Lower serum bicarbonate levels, even within the normal range, are strongly linked to risks of cardiovascular disease in chronic kidney disease (CKD), possibly by modifying vascular function. Prospective interventional trials with sodium bicarbonate (NaHCO3) are lacking.

We conducted a randomized, double-blind, placebo-controlled trial examining the effect of NaHCO3 on vascular function in 109 patients with CKD stage 3b-4 (eGFR 15-44 ml/min/1.73m2) with normal serum bicarbonate levels (22-27 mEq/L). Participants were randomized 1:1 to NaHCO3 or placebo at a dose of 0.5 mEq/LBW-kg/day for 12 months. The co-primary endpoints were change in brachial artery flow mediated dilation (FMD) and change in aortic pulse wave velocity (aPWV) over 12 months.

Ninety patients completed the study. After 12 months, plasma bicarbonate levels increased significantly in the NaHCO3 group compared to placebo (mean (SD) difference between groups 1.35 ± 2.1, p=0.003). NaHCO3 treatment did not result in a significant improvement in aPWV from baseline. NaHCO3 did result in a significant increase in FMD after 1 month, however this effect disappeared at 6 and 12 months. NaHCO3 resulted in a significant increase in 24-hour urine citrate and pH and a significant decrease in 24-hour urine ammonia. There was no significant change in left ventricular mass index, ejection fraction or eGFR with NaHCO3. NaHCO3 treatment was safe and well-tolerated with no significant changes in blood pressure, antihypertensive medication, weight, plasma calcium or potassium levels.

Our results do not support the use of NaHCO3 for vascular dysfunction in participants with CKD and normal serum bicarbonate levels.