Efficacy of regional saturation of oxygen monitor using near-infrared spectroscopy for lower limb ischemia during minimally invasive cardiac surgery.

Lower limb ischemia with an occlusive cannula is a potential complication of minimally invasive cardiac surgery (MICS). We evaluated intraoperative local oxygen supply-demand balance by monitoring regional saturation of oxygen (rSO2) using near-infrared spectroscopy (NIRS), and analyzed the correlation between cannula size and fluctuation range of rSO2. Fifty-four patients undergoing MICS surgery using femoral artery cannulation from April 2015 to August 2016 were enrolled. The rSO2 of both the cannulated and uncannulated lower limbs were measured using NIRS. The association between the decline of rSO2 from baseline (delta-rSO2) and the ratio of the cannula diameter to the femoral artery diameter (Cd/FAd) was analyzed. Of the 54 patients, 16 (30%) (Group 1) showed values over 0.65 for Cd/FAd, and the remaining 38 (70%) (Group 2) showed values under 0.65. No patient developed postoperative lower limb ischemia. No patient was treated with an ipsilateral distal perfusion cannula. There were significant differences between Group 1 and Group 2 in the decrease of rSO2 at the point of cannulation on the cannulated limb. In the lower limb on the cannulated side, delta-rSO2 showed a significant decrease in Group 1 compared to Group 2 (Group 1 vs Group 2: 19.9 vs 11.0%; p < 0.001). Delta-rSO2 was significantly correlated with body surface aera (BSA), but not with gender or age. Decreasing rSO2 correlates with the Cd/FAd index. Low BSA, Cd/Fad > 0.65 is considered as the risk factor for decline of rSO2 in cannulated limb in MICS.