[Evaluation of the aorta-to-radial artery pressure gradient in patients undergoing surgery with cardiopulmonary bypass.].

BACKGROUND AND OBJECTIVES Several studies have demonstrated a significant difference between the aortic and radial artery pressures in patients on cardiopulmonary bypass (CPB). The objectives of this study were to evaluate the behavior of the aorta-to-radial artery pressure gradient during myocardial revascularization (MR) with CPB and its correlation with the systemic vascular resistance. METHODS After approval by the Ethics Committee of the hospital, 16 patients undergoing MR with hypothermic CPB were studied. Systolic, diastolic and mean blood pressures were obtained at the root of the aorta and in the radial artery by using specific catheters. The cardiac output was obtained using a pulmonary artery catheter or from the CPB equipment, and the systemic vascular resistance index (SVRI) pre-CPB, at the beginning of CPB, after the last MR, at the end of the CPB, and post-CPB was calculated. Statistical analysis was done with Analysis of Variance for repeated measurements and Spearman correlation, and a level of significance of 0.05 was established. RESULTS After beginning CPB, the radial artery pressure was systematically lower than the aortic pressure by 3 to 5 mmHg. A significant correlation between the mean aorta-to-radial artery pressure gradient and SVRI was observed only in the last MR, corresponding to the rewarming of the patient (Rho = 0.67, p = 0.009). CONCLUSIONS Measurement of the radial artery pressure underestimated, systematically, the arterial pressure at the root of the aorta after CPB and the SVRI did not provide an accurate estimate of the magnitude of the aorta-to-radial artery pressure gradient.