Intra- and post-dialytic changes of haemoglobin concentrations in non-anaemic haemodialysis patients

Background. Non-anaemic haemodialysis (HD) patients are potentially more prone to the adverse effects of ultrafiltration-induced haemoconcentration. No study, however, has assessed the effects of dialytic session on haemoglobin (Hb) levels in these patients. Methods. The levels of Hb and total protein before, at the end (TO) and up to 120min(T120) after the third HD session of the week were compared in non-anaemic (Hb > 13 g/dl, n = 14, NOR) and anaemic (Hb = 11- 12 g/dl, n = 18, LOW) HD patients. Results. The intradialytic weight loss was similar in the two groups (4.0 ± 0.9 and 4.1 ± 0.9% body weight). During the treatment, Hb levels increased to the same extent in both groups (from 14.4 ± 1.2 to 16.3 ± 1.9 g/dl in NOR, and from 11.4 ± 0.8 to 12.7 ± 0.9 g/dl in LOW) in the presence, presumably, of a smaller plasma volume in NOR, whereas the increment of total protein was greater in NOR (from 7.1 ± 0.2 to 9.6 ± 0.5 g/dl) than in LOW (from 7.3 ± 0.6 to 8.7 ± 0.8 g/dl) (P <0.0001). At T120, the Hb decline in NOR was almost double that measured in LOW (-9.2 ± 3.0 vs -4.7 ± 2.4%, P <0.001). Consequently, Hb concentration did not differ from the pre-dialytic value in NOR (P=0.10), but persisted higher in LOW (P <0.005). The extent of the postdialytic decrement of Hb was inversely related to the total protein values at TO (r = -0.547, P=0.0012). Conclusions. This study indicates that in NOR: (i) the extent of intradialytic increment of Hb is limited by a greater intradialytic plasma refilling; (ii) the greater plasma refilling persists after the end of dialysis, with the restoration of pre-dialytic Hb levels within the initial 2h; and (iii) the force driving this phenomenon resides mainly in the larger changes of total protein concentration.