The adjustment of post dialytic dry weight based on non-invasive measurement of extracellular fluid and blood volumes

One of the major problems in the clinical practice of hemodialysis is an incorrect estimation of post dialytic (PD) dry weight. Underestimation of dry weight leads to hypovolemia induced hypotension, and overestimation to hypertension, pulmonary edema, and left ventricular hypertrophy. Because of the insensitivity of clinical variables to estimate dry weight, a more accurate technique is warranted. For this purpose and for the continuous surveillance of changes in blood volume (BV) during hemodialysis, two non-invasive techniques were applied. Based on post dialytically obtained extracellular fluid volume (EFV) values, measured by means of a conductivity method, 30 stable hemodialysis patients were divided into three groups for further analysis: de- (n = 9), normo- (n = 15), and overhydrated (n = 6). Using an on-line optical reflection method, changes in BV were measured continuously during therapy. Mean BV decrease, corrected for UF, differed slightly between the three groups (0 = 1.84 +/- 2.06, N = 3.20 +/- 1.80, D = 4.20 +/- 1.60 %/L). However, eight hypotensive episodes occurred in group D versus none in groups N and O. These hypotensive episodes were characterized by a greater reduction of BV--corrected for ultrafiltration--from the start of treatment until the moment of hypotension (6.96 +/- 2.21 %/L), compared with the 22 non hypotensive controls (2.16 +/- 2.01 %/L, p < 0.001). Based on the PD EFV dry weight of the overhydrated and dehydrated patients was decreased and increased, respectively, by 500 g after each session, until PD EFV was within normal bounds.(ABSTRACT TRUNCATED AT 250 WORDS)