Use of lung ultrasonography to determine the accuracy of clinically estimated dry weight in chronic hemodialysis patients

Abstract

The use of lung ultrasound (LUS) to identify extravascular lung water has received increasing acceptance. Sonographic B-lines, discrete vertical lines that originate from the pleura, represent pulmonary edema and are correlated with the accumulation of fluid. The goal of this study was to evaluate the utility of LUS to determine the accuracy of prescribed dry weight (DW) in chronic hemodialysis (HD) patients and to ascertain the adequacy of fluid removal. LUS was scheduled to be performed pre- and post-HD in 20 patients. The HD prescription and DW challenge were done independent of the results of the LUS. The presence of B-lines was tabulated and compared to the intradialytic ultrafiltration parameters. Of the 20 patients, 3 did not exhibit B-lines at the first dialysis session. In regard to the other 17 patients, B-lines disappeared in 7 patients at the end of the HD session (mean B-lines 4.2-0). One patient was 0.3kg away from the prescribed dry weight, but the 6 patients were a mean of 1.7kg below DW. Of the remaining 10 patients, eight decreased but did not eliminate the B-lines (mean B-lines 15.5-3.8) and were a mean of 3.8kg below DW post-HD. Two patients who exhibited more cardiac insufficiency than initially recognized could not reach DW or eliminate the B-lines. Eight patients who had residual B-lines at the end of the first HD session had their DW re-estimated and had a second session. Two were able to eliminate the B-lines (mean 2.5-0) and reached a mean of 1.2kg below DW. Six did not eliminate the B-lines (mean 11.5-4.2) but were able to reach a mean of 0.6kg below DW. Correlation analysis showed a statistically significant correlation (P<0.05) between the intradialytic percent change in B-lines and the percent change in total body weight (r=0.40) and ultrafiltration rate (r=0.33). Seven of 10 patients with clear chest X-rays pre-HD exhibited B-lines. This study supports the hypothesis that reduction in B-lines during HD can provide accurate information regarding changes in pulmonary fluid content. Further, LUS is a valuable diagnostic tool for recognizing both the adequacy of fluid removal and the occurrence of error in the estimation of dry weight by usual clinical parameters.