamping; period 3, from aortic declamping to before aortic side-clamping; period 4, from the application of the aortic side clamp to immediately before the release of the side clamp; period 5, from aortic side clamp release to the end of CPB. There were 14 patients in each circuit group. No significant differences were found on the partial and total counts of HITS (medians [25th, 75th percentile]) between patients exposed to standard (total count: 228 HITS [174, 2801) and SMA circuits (total count: 156 HITS [104, 356]; p = .427). The median of the sum of HITS per patient associated with perfusionist interventions was not different between both circuit groups (standard: 17 HITS [7, 80]; SMA: 43 HITS [13, 168]; p = .085). This study, with a sample size of 28 patients, indicates that it is unlikely to find any difference in the count of HITS during CPB that is greater than 117 HITS between the two CPB circuits. Moreover, our findings emphasize the relevance of minimizing additional sources of cerebral microembolization during CPB that are not directly related to the biocompatible nature of the SMA CPB circuit.