Abstract
We investigated the effect of hemodilution on cerebral oxygen metabolism during mild hypothermic cardiopulmonary bypass (CPB) Methods: Seventeen adults scheduled for cardiac operations with CPB were studied. The percentage of oxygenated hemoglobin (% Oxy-Hb) measured by near-infrared spectroscopy and jugular bulb oxygen saturation (SJO2) were obtained at six points during CPB. Both parameters in low hematocrit points (group L: Ht<20) were compared with those in high hematocrit points (group H: Ht≥20). The influence of operative management parameters on cerebral oxygenation was calculated by regression analysis. Results: In group H and in group L, the % Oxy-Hb was 54.1±10.9 and 63.8±13.8, respectively and Sj02 was 66.9+15.3 and 74.5±16.7, respectively. Both parameters were higher in group H than in group L (p < 0.05). There were significant correlations between the % Oxy-Hb and Ht (r=0.53), PaCO2 (r=0.32) and Sj02 (r=0.54). It was observed that eighty five percent of the % Oxy-Hb over 60% in group L was maintained more than 35 mmHg in PaCO2, which suggested that although hemodilution had a detrimental effect on cerebral oxygen metabolism, impaired cerebral oxygenation during marked hemodilution was attenuated by high PaCO2.
