Receiver operator characteristic curve showing renal oxygen saturation at 24 h.

(a) Receiver operator characteristic curve showing renal oxygen saturation at 24 h acting as a moderate classifier of chronic renal function, measured by the serum BUN at day 28. The optimal sO2 cutoff value at 24 h to differentiate better from worse renal failure at day 28 was 71.59%, with an area under the curve is 0.825 (P = 0.008). (b) Measured in terms of the 24 h CCr at day 28, the optimal sO2 cutoff value at 24 h to differentiate mild from severe renal failure was 65.3%, with an area under the curve of 0.864 (P = 0.005). (c) Measured in terms of the relative renal volume, the optimal sO2 cutoff value at 24 h to differentiate mild from severe renal atrophy was 65.3%, with an area under the curve of 0.790 (P = 0.020).