Comparison of the non-invasive methods estimating dry weight in hemodialysis patients.

Background: The treatment of deranged water homeostasis of hemodialysis (HD) patients needs focusing on an accurate assessment of dry weight (DW). However, the correct estimation of post-dialysis DW is still a problem. Echocardiography of inferior caval vein diameter (ICVD) was recently considered as a reliable technique to estimate DWs of HD patients, whereas conductivity measurements and biochemical parameters remain controversial. In this study, we aimed to compare the noninvasive methods estimating DW in HD patients.

Methods: We enrolled 60 patients: 30 hypervolemic (HV) (12 M, 18 F, with a mean age of 41.9 +/- 13.6 years, mean HD duration of 38 +/- 45 months) and 30 normovolemic (NV) patients (19 M, 11 F, with a mean age of 42.2 +/- 14 years, mean HD duration of 62 +/- 51.5 months) according to clinical sign and symptoms as well as the findings on chest x-ray. Furthermore, the DWs of patients were evaluated in post-HD period in terms of echocardiography parameters [ICVD and collapse index (CI) determined by Cheriex], plasma ANP (pANP) levels (RIA), and total body water (TBW) by bioelectrical impedance (BEI).

Results: Forty-one of 60 patients had hypervolemic findings (68%) and 19 patients had normovolemia (32%) according to echocardiography parameters. Determination of "hypervolemia" by clinical acumen and pANP levels were not reliable, especially negative predictive values were lower as follows: sensitivity, specificity, positive predictive value, negative predictive values of clinical acumen and pANP levels: 63%, 69%, 87%, 50%, and 67%, 59%, 79%, 43%, respectively. TBW established by BEI did not correlate with ICVD and CI after HD (p > 0.05). The TBW of HV group according to echocardiography parameters was greater than NV group, but the difference was not statistically significant (27.4 +/- 6.6 kg versus 26.4 +/- 5.8 kg, respectively, p > 0.05). However, there was not any difference in the divided BSA values (1.58 +/- 0.2 kg/m2 versus 1.60 +/- 0.2 kg/m2, respectively, p > 0.05). Hypertension was seen in 37 (90%) of the echocardiographically hypervolemic patients, and the blood pressure was kept under control by previously given medication in only 7 (19%) patients. After the dry weight of the patients was corrected echocardiographically to normal limits, the blood pressure of 31 patients (86%) was normalized without antihypertensive treatment, but only in 6 patients remained the necessity of antihypertensive treatment. In addition, in 8 of 11 normotensive patients using antihypertensive drugs, assessment of their clinical and radiological findings showed normovolemia but ICVD > 11.5 mm/m2; however, the need for antihypertensive drugs disappeared when the ICVD reduced to 8-11.5/m2.

Conclusions: Clinical and radiological assessment, pANP levels, and TBW established by BEI appeared to be less valuable in interpreting DW's of HD patients. In accordance with the literature, echocardiography findings have proven to be reliable, and they are important noninvasive tools that can establish an effective and rational antihypertensive treatment.