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

Abstract

Pulse oximetry and measurement of regional cerebral oxygen saturation (rcSO₂) are used to monitor peripheral and cerebral oxygenation, respectively. However, the response of rcSO₂ and pulse oxygen saturation (SpO₂) 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 rcSO₂, SpO₂, 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 SpO₂ decreased to 90% or rcSO₂ decreased by >10% of the baseline level. The duration from pausing of mechanical ventilation to the start of the rcSO₂ decline was shorter than that of SpO₂ (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 rcSO₂ was longer than that of SpO₂ (84.8±24.3 sec vs. 15.2±6.8 sec; P<0.001). From the point where mechanical ventilation was paused to when rcSO₂/SpO₂ began to decrease, the rcSO₂ and SpO₂ 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 rcSO₂ or SpO₂ began to increase, rcSO₂ and SpO₂ 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 SpO₂, the rcSO₂ declined at a decreased rate (9.7±0.5% vs. 5.3±2.7%; P<0.001). The present clinical trial was registered at http://www.chictr.org.cn on 14th March 2016 (registration no. ChiCTR-OOC-16008095).

Keywords: children; hypoxia; pulse oxygen saturation; regional cerebral oxygen saturation.