A Prospective Observational Study on the Effect of Emboli Exposure on Cerebral Autoregulation in Cardiac Surgery Requiring Cardiopulmonary Bypass.

Jabur GN, Merry AF, McGeorge A, Cavadino A, Donnelly J, Mitchell SJ.

Perfusion. 2022 May 21. Online ahead of print

Objective

Cerebrovascular autoregulation impairment has been associated with stroke risk in cardiac surgery. We hypothesized that greater arterial emboli exposure in open-chamber surgery might promote dysautoreguation.

Methods

Forty patients underwent closed or open-chamber surgery. Transcranial Doppler detected emboli and measured bilateral middle cerebral artery flow velocities. Cerebral autoregulation was assessed by averaging the mean velocity index (“Mx,” a continuous moving correlation between cerebral blood flow velocity and mean arterial pressure) over 30 min before and after aortic cross-clamp removal.

Results

Median (interquartile range) emboli counts were 775 (415, 1211) and 2664 (793, 3734) in the closed-chamber and open-chamber groups. Most appeared after the removal of the aortic cross-clamp (open-chamber 1631 (606, 2296)), (closed-chamber 229 (142, 384)), with emphasis on the right hemisphere (open-chamber: 826 (371, 1622)), (closed-chamber 181 (66, 276)). Linear mixed model analyses of mean velocity index change showed no significant overall effect of group (0.08, 95% CI: −0.04, 0.21; p = 0.19) or side (0.01, 95% CI: −0.03, 0.05; p = 0.74). There was an interaction between group and side (p = 0.001), manifesting as a greater increase in mean velocity index in the right hemisphere in the open than the closed group (mean difference: 0.15, 95% CI: 0.02, 0.27; p = 0.03).

Conclusions

Overall, change in mean velocity index before and after cross-clamp removal did not differ between groups. However, most emboli entered the right cerebral hemisphere where this change was significantly greater in the open-chamber group, suggesting a possible association between embolic exposure and dysautoregulation.