BACKGROUND: The radial artery pressure is known to differ from central arterial pressure in normal patients (distal pulse amplification) and in the early postcardiopulmonary bypass period. We assumed that there may be a change in the normal relationship between central and peripheral arterial pressure in patients with hepatic failure due to an arterio-venous shunt caused by vasodilation and a complex surgical procedure with major vessel clamping. This study was done to examine the adequacy of the radial artery as a site for blood pressure monitoring in liver transplantation (TPL). METHODS: We investigated when the pressure gradient developed and what mechanism could be responsible by comparing femoral to radial artery pressure in 11 patients undergoing liver transplantation. Radial and femoral artery pressures, systemic vascular resistance, cardiac output and temperature were compared during surgery in all 11 patients. Additionally measurements included pH, PaO2, PaCO2, central venous pressure, pulmonary artery pressure and mixed venous oxygen saturation. RESULTS: The femoral artery systolic pressure was higher than the corresponding radial artery pressures during the operation. Although not statistically significant, the radial mean and diastolic artery pressures were lower than corresponding the femoral artery pressure. CONCLUSIONS: Radial artery systolic pressures underestimate the femoral artery pressure when undergoing a liver TPL. Failure to recognize these effects on pressure recordings can lead to inappropriate patient management decisions.