119 Proposal of a new technique for evaluating the total liver blood flow volume during pregnancy by doppler sonography

Abstract

Introduction Estimation of the total liver blood flow volume by Doppler sonography during pregnancy might be a promising tool in the assessment of patients with severe PE/HELLP syndrome. The usual Doppler technique does not individual variations in vessel’s diameter. We believe this can be an important source of measurement bias. Objective To propose an improvement in the Doppler technique for evaluation of hepatic total blood flow during pregnancy. Method 55 normal pregnant women were included and signed informed consent. They were fasting for at least 6 h. The standard Doppler method of estimating flow volume does not consider variations in vessel’s diameter, the sample volume is set at 3,0 mm. We propose to measure the vessel’s diameter and to adjust the sample volume so that it occupies the entire vessel lumen. The volume flow should be calculated more accurately as the different speeds of the red blood cells are considered, instead of the speeds of the center of the vessel. Reproducibility was tested by interobserver and intraobserver variabilities. Two experienced examiners (A and B) performed all tests. Doppler sonography of the portal vein and the common hepatic artery were performed in the same woman three times by examiner A and three times by examiner B. Intraobserver variability was verified with the values obtained in the first and last measurements (supposed worst and best values). Variables analyzed were: portal vein (PV) flow volume A1 and A3, B1 and B3; common hepatic artery (CHA) flow volume A1 and A3, B1 and B3. Possible differences between the two observers were tested using the mean values obtained by each observer. We also calculated the intraclass correlation coefficient (ICC). Variables analyzed were: PV caliber A and B; CHA caliber A and B; Mean PV flow volume A and B; Mean CHA flow volume A and B. The statistical tests used for intra and interobserver variability testing were Stuart’s paired T-test, Pearson’s correlation coefficient and Blan–Altman’s plots of differences. Results Data was available for 50 women. We could not perform complete examination in 5 patients. Technical difficulties were mainly due to obesity, gas, and woman‘s intolerance to supine position. Women‘s mean age was 28y (18y–40y) and mean gestational age was 28w (20w–36w). We found low intraobserver and interobserver variability as demonstrated by paired T test and correlation coefficients in table 1. ICC for observer 1 was 0.982 for PV FV and 0.997 for CHA FV. ICC for observer 2 was 0.984 for PV FV and 0.998 for CHA FV. Conclusion The improvement we propose for Doppler assessment of the total hepatic blood flow in pregnancy has good intra and interobserver reproducibility. These results encourages us to continue research and to propose this method as preffered in pregnancy.