Role of dialysis sodium gradient on intradialytic hypertension: an observational study.
BACKGROUND
The causes of intradialytic hypertension (IDHyper) are not well understood and this condition can complicate the clinical management of hemodialysis (HD) patients.


OBJECTIVE
To evaluate the potential role of intradialytic sodium gradient (NaG) on blood pressure values and IDHyper during HD.


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.


METHODS
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, Kt/V 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 (ΔSBP) (post-HD SBP - pre-HD SBP). IDHyper was defined as ΔSBP >0. A significant direct correlation was found between NaG and ΔSBP (p < 0.0001) and multiple regression analysis with ΔSBP as dependent variable confirmed the strong correlation with NaG (p < 0.00001). According to ΔSBP 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 ΔSBP is independently and strongly associated with the dialytic NaG. The more positive the NaG (net intradialytic Na gain), the more positive the ΔSBP and IDHyper.
Operative Unit of Nephrology, AO Spedali Civili di Brescia, and University of Brescia, Brescia, Italy.
Ezio
E
Movilli
Corrado
C
Camerini
Paola
P
Gaggia
Roberto
R
Zubani
Paolo
P
Feller
Patrizia
P
Poiatti
Alessandra
A
Pola
Orsola
O
Carli
Brunella
B
Valzorio
Giovanni
G
Cancarini
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D003430:Cross-Sectional Studies; D005260:Female; D015312:Hemodialysis Solutions / Q000737:chemistry*; D006801:Humans; D006973:Hypertension / Q000209:etiology* / Q000517:prevention & control*; D007676:Kidney Failure, Chronic / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood; D012044:Regression Analysis; D006435:Renal Dialysis / Q000009:adverse effects* / Q000379:methods*; D012964:Sodium / Q000097:blood*
D015312:Hemodialysis Solutions; D012964:Sodium; D011188:Potassium