Abstract: Objective The aim of this study was to investigate the relationship between serum renin-angiotensin-aldosterone system (RAAS) level and the variation of intradialytic blood pressure in maintenance hemodialysis patients during dialysis sessions. Methods Fifty-three MHD patients were enrolled in this trial.
Fifteen of them had intradialytic hypotension, 20 of them had intradialytic hypertension, and the rest of the patients had intradialytic stable BP. Plasma levels of angiotensin- II (Ang-II), aldosterone (ALD), angiotensinconverting enzyme (ACE), endothelin-1 (ET-1), and nitric oxide (NO) were measured. Results Serum Ang-II, ACE, and ALD were significantly higher in intradialytic hypertension group than in intradialytic stable BP group (97.269±47.256 ng/L vs. (75.334±27.205)ng/L, t=-1.727, P=0.018 for Ang-II; (37.022±9.482)U/L vs. (25.415 ± 10.215)U/L, t=- 3.618, P=0.023 for ACE; [(176.469 ± 67.070)ng/L vs. (124.093 ± 42.642)ng/L, t=-2.901, P=0.007 for ALD]. Serum levels of Ang-II, ACE and ALD were higher in intradialytic hypotension group than in intradialytic stable BP group, but only ALD level was statistically significant [(163.034±53.266) ng/L vs. (124.093 ± 42.642)ng/L, t=2.286, P=0.030]. Serum NO was the highest in intradialytic stable BP group (74.371±27.650) μmol/L, followed by intradialytic hypotension group (65.566±16.785) μmol/L and intradialytic hypertension group [(60.430 ± 17.906) μmol/L; F=2.024, P=0.143]. In contrast, serum ET-1 was the lowest in intradialytic stable BP group (3.650 ± 1.291 pg/ml), followed by intradialytic hypotension group (4.313±1.414 pg/ml) and intradialytic hypertension group [(4.819±1.938) pg/ml; F=2.539, P=0.089]; serum ET- 1 was significantly lower in intradialytic stable BP group than in intradialytic hypertension group (t=-2.208, P=0.034). NO/ET-1 ratio was significantly lower in intradialytic hypotension group and intradialytic hypertension group than in intradialytic stable BP group (15.756±3.257 vs. 20.614±7.485, t=-2.486, P=0.026 between intradialytic hypotension group and intradialytic stable BP group; 14.035±4.845 vs. 20.614±7.485, t= 3.178, P=0.003 between intradialytic hypertension group and intradialytic stable BP group). Multiple stepwise regression analysis found that interdialysis weight gain (IDWG; B=1.482, P=0.001), cardiac complications (B= 4.578, P=0.001), diabetes mellitus (B=3.038, P=0.024), gender (B=- 2.183, P=0.035), and dialysis vintage (B= -0.167, P=0.018) correlated with intradialytic BP changes, but serum RAAS parameters and NO/ET-1 ratio did not correlated with intradialytic BP changes. Conclusion Activation of RAAS and endothelial dysfunction relate to the variation of intradialytic blood pressure in MHD patients during dialysis sessions. Fluid overload may play a role in the pathogenesis of intradialytic hypertension. IDWG, diabetes mellitus, gender, cardiac complications and dialysis vintage affect the level of blood pressure during dialysis sessions.

Key words: Hemodialysis, Variation of Intradialytic Blood Pressure, Renin- angiotensin- aldosteronesystem