Spinal cord regional perfusion at 3 levels. Data are presented as absolute values. Left: proximal injections; middle: distal injections; right: total perfusion. Microsphere injections during the 2 first time points were performed via left atrium. CPB: cardiopulmonary bypass; CSF ×3: increase of cerebrospinal fluid pressure from baseline; DP: distal perfusion; X-clamp: aortic cross-clamping.