Brain natriuretic peptide (BNP) may play a major role in risk stratification based on cerebral oxygen saturation by near-infrared spectroscopy in patients undergoing major cardiovascular surgery

PURPOSE: A previous study reported that low baseline cerebral oxygen saturation (ScO(2)) (≤50%) measured with near-infrared spectroscopy was predictive of poor clinical outcomes after cardiac surgery. However, such findings have not been reconfirmed by others. We conducted the current study to evaluate whether the previous findings would be reproducible, and to explore mechanisms underlying the ScO(2)-based outcome prediction. METHODS: We retrospectively investigated 573 consecutive patients, aged 20 to 91 (mean ± standard deviation, 67.1 ± 12.8) years, who underwent major cardiovascular surgery. Preanesthetic baseline ScO(2), lowest intraoperative ScO(2), various clinical variables, and hospital mortality were examined. RESULTS: Bivariate regression analyses revealed that baseline ScO(2) correlated significantly with plasma brain natriuretic peptide concentration (BNP), hemoglobin concentration (Hgb), estimated glomerular filtration rate (eGFR), and left ventricular ejection fraction (LVEF) (p < 0.0001 for each). Baseline ScO(2) correlated with BNP in an exponential manner, and BNP was the most significant factor influencing ScO(2). Logistic regression analyses revealed that baseline and lowest intraoperative ScO(2) values, but not relative ScO(2) decrements, were significantly associated with hospital mortality (p < 0.05), independent of the EuroSCORE (p < 0.01). Receiver operating curve analysis of ScO(2) values and hospital mortality revealed an area under the curve (AUC) of 0.715 (p < 0.01) and a cutoff value of ≤50.5% for the baseline and ScO(2), and an AUC of 0.718 (p < 0.05) and a cutoff value of ≤35% for the lowest intraoperative ScO(2). Low baseline ScO(2) (≤50%) was associated with increases in intubation time, intensive care unit stay, hospital stay, and hospital mortality. CONCLUSION: Baseline ScO(2) was reflective of severity of systemic comorbidities and was predictive of clinical outcomes after major cardiovascular surgery. ScO(2) correlated most significantly with BNP in an exponential manner, suggesting that BNP plays a major role in the ScO(2)-based outcome prediction.