Page 28 - ANZCP Gazette May 2023

1094696PRF0010.1177/02676591221094696PerfusionJabur et al.
research-artic le2022
Reprinted with kind permission from the journal – PERFUSION
Original Paper
A prospective observational study on the effect of emboli exposure on cerebral autoregulation in cardiac surgery requiring cardiopulmonary bypass
Ghazwan NS Jabur,1,2 Alan F Merry,2,3 Alastair McGeorge,4 Alana Cavadino,5 Joseph Donnelly2 and Simon J Mitchell2,3
Abstract
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.
Keywords
cardiopulmonary bypass; arterial gas embolism; brain function; decompression sickness; cerebral protection Date received: 7 January 2022; accepted: 30 March 2022
Introduction
Patients undergoing cardiac surgery may suffer brain injury manifesting as stroke or cognitive deficits.1 Stroke is the most feared of these complications and is more frequent after cardiac than non-cardiac operations in patients with similar risk factors.2 One commonly cited cause is cerebral hypoperfusion, which occurs when blood flow and oxygen delivery are insufficient to meet metabolic demands. Hypoperfusion is most likely in watershed regions that lie at the boundaries between vascular territories.3 These regions are particularly vul- nerable when perfusion pressures fall, a common event during cardiopulmonary bypass (CPB). A physiological
1Department of Clinical Perfusion, Auckland City Hospital, New Zealand
2Department of Anaesthesiology, Faculty of Medical and Health Sciences, University of Auckland, New Zealand
3Department of Anaesthesia, Auckland City Hospital, New Zealand 4Cardiovascular Intensive Care Unit, Auckland City Hospital, New
Zealand
5Epidemiology & Biostatistics, Faculty of Medical and Health Sciences,
University of Auckland, New Zealand
Corresponding author:
Ghazwan NS Jabur, Department of Clinical Perfusion, Auckland City Hospital, Level 4, 2 Park Road, Grafton, AUK 1023, New Zealand. Email: G.Jabur@auckland.ac.nz
25 MAY 2023 | www.anzcp.org
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