Abstract
Nearinfrared spectroscopy (NIR) is a procedure which permits noninvasive measurement of cerebral oxygenated and deoxygenated hemoglobin. The purpose of this study is to examine how accurately NIR represents separate and nonoverlapping dimensions among monitoring modalities during cardiopulmonary bypass (CPB). In 66 patients (50 male, 16 female, age 30-74 (mean 63.8 ±9.9) yrs) who underwent coronary artery bypass grafting during CPB, 321 sampling points were defined. Arterial blood pressure, central venous pressure, pulmonary arterial pressure, perfusion index, arterial hemoglobin concentration, and esophageal temperature were recorded at every sampling point. Oxygen and carbondioxide partial pressure and oxygen saturation were measured in arterial and venous blood. Cerebral oxygenated, deoxygenated, and total hemoglobin were measured by NIR spectroscopy. We used the multivariate statistical technique of factor analysis. Seven factors are extracted and rotated orthogonally through the Varimax procedure. Bartlett's chi-square test of the correlation matrix is significant at the 0.0001 level. We have named the factors Oxygen, Cerebral Oxygen, Carbondioxide, Left-Heart, Right-Heart, Perfusion Index, and Hemoglobin. Cerebral Oxygen factor contains NIR-measured cerebral oxygenated and deoxygenated hemoglobin. We conclude that NIR spectroscopy monitored separate and distinct clinical dimensions during CPB. NIR may be a useful new monitoring tool for assessing cerebral oxygenation in open-heart surgery.
