Anti-hypertensive effect of low Na concentration (120 mEq/l) solution for CAPD patients

n patients undergoing continuous ambulatory peritoneal dialysis (CAPD), transperitoneal sodium (Na) flux plays a crucial role in the control of blood pressure (BP), as it determines the net Na balance of the patient. However, with the conventional solution, Na removal into the effluent greatly depends on the drained ultrafiltration (UF) volume, and this can hinder the success of adequate Na removal in some patients. Therefore, we developed a low Na concentration solution to increase Na removal through diffusion force, and studied the clinical effect of this solution in patients with Na overload. The composition of the low Na solution is as follows: Na: 120 mEq/l, Ca: 3.5 mEq/l, Mg: 0.5 mEq/l, Cl: 84 mEq/l, lactate: 40 mEq/l, glucose (G) and osmolality: 1.36% (322 mOsm/l) and 2.27% (372 mOsm/l), vol: 21. Nine patients (age: 43 ± 2 yr, oral Na intake 3.4 ± 0.3 g/day, mean arterial pressure: 123 ± 6 mmHg, drained UF volume: 918 ± 187 ml/day; mean ± SEM) were studied. Compared to the conventional solution (Na: 132 mEq/l), Na removal using the low Na solution (4 h dwell) was increased from -7.8 ± 8.7 to -2.3 ± 5.7 mEq in 1.36% G solution, and from 25.3 ± 3.1 to 35.4 ± 4.7 mEq (p < 0.05) in 2.26% G solution. Patients were switched from the conventional solution to the low Na solution, exchanging four times daily for up to 4 weeks. Two patients discontinued low Na solution before the study ended, due to overhydration and hyponatremia, the remaining seven cases showed no adverse symptoms. During the study, trans-peritoneal Na removal increased from 38.5 ± 25.8 to 85.0 ± 27.2 mEq/day (p < 0.001). No statistical changes were found either in body wt or in UF volume. However, a significant fall in BP was found in all cases. This study demonstrates that a solution with a lower Na concentration than the conventional solution, is effectively used to increase trans-peritoneal Na removal thus, controling hypertension in cases with Na overload.