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Effect of cardiopulmonary bypass on cortical cerebral oxygenation during coronary artery bypass grafting
Sudath P Talpahewa1, A Timothy Lovell, Gianni D Angelini
1Cardiothoracic Surgery, Bristol Heart Institute, Bristol Royal Infirmary, University of Bristol, Bristol BS2 8HW, UK.
Insights
Coronary artery bypass grafting (CABG) surgery temporarily reduces oxygenated hemoglobin and cerebral blood volume. While oxygen levels recover, blood volume deficits persist, indicating potential autoregulation issues during cardiopulmonary bypass (CPB).
Area of Science:
- Cardiovascular Surgery
- Neuroanesthesia
- Cerebral Physiology
Background:
- Coronary artery bypass grafting (CABG) involves cardiopulmonary bypass (CPB), potentially impacting cerebral oxygenation.
- Monitoring brain function during CPB is crucial for patient outcomes.
Purpose of the Study:
- To assess changes in cerebral oxygenation during normothermic CABG using near-infrared spectroscopy (NIRS).
- To evaluate the impact of CPB on oxygenated hemoglobin ([O(2)Hb]), cerebral blood volume (CBV), and other neuromonitoring parameters.
Main Methods:
- NIRS was used to measure [O(2)Hb], deoxygenated hemoglobin ([HHb]), cytochrome c oxidase ([Cyt-Ox]), tissue oxygenation index (TOI), and tissue hemoglobin index (THI) in 19 patients.
- Data were collected at various time points during normothermic CPB (34-36°C).
Main Results:
- A significant reduction in [O(2)Hb] and CBV was observed during CPB, worsening at 40 minutes (P<0.0001).
- [O(2)Hb] levels recovered by surgery's end, but CBV reduction persisted.
- No significant changes were noted in [HHb], [Cyt-Ox], or TOI.
Conclusions:
- Normothermic CABG with CPB causes reversible [O(2)Hb] decrease and persistent CBV reduction.
- These findings suggest transient impairment of cerebral blood flow autoregulation after CPB discontinuation.
Objective:
To investigate the changes in cerebral oxygenation during coronary artery bypass grafting (CABG) with normothermic cardiopulmonary bypass (CPB) using near infrared spectroscopy.
Methods:
Measurement of cerebral cortical oxygenation changes included concentration of deoxygenated haemoglobin [HHb], oxygenated haemoglobin [O(2)Hb], changes in the redox status of the cytochrome c oxidase [Cyt-Ox], cerebral saturation as expressed by the tissue oxygenation index (TOI), and cerebral blood volume (CBV) as expressed by tissue haemoglobin index (THI). Measurements were performed in 19 consecutive patients undergoing normothermic (34-36 degrees C) CPB. Data were recorded at 0.5s intervals and averaged into 30 s epochs. Data analysis was carried at baseline, 1, 20, and 40 min after start of CPB, at rewarming, on weaning from CPB, and at closing of chest.
Results:
There were no in-hospital death, neurological deficits, or myocardial infarcts. Compared to baseline, during the entire CPB duration, there was a marked reduction in [O(2)Hb] and CBV which reached their worst level 40 min after initiation of CPB (from -3.03+/-5.1 to -9.25+/-7.20 micromol/l for [O(2)Hb], and a 24% reduction for CBV (both P<0.0001). The deterioration in [O(2)Hb] was recovered by the end of surgery, while the changes in CBV persisted. No significant changes occurred with respect to [HHb], [Cyt-Ox], and TOI.
Conclusions:
Conventional CABG is responsible for deterioration in [O(2)Hb], and CBV, which peak at 40-60 min following initiation of CPB. The changes in [O(2)Hb] are reversible whereas the reduction of CBV persists to the end of the surgery. This suggests a transient impairment in the autoregulatory mechanisms controlling cerebral blood flow following discontinuation of cardiopulmonary bypass.
