Role of Lung Ultrasound in Adjusting Ultrafiltration Volume in Hemodialysis Patients

Abstract

Chronic fluid over-hydration is common in dialysis patients. It is associated with mortality and cardiovascular events. Optimal methods for adjusting fluid volume status and ideal dry weight remain uncertain. The purpose of this study was to evaluate the usefulness of ultrasound in quantifying body water. In 35 hemodialysis patients, we performed ultrasound of the chest, pre-tibial skin tissue thickness (TT), heart and inferior vena cava (IVC) before and after dialysis. We compared B-line scores of lungs, IVC diameters and cardiac functions in pre-dialysis and post-dialysis groups. We then estimated the correlations between ultrasound parameters and ultrafiltration volumes. Ultrafiltration parameters were adjusted prospectively for subsequent dialysis. As a result, both extravascular and intravascular water decreased during ultrafiltration. The median numbers of B-line scores (10 [0-42] vs. 4 [0-30]; p < 0.001); mitral valve blood flow velocities E (0.83 ± 0.23 m/s vs. 0.70 ± 0.20 m/s; p < 0.001), A (0.93 ± 0.28 vs. 0.89 ± 0.23 m/s; p < 0.001) and E/e' (12.47 ± 4.92 vs. 10.37 ± 4.0; p < 0.001); IVC diameters at end-expiration (17.51 ± 3.33 mm vs. 14.26 ± 3.45 mm; p < 0.001); and right pre-tibial TT (2.86 ± 1.36 mm vs. 2.43 ± 1.24 mm; p < 0.001) decreased during dialysis. Ultrafiltration volume was most associated with B-line score (adjusting for age and sex) (β = -3.340; p = 0.003). In addition, the B-line score after dialysis was significantly associated with left ventricular ejection fraction (r = -0.393; p = 0.019) and TT (r = -0.447; p = 0.007). Ultrafiltration volume was prospectively increased then if the B-line score was >6 in the previous dialysis. All patients tolerated the protocol well without any symptoms. Ultrafiltration volume was most associated with lung water, reflected by variation in B-line score. It was not associated with cardiac function, IVC diameter, IVC collapse rate or TT. Lung ultrasound is a useful imaging tool for dialysis patients.

Keywords: Dry weight; Extravascular lung water; Hemodialysis; Lung ultrasound; Ultrafiltration.