Noninvasive tissue oxygen saturation determined by near-infrared spectroscopy following peripheral nerve block

Background Noninvasive physiologic measurement of cutaneous tissue oxygenation using near‐infrared spectroscopy (NIRS) has become increasingly common in cardiovascular and plastic surgery. The aim of this study was to determine whether clinically available NIRS‐based monitors could detect changes in tissue oxygen saturation (rSO2) following a variety of peripheral nerve blocks. We hypothesize that peripheral nerve blocks will produce detectable changes in cutaneous tissue oxygenation levels that can be measured by noninvasive NIRS‐based oximetry. Methods Forty adult patients scheduled for pre‐operative peripheral nerve block placement were enrolled. Prior to block placement, NIRS sensors were placed on the operative and nonoperative (control) limb. Baseline tissue oxygen saturation values were obtained prior to dosing of the nerve block, and measurements were recorded every 5 min thereafter. Results Initial rSO2 values were higher in the operative vs. control limbs prior to nerve block placement. Tissue oxygen saturation increased in the blocked, but not control, limbs with time. Subgroup analysis suggested statistically significant differences in rSO2 values in blocked vs. control limbs for cervical paravertebral, infraclavicular, and femoral nerve blocks. Conclusions Our results demonstrated sustained increases in tissue rSO2 values following peripheral nerve block placement, in addition to higher initial rSO2 values in operative limbs prior to block placement. Further investigations are necessary to define the expected baseline rSO2 values in operative and control limbs. Future efforts utilizing NIRS‐based detection of tissue ischemia should consider the small but significant changes in rSO2 resulting from a successful nerve block.