Vasotrac arterial blood pressure and direct arterial blood pressure monitoring during liver transplantation.

During liver transplantation two arterial catheters are often placed. The Vasotrac is a noninvasive monitor that provides radial arterial blood pressures by a tonometric method. We investigated whether the Vasotrac would be an accurate substitute for an arterial catheter by comparing Vasotrac blood pressures with simultaneous direct radial blood pressures recorded from the contralateral arm in 14 patients undergoing liver transplantation. Correlation between the two methods was calculated and a Bland-Altman analysis performed to assess agreement. A total of 6468 simultaneous measurements were made over a duration of 1.5-7.5 h per case. For mean arterial blood pressure 57% of Vasotrac measurements were within 10% of direct arterial measurement. Correlation (r) was 0.82. Vasotrac bias was +5.4 mm Hg and limits of agreement were +/-18.6 mm Hg. For systolic arterial blood pressure 65% of Vasotrac measurements were within 10% of direct arterial measurement. Correlation was 0.78. Vasotrac bias was +7.6 mm Hg and limits of agreement +/-25 mm Hg. For diastolic arterial blood pressure 57% of Vasotrac measurements were within 10% of direct arterial measurement. Correlation was 0.82. Vasotrac bias was +3.3 mm Hg and limits of agreement +/-15 mm Hg. We conclude that the Vasotrac is not adequately accurate to substitute for direct arterial blood pressure monitoring in liver transplantation.