The Effect of Hypotension on Cerebral Metabolism and Perfusion in Adults Undergoing Cardiopulmonary Bypass: A Prospective Cohort Study
Bibliographic record
Abstract
BACKGROUND: Current blood pressure management strategies cannot accommodate large interindividual variations in cerebral autoregulation, which may result in inadvertent cerebral ischemia. A novel optical neuromonitoring device was developed to explore the relationships between blood pressure and cerebral metabolism and hemodynamics during hypotension on cardiopulmonary bypass and the transition on bypass in cardiac surgery. METHODS: Forty-five elective adult patients were monitored by a hybrid optical device incorporating broadband near-infrared spectroscopy for monitoring changes in tissue oxygen saturation and the oxidative state of cytochrome c oxidase (oxCCO) in the brain along with diffuse correlation spectroscopy for measuring a cerebral blood flow index. Changes in the optical variables were evaluated. RESULTS: Seventy-four hypotensive events were associated with significant decreases (mean ± standard deviation) in oxCCO (-0.55 ± 0.18 μM), cerebral blood flow index (-48% ± 20%), and tissue oxygen saturation (-9% ± 5%, P < .001) when mean arterial pressure fell below 50, 35, and 25 mm Hg, respectively. Decreases in oxCCO corresponding to literature-defined cerebral blood flow lesion and functional thresholds were -1.10 and -0.87 μM. During transition on bypass, mild reductions in blood pressure and body temperature (34.9 ± 0.6°C) occurred without significant cerebral blood flow changes. Multiple linear regression demonstrated reduction in oxCCO was significantly associated with temperature and blood pressure (R 2 = 0.92, P < .001), while tissue oxygen saturation and cerebral blood flow index had weaker associations (R 2 = 0.75, P < .001; R 2 = 0.42, P = .002, respectively). No significant changes in scalp oxCCO and tissue oxygen saturation were found during hypotensive episodes or CPB transition. CONCLUSIONS: This study identifies oxCCO as an optical variable that is highly responsive to hypotension. The work also highlights the link between blood pressure and cerebral metabolism and hemodynamics, offering potential insights into optimizing current blood pressure management.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".