The Changes of Tissue Oxygen Saturation Under Spinal Anesthesia

Neuraxial anesthesia affords a less interventional way to desensitization of the lower body for surgical procedures. After introduction of neuraxial anesthesia, vasodilatation of body part below the anesthetic level is theoretically appeared as the sympathetic nerve efferent is blocked. The vasodilatation effect is related to hypotension, hypothermia, shivering and the response of volume redistribution. It is believed that vasodilatation leads to better regional tissue perfusion and better regional tissue oxygenation. Previous reports of laser doppler flowmetry and thermography showed their effectiveness on monitoring blocked level but they were not easily available in the operation room. Recently Near-infrared spectroscopy(NIRS) demonstrates real-time tissue oxygen saturation(rSO2) which is applied generally in non-invasive brain oximeter. We use NIRS in spinal anesthesia to monitor the tissue oxygenation change over the upper and lower limbs during the induction of neuraxial anesthesia.