Role of Dialysis Sodium Gradient on Intradialytic Hypertension: An Observational Study

Introduction:The causes of intradialytic hypertension (IDHyper) are not well understood and this condition can complicate the clinical management of hemodialysis (HD) patients. Aim: To evaluate the potential role of intradialytic sodium gradient (NaG) on blood pressure values and IDHyper during HD. Patients and Methods: 206 prevalent HD patients on 3 times weekly HD treatment for at least 6 months (dialytic vintage 6-240 months) followed at our institution were studied. Mean age was 68 14 years, 129 were men. For 2 consecutive months (24 HD sessions) after the start of observation, the following variables were evaluated in predialysis after the long interdialysis interval: pre-HD plasma sodium (pNa, mmol/l) and potassium (pK, mmol/l) concentrations (mean value of 8 determinations), pre- and post-HD systolic (SBP, mm Hg) and diastolic (DBP, mm Hg) blood pressure, dry body weight (dBW, kg), interdialytic weight gain (IDWG, kg), ultrafiltration rate (UFR, ml/kg/h), dialysis dose (Kt/V), protein catabolic rate (PCRn, g/kg/day), hemoglobin (Hb, g/dl). SBP, DBP,IDWG, UFR are the mean values of the 24 HD sessions. 76% of patients were on antihypertensive therapy, 171 patients were on bicarbonate HD, and 35 on HDF. Dialysate Na concentration was set at 140 mmol/l in all patients. Duration of HD and the blood and dialysate flow rate were kept constant during observation. Statistical Analysis: Data are expressed as mean +/- SD; linear and multiple regression analysis and t test for unpaired data were employed. Significant differences were defined as p < 0.05. Results: Pre-HD pNa was 138.1 +/- 2.3 mmol/l, pK 5.0 +/- 0.4 mmol/l, dBW 67 +/- 14 kg, IDWG 2.9 +/- 0.8 kg, UFR 11.2 +/- 3.7 ml/kg/h, KtN 1.43 +/- 0.18, PCRn 1.13 +/- 0.17 g/kg/day, and Hb 11.2 +/- 0.8 g/dl. Pre- and post-HD SBP values were 139 13 and 134 12 mm Hg (p < 0.0001); pre- and post-HD DBP did not change significantly. A dialysis Na gradient (NaG) (dialysate Na pre-HD pNa) was calculated, as well as the delta of SBP (Delta SBP) (post-HD SBP pre-HD SBP). IDHyper was defined as Delta SBP >0. A significant direct correlation was found between NaG and Delta SBP (p < 0.0001) and multiple regression analysis with ASBP as dependent variable confirmed the strong correlation with NaG (p < 0.00001). According to Delta SBP behavior, 171 patients (83%) had a decrease or no change in post-HD SBP (group 1; no IDHyper); 35 patients (17%) increased their post-HD SBP (group 2; IDHyper). NaG values were significantly greater in patients in group 2 (group 1:1.5 +/- 2.2 vs. group 2:3.3 +/- 2.5, p < 0.0001). Conclusions: This study shows that the intradialytic ASBP is independently and strongly associated with the dialytic NaG. The more positive the NaG (net intradialytic Na gain), the more positive the Delta SBP and IDHyper. (C) 2013 S. Karger AG, Basel