Associations between baseline cerebral oxygen saturation, preoperative B-type natriuretic peptide and hemoglobin levels, and mortality after cardiac surgery in non-dialysis patients.

Baseline cerebral regional oxygen saturation (rSO₂) measured with the INVOS 5100C near-infrared spectroscopy (NIRS) device has been reported to correlate primarily with preoperative B-type natriuretic peptide (BNP) and hemoglobin levels. It has also been reported to be associated with postoperative mortality. This study evaluated whether similar associations exist for other NIRS-derived indicators, including tissue oxygenation index (TOI) and tissue oxygen saturation (StO₂), measured with the NIRO-200NX and FORESIGHT Elite devices, respectively. We retrospectively analyzed 510, 468, and 510 non-dialysis adult patients undergoing cardiac surgery in whom baseline rSO₂, TOI, and StO₂, respectively, were measured on the forehead before anesthesia and mixed venous oxygen saturation (SmvO₂) was measured after induction of anesthesia. Correlations between 37 preoperative blood test variables and NIRS or SmvO₂ values were evaluated using Spearman's correlation coefficient. Associations between baseline NIRS values and postoperative in-hospital mortality were assessed using logistic regression. Across all three devices, baseline NIRS values and SmvO₂ values were most significantly correlated with BNP and hemoglobin (all p < 0.00001) of the 37 preoperative blood test variables. Baseline rSO₂, TOI, and StO₂ values were each significantly associated with postoperative mortality (p = 0.00101, 0.00111, and 0.01122, respectively). For all NIRS-derived indicators examined, baseline NIRS values before anesthesia and SmvO₂ values after induction of anesthesia were primarily correlated with BNP and hemoglobin levels. In addition, baseline NIRS values showed a significant association with postoperative in-hospital mortality, suggesting their potential utility as a prognostic marker, although this requires confirmation in larger studies.