Comparing the response of pulse oximetry and regional cerebral oxygen saturation to hypoxia in preschool children.

Pulse oximetry and measurement of regional cerebral oxygen saturation (rcSO(2)) are used to monitor peripheral and cerebral oxygenation, respectively. However, the response of rcSO(2) and pulse oxygen saturation (SpO(2)) to hypoxia in preschool children has not been previously assessed. A total of 36 preschool patients who had undergone a tonsillectomy [age, 4-6 years, American Society of Anesthesiologists grade I or II] were screened and prospectively enrolled in the present study. Hemodynamics, including rcSO(2), SpO(2), non-invasive blood pressure, heart rate, electrocardiogram and capnography, were continuously monitored throughout the study. Following pre-oxygenation, pressure-controlled ventilation with 100% oxygen was administered through a mask with a flow rate of 6 l/min, under total intravenous anesthesia, and the end-tidal carbon dioxide partial pressure was maintained between 30 and 40 mmHg. Tracheal intubation was then performed and ventilation was paused until SpO(2) decreased to 90% or rcSO(2) decreased by >10% of the baseline level. The duration from pausing of mechanical ventilation to the start of the rcSO(2) decline was shorter than that of SpO(2) (80.2 +/- 23.6 sec vs. 124.4 +/- 20.5 sec; P<0.001). Subsequent to the recovery of ventilation, the duration from the starting point to the increasing point of the baseline of rcSO(2) was longer than that of SpO(2) (84.8 +/- 24.3 sec vs. 15.2 +/- 6.8 sec; P<0.001). From the point where mechanical ventilation was paused to when rcSO(2)/SpO(2) began to decrease, the rcSO(2) and SpO(2) values decreased and a significant correlation of them was observed (Pearson's correlation coefficient=0.317; P=0.027). From the time-point where mechanical ventilation was recovered to the time-point where rcSO(2) or SpO(2) began to increase, rcSO(2) and SpO(2) values decreased and a significant correlation of them was observed (Spearman's correlation coefficient=0.489; P=0.006). From the baseline to the minimum value, compared with the SpO(2), the rcSO(2) declined at a decreased rate (9.7 +/- 0.5% vs. 5.3 +/- 2.7%; P<0.001).