Is Metabolic Acidosis an Additional Risk Factor for Worse Prognosis in Kidney Transplant Patients?

Background: Metabolic acidosis (MA) frequently occurs in patients after kidney transplantation (KTx). Results of both experimental and clinical studies suggest that MA may contribute to faster progression of chronic kidney disease (CKD). Data on such relationship in KTx patients are limited. The aim of this clinical, single center, retrospective, observational study was to assess the relationship between MA and both patients’ mortality and long term graft survival after KTx. Methods: Blood [HCO3-] was measured in 486 patients (290 male; 196 female) aged 48.2±12.0 years first time at least one year after KTx and subsequently patients were observed for 11 years. MA was defined as the blood [HCO3-] concentration lower than 22 mmol/L. Results: MA was diagnosed in 57 (12%) patients at baseline of the follow-up. The Kaplan-Meier curves analysis have shown that patients with MA reach endpoints of follow-up earlier (log-rank p=0.002 for death and p<0.001 for dialysis or retransplantation and for cumulative endpoint p<0.001). In KTx patients with MA the risk of starting dialysis therapy or retransplantation was significantly higher than in KTx patients without MA [RR=2.00 (1.42-2.82), p<0.001]. In KTx patients with MA the risk of death was significantly higher than in KTx patients without MA [RR=1.61 (1.01-2.55), p=0.04]. The multivariable Cox regression analysis model has shown that baseline eGFR (HR=0.95 (0.94-0.97), p<0.001) and blood [HCO3-] (HR=0.92 (0.86-0.99), p=0.03) were negative predictors for initiation of dialysis therapy. Age (HR=1.09 (1.05-1.12), p<0.001) and diabetes mellitus (HR=2.12 (1.17-3.88), p=0.01) were positive predictors and blood [HCO3-] (HR=0.88 (0.81-0.97), p=0.009) was a negative predictor for death. KTx patients with metabolic acidosis were characterized by more pronounced eGFR loss in comparison to KTx patients without metabolic acidosis (eGFR decrease 3.4 vs. 2.4 mL/min/1.73 m2/year, p=0.04). Conclusion: 1. Metabolic acidosis is an important risk factor for increased mortality and progression of graft failure in kidney transplant patients 2. The prospective interventional studies with correction of MA will provide information whether treatment of MA improves the survival of both patients and transplanted kidneys. Funding: Government Support – Non-U.S.