Page 18 - ANZCP Gazette NOVEMBER 2022

1023897
research-artic
Reprinted with kind permission from the journal – PERFUSION
le2021
Original Paper
A prospective observational study of emboli exposure in open versus closed chamber cardiac surgery
Ghazwan NS Jabur,1,2 Joseph Donnelly,2 Alan F Merry2,3 and Simon J Mitchell2,3
Abstract
Objective: Exposure to cerebral emboli is ubiquitous and may be harmful in cardiac surgery utilizing cardiopulmonary bypass. This was a prospective observational study aiming to compare emboli exposure in closed-chamber with open- chamber cardiac surgery, distinguish particulate from gaseous emboli and examine cerebral laterality in distribution. Methods: Forty patients underwent either closed-chamber procedures (n = 20) or open-chamber procedures (n = 20). Emboli (gaseous and solid) were detected using transcranial Doppler in both middle cerebral arteries in two monitoring phases: 1, initiation of bypass to the removal of the aortic cross-clamp; and 2, removal of aortic cross-clamp to 20 minutes after venous decannulation.
Results: Total (median (interquartile range)) emboli counts (both phases) were 898 (499–1366) and 2617 (1007–5847) in closed-chamber and open-chamber surgeries, respectively. The vast majority were gaseous; median 794 (closed- chamber surgery) and 2240 (open-chamber surgery). When normalized for duration, there was no difference between emboli exposures in closed-chamber and open-chamber surgery in phase 1: 6.8 (3.6–15.2) versus 6.4 (2.0–18.1) emboli per minute, respectively. In phase 2, closed-chamber surgery cases were exposed to markedly fewer emboli than open- chamber surgery cases: 9.6 (5.1–14.9) versus 43.3 (19.7–60.3) emboli per minute, respectively. More emboli (total) passed into the right cerebral circulation: 985 (397–2422) right versus 376 (198–769) left.
Conclusions: Patients undergoing open-chamber surgery are exposed to considerably higher numbers of cerebral arterial emboli after removal of the aortic cross-clamp than those undergoing closed-chamber surgery, and more emboli enter the right middle cerebral artery than the left. These results may help inform the evaluation of the pathophysiological impact of emboli exposure.
Keywords
cardiac; cerebral circulation; cerebral protection; embolism; perfusion; cardiopulmonary bypass (CPB); stroke
Introduction
The passage of small arterial bubbles into the cerebral arterial circulation is ubiquitous in cardiac surgery involving cardiopulmonary bypass (CPB). Whether this contributes to post-operative cognitive dysfunction (POCD) or stroke has been widely debated and recently reviewed.1,2 A synthesis of relevant evidence acknowl- edged approximate equipoise, and observed that the likely multifactorial causation of POCD following car- diac surgery could confound attempts to demonstrate correlations between outcome and a single risk factor;2 especially where a risk-factor-of-interest (like arterial bubble exposure) cannot be intentionally manipulated to provide wide separation between comparator groups in human studies.
One stratification of cardiac surgery patients that may allow comparison of exposure to consistently high versus (comparatively) lower numbers of arterial bub- bles is the separation into groups undergoing open- chamber surgery (OCS) (such as aortic or mitral valve
1Department of Clinical Perfusion, Auckland City Hospital, Auckland, New Zealand
2Department of Anesthesiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
3Department of Anesthesia, Auckland City Hospital, Auckland, New Zealand
Corresponding author:
Ghazwan NS Jabur, Department of Clinical Perfusion, Auckland City Hospital, Level 4, 2 Park Road Grafton, Auckland 1023, New Zealand. Email: G.Jabur@auckland.ac.nz
15 NOVEMBER 2022 | www.anzcp.org
Perfusion 1–7 © The Author(s) 2021 Article reuse guidelines: sagepub.com/journals-permissions httpDs:O//dIo: i1.o0r.g1/107.711/0727/607265769519211210102233897 journals.sagepub.com/home/prf