Minimal safe arterial blood flow during selective antegrade cerebral perfusion at 20° centigrade

Selective antegrade cerebral perfusion (SACP) enables surgery on the aortic arch, where cerebral ischemia may cause neurologic sequels. This study aims to identify the minimum arterial flow level to maintain adequate cerebral perfusion during SACP in deep hypothermia in the pig.

Two groups of pigs were subjected to SACP at 20(°)C α-stat. In group 1 (n = 6), flow was stepwise adjusted from 8-6-4-2-8 mL · kg(-1) · min(-1) and in group 2 (n = 5), flow was kept constant at 6 mL · kg(-1) · min(-1). Magnetic resonance imaging and spectroscopy were performed at each flow level together with hemodynamic monitoring and blood gas analysis. The biochemical marker of cerebral damage protein S100β was measured in peripheral blood.

Decreased mixed venous oxygen saturation and increased lactate in magnetic resonance spectroscopy was seen as a sign of anaerobic metabolism below 6 mL · kg(-1) · min(-1). No ischemic damage was seen on diffusion-weighted imaging, but the concentrations of S100β were significantly elevated in group 1 compared with group 2 at the end of the experiment (p < 0.05). Perfusion-weighted imaging showed coherence between flow setting and cerebral perfusion, increase of blood volume across time, and regional differences in perfusion during SACP.

The findings suggest an ischemic threshold close to 6 mL · kg(-1) · min(-1) in the present model. Regional differences in perfusion during SACP may be of pathogenic importance to focal cerebral ischemia.