Prediction of plasma hemoglobin concentration by near-infrared spectroscopy

The estimation of plasma hemoglobin concentration (Hb) is among one of the daily activities in the practice of clinical anesthesiology. The near-infrared spectroscopy of the brain (rSO(2)) represents a balance between cerebral oxygen delivery and consumption. This study was designed to assess the value of rSO(2) in the prediction of the Hb level while other variables were mathematically controlled. Thirty healthy adult patients undergoing spine surgery, expected to have a moderate degree of intraoperative bleeding, were enrolled in this study. General anesthesia was given and ventilation was mechanically controlled. Measurement of Hb and PaCO(2) were performed at random periods of time. We obtained a total of 97 data combinations for the 30 study patients. The Hb was regressed by independent variables including rSO(2) and PaCO(2). A multilinear regression analysis was performed and the final regression equation was expressed only with statistically significant variables. The measured Hb was tightly regressed with three variables. The final regression equation was Hb=+8.580+0.238.rSO(2)-0.338.PaCO(2)-0.004.anesthetic exposure duration (Tmin) (p=0.000, r(2)=0.809). Near-infrared spectroscopy was shown to be a valuable predictor of plasma Hb in the clinical anesthesiology setting.