Near-infrared spectroscopy underestimates cerebral oxygenation in hemodialysis patients.

Regional cerebral oxygen saturation (rSO2) measured using near-infrared spectroscopy has been reported to be significantly lower in hemodialysis (HD) patients than in non-HD ones, but the mechanisms are unknown. The aim of this prospective study was to assess the accuracy of near-infrared spectroscopy to estimate cerebral oxygenation in HD patients undergoing cardiovascular surgery. Our hypothesis was that rSO2 values would underestimate cerebral oxygenation in HD patients. This study included 113 patients (7 HD patients and 106 non-HD ones) undergoing cardiac or major aortic surgery between December 2015 and November 2017. We evaluated the validity of rSO2 by comparing it with ipsilateral jugular venous oxygen saturation (SjvO2). In HD and non-HD patients, rSO2 and SjvO2 showed a weak correlation (R2: 0.46 and 0.28 in HD and non-HD patients, respectively). Bland-Altman analysis revealed that bias (95% limits of agreement) of rSO2 compared to SjvO2 was - 19.2% ( - 41.7-3.3%) in HD patients and - 1.9% (- 19.3-15.5%) in non-HD ones. The large negative bias suggests that the rSO2 values measured using near-infrared spectroscopy substantially underestimate cerebral oxygenation in HD patients.