Factors affecting the difference between radial and femoral arteril pressure after cardiopulmonary bypass in patients undergoing valvular replacement

Background: After cardiopulmonary bypass (CPB), the radial arterial pressure is often lower than that of the femoral artery. If this difference is overlooked, the patients might be treated with unnecessary vasoconstrictors or inotropes. However, the exact etiology or mechanism of this discrepancy is not known. If a patients group with the risk of a high pressure gradient after CPB could be predicted, the femoral arterial pressure from pre-CPB period might be monitored in order to not be inadequately managed after weaning from CPB. We studied the predicting factors of this phenomenon in patients undergoing a valvular replacement. Methods: One hundred patients undergoing valvular replacement were included in this study. The radial and femoral arterial pressures were measured in the same monitoring system during entire procedure of the operation. The radial to femoral arterial pressure ratio (R/F) was calculated. Demographic data and hemodynamic variables after induction of anesthesia were studied using correlation analysis to assess which data could be associated with R/F. A best predictive model was developed with stepwise multiple linear regression analysis. Results: Correlation analysis showed that age, preoperative ejection fraction (EF), and cardiac index after induction were statistically significant. A predictive model was developed including age and preoperative EF. The regression equation is R/F = 86.249 - (0.294 × age) + (0.329 × preoperative EF). Conclusions: It could be predicted in the patients with old age or low preoperative ejection fraction that radial arterial pressure might be lower than that of femoral artery in a valvular replacement operation.ope