Lower Bicarbonate Level Risk Factor for Acute Kidney Injury

An increase in the risk of progression of kidney disease is associated with lower serum bicarbonate levels. It is unclear whether lower serum bicarbonate levels are associated with an increased risk of acute kidney injury (AKI). Jessica Kendrick, MD, and colleagues conducted an analysis to examine the association between lower serum bicarbonate levels and increased risk of AKI. Results were reported in the Journal of Nephrology [doi.org/10.1007/s40620-020-00747-8].

The analysis included 8393 patients from SPRINT (Systolic Blood Pressure Intervention Trial); eligible patients had baseline serum bicarbonate levels and complete data available. AKI was a predetermined adjudicated adverse event determined by hospital admission and discharge records with AKI as a recorded diagnosis.

Serum bicarbonate was examined in clinically significant cutoffs of ≤24, 25 to 28, and >28 mEq/L; 25 to 28 mEq/L was the reference group. The association between serum bicarbonate and development of AKI was assessed using Cox proportional hazard models.

At baseline, mean age of the cohort was 68 years, mean estimated glomerular filtration rate (eGFR) was 77 mL/min/1.73 m2, and mean serum bicarbonate level was 26.3 mEq/L. Participants with serum bicarbonate level ≤24 mEq/L were more likely to be male and to have lower eGFR at baseline.

At a median follow-up of 3.3 years, 293 participants developed AKI. More patients in the lower serum bicarbonate group developed AKI than those in the other two cohorts: 6.1% versus 2.8% in the 25 to 28 mEq/L group and 2.1% in the >28 mEq/L group. Following full adjustment, there was an association between bicarbonate level ≤24 mEq/L and a significantly increased risk of AKI compared with a bicarbonate level of 25 to 28 mEq/L (hazard ratio, 1.42; 95% confidence interval, 1.1-1.8).

In conclusion, the researchers said, “Lower serum bicarbonate levels are an independent risk factor for the development of AKI.”