Critical Care - Theses
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ItemCITRIC-CPB: a prospective observational study evaluating the effects of cardiopulmonary bypass on plasma levels of vitamin C, electroencephalographic slow-wave activity, cerebral oxygenation & postoperative confusion in patients having cardiac surgery( 2023)Objective: Delirium is a common complication following cardiac surgery, attributed largely to heightened cerebral hypoxia and neuroinflammation from the use of cardiopulmonary bypass (CPB). Vitamin C (ascorbate) has both anti-inflammatory properties which may modulate neuroinflammation and has been observed to decrease after CPB. We aimed to determine the associations between delirium, electroencephalogram (EEG) activity, cerebral oxygenation, and plasma concentrations of ascorbate after cardiac surgery. Methods: A prospective observational design was adopted, with delirium diagnosed using the Confusion Assessment Method for ICU (CAM-ICU-7) or 3-minute Diagnostic Confusion Assessment Method (3D-CAM). Blood samples were collected immediately before surgery, after CPB and on post-operative days 1 – 4 for analysis of plasma ascorbate concentrations using UV-visible spectroscopy. Changes in frontal lobe slow-wave activity were assessed using EEG power in the 0.5 – 6Hz frequency range, and changes in cerebral oxygenation were assessed using cerebral near-infrared spectroscopy. Statistical comparison between patients with and without delirium were completed using a Mann-Whitney U test or unpaired t-test. Results: 20 patients undergoing cardiac surgery with CPB were recruited (25% female), with an average age of 63.05 (± 8.3) and average EuroSCORE of 2.16 (± 3.2). There were no differences in median ascorbate levels between delirium positive (10.644 μmol/L (9.692)) and delirium negative patients (8.507 μmol/L (4.217), p = 0.456) at any timepoints relative to baseline (pre-surgery). Additionally, no differences in median frontal EEG power were found between delirium positive (9.293 μV^2 (7.667)) and delirium negative patients (7.272 μV^2 (7.359), p = 0.250) relative to baseline. Lastly, no differences in mean cerebral oxygenation were found between delirium positive (53.36% (± 4.07)) and delirium negative patients (57.3% (± 4.35), p = 0.0525). 11 (55%) patients developed delirium after surgery. Conclusion: We detected no meaningful association between delirium development, ascorbate concentration, frontal EEG power or cerebral oxygenation in patients after cardiac surgery, suggesting other factors may contribute more significantly.