Effect of Sodium Bicarbonate on Indicators of Volume Retention in Metabolic Acidosis After Kidney Transplantation: A Post-Hoc Analysis.

Rationale & Objective Metabolic acidosis is a frequent complication after kidney transplantation, commonly treated with sodium bicarbonate. However, concomitant sodium loading raises concerns about potential volume retention. This study aims to assess its impact on clinical and biochemical markers of volume retention, as its effects post-transplant remain insufficiently studied.Study Design Post-hoc analysis of a randomized, single-blinded, placebo-controlled multicenter trial (Preserve-Transplant Study).Setting & Participants Total of 240 kidney transplant recipients with metabolic acidosis were randomized 1:1 across 3 University hospitals in Switzerland.Intervention 1.5-4.5 g/day sodium bicarbonate or placebo for 24 months.Outcomes Primary outcomes included body weight, N-terminal prohormone of brain natriuretic peptide, plasma renin, plasma aldosterone, aldosterone-to-renin ratio (the latter 4 log-transformed), nocturnal systolic blood pressure dipping, and antihypertensive agent use. Secondary outcomes included the occurrence of hypertension, hospitalization due to uncontrolled hypertension or volume overload, and sodium and potassium balance over time.Analytical Approach Descriptive statistics and mixed-effects regression models.Results There was weak evidence for treatment effects in the sodium bicarbonate group compared with the placebo group regarding body weight (between-group difference [BGD]: 1.23 kg, 95% CI: -0.18 to 2.63; P = 0.09), no evidence for N-terminal prohormone of brain natriuretic peptide (BGD: -0.03, 95% CI: -0.21 to 0.16; P = 0.78), plasma renin (BGD: -0.12, 95% CI: -0.34 to 0.09; P = 0.26), and aldosterone-to-renin ratio (BGD: -0.05, 95% CI: -0.28 to 0.18; P = 0.69), whereas there was substantial evidence for a treatment effect on plasma aldosterone (BGD: -0.17, 95% CI: -0.3 to -0.05; P = 0.007), the latter 4 log-transformed. There was weak evidence for an increased chance of nocturnal systolic blood pressure dipping (OR: 2.28; 95% CI: 0.88 to 5.87; P = 0.09). The use of antihypertensives and diuretics remained similar in both groups. Weak evidence for higher serum sodium (BGD: 0.51 mEq/L, 95% CI: 0.08 to 0.94; P = 0.02) and strong evidence for higher log-transformed 24 hour-sodium excretion (BGD: 0.16, 95% CI: 0.07 to 0.26; P ≤ 0.001) in the sodium bicarbonate group were identified. There was no or weak evidence for treatment effects on other secondary outcomes. Subgroup analyses showed no major differential effects.Limitations Post-hoc analysis, mainly Caucasian study population.Conclusions Our findings did not provide clear evidence for unfavorable effects of sodium bicarbonate on volume retention. Further research is required to clarify risks.Trial Registration ClinicalTrials.gov (ID: NCT03102996).Many kidney transplant recipients develop metabolic acidosis because the transplanted kidney may not fully restore acid–base balance. Sodium bicarbonate is commonly used to correct this, but its associated sodium load raises concerns about fluid retention. This study compared long-term sodium bicarbonate use with placebo and evaluated signs of volume overload, including changes in body weight, blood markers linked to fluid regulation, blood pressure patterns, and the use of blood pressure medications. Moreover, hospitalizations related to uncontrolled blood pressure or fluid overload were studied. Overall, the results showed no clear evidence of harmful effects. Further research should confirm these findings.