SctO2

SctO2, or regional cerebral tissue oxygen saturation, is a value obtained with near-infrared spectroscopy (NIRS) monitoring that estimates the oxygen saturation of the cerebral tissue in the frontal cortex. It reflects the balance between cerebral oxygen delivery and consumption, representing a weighted mix of arterial and venous blood, with venous blood contributing the majority.

Measurement is performed using NIRS devices that emit near-infrared light through the scalp and skull and detect how the light is absorbed by oxyhemoglobin and deoxyhemoglobin. From these measurements, the device computes a tissue saturation value that typically ranges from about 0 to 100 percent. Readings can be influenced by scalp blood flow, skull thickness, hematocrit, skin pigmentation, carbon dioxide levels, temperature, and the effects of anesthetic or vasoactive drugs. Baseline values and target ranges are device- and patient-specific.

In clinical practice, SctO2 monitoring is used during anesthesia and in critical care to detect cerebral hypoxia early and guide management aimed at optimizing cerebral oxygen delivery. It is considered an adjunct to other monitoring modalities, such as arterial oxygen saturation and invasive measures of perfusion, rather than a standalone measure of global brain oxygenation. Clinicians commonly look for maintenance of SctO2 near baseline and for avoidance of significant desaturation, though specific thresholds vary by device and protocol.

Limitations include its regional nature—it monitors a superficial portion of the cortex and may be influenced by extracranial tissues. Readings can lag behind true cerebral events, and there is no universal threshold applicable to all patients or devices. Therefore, SctO2 interpretation relies on trend analysis, device-specific norms, and integration with other clinical data.