Cerebral oxygen saturation and blood flow during liver transplantation

After reperfusion of a liver graft, transcranial Doppler determined middle cerebral artery flow velocity, increases more than expected from the arterial carbon dioxide tension (Paco(2)). We evaluated if this indication of cerebral hyperperfusion is reflected in the jugular oxygen saturation (Sjo(2)) (n = 31) and oxygen saturation (Sco(2)) (near-infrared spectrophotometry, n = 22). From the dissection phase to the anhepatic phase Sjo(2) 71.0% (range 62.3%-78.5%), Sco(2) 70% (range 65%-77%), and Paco(2) 34.9 mm Hg (range 30.8-38.3) remained statistically unchanged. In contrast during the early reperfusion phase, Sjo(2) increased to 77.0% (71.4%-83.0%) (P < 0.01) and the Sco(2) to 75% (68%-80%)(P < 0.05) as Paco(2) increased to 37.5 mm Hg (34.8-41.9)(P < 0.001). Notably, Sjo(2) also increased at reperfusion from 71.6% (66.5%-78.0% mm Hg) to 80.0% (76.8%-84.8%) in the four patients in whom Paco(2) decreased at reperfusion from 37.6 mm Hg (36.8-39.5) to 34.0 mm Hg (32.3-36.8). If the changes in Sjo(2) after reperfusion of the grafted liver should be explained as a reflection of changes in cerebral blood flow, in response to Paco(2), it would indicate a highly accentuated CO2 reactivity of 13%/mm Hg. The results support that cerebral blood flow and, in turn, oxygenation increase after reperfusion because the grafted liver liberates a vasodilating substance(s).