Correlation between arterial blood pressure and oxygenation in tetralogy of Fallot

To examine the relationship between arterial blood pressure and oxygenation in patients undergoing complete surgical correction of tetralogy of Fallot, a retrospective study of 16 patients was first performed, looking at the correlation between mean arterial blood pressure (MAP) and arterial oxygen tension (PaO2). The correlation between phenylephrine-induced changes in MAP (delta MAP) and those in PaO2 (delta PaO2) was investigated prospectively in seven patients. In the retrospective study, there was a significant correlation between MAP and PaO2 (n = 66; r = 0.55; P less than 0.01), and most data points with a PaO2 less than 50 mm Hg were associated with a MAP less than 60 mm Hg. In the seven patients who received phenylephrine, 10 micrograms/kg, a significant correlation was found between delta MAP and delta PaO2 (n = 10; r = 0.95; P less than 0.01). These results suggest that in tetralogy of Fallot arterial blood pressure is a determinant of arterial oxygenation, and that the risk of serious hypoxia is significant when MAP is less than 60 mm Hg.