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.