Spline regression model fit lines of the hemoglobin volume (HVx) index during induced hypotension. Each piglet’s lower limit of autoregulation (LLA) is centered to zero on the x-axis, permitting comparison of each animal’s cerebral perfusion pressure (CPP) relative to LLA. HVx became more positive as CPP decreased below the LLA in (A) normothermic sham, (B) hypothermic sham, (C) normothermic post-arrest, and (D) hypothermic post-arrest piglets. (n = 8 per group). Spline regression analysis indicated that the slope of the relationship of HVx with CPP became significantly more negative below the LLA in normothermic sham (p = 0.022) and normothermic arrested groups (p = 0.006).