Relationship between serum total carbon dioxide concentration and bicarbonate concentration in patients undergoing hemodialysis

Metabolic Acidosis in Chronic Kidney Disease: Pathogenesis, Clinical Consequences, and Treatment

The kidneys play an important role in regulating the acid-base balance. Metabolic acidosis is common in chronic kidney disease (CKD) patients and can lead to poor outcomes, such as bone demineralization, muscle mass loss, and worsening of renal function. Metabolic acidosis is usually approached with evaluating the serum bicarbonate levels but should be assessed by counting blood pH. Current guidelines recommend oral bicarbonate supplementation to maintain the serum bicarbonate levels within the normal range. However, a slow decline in the glomerular filtration rate might occur, even though the serum bicarbonate levels were in the normal range. Because the serum bicarbonate levels decrease when metabolic acidosis advances, other biomarkers are necessary to indicate acid retention for early diagnosis of metabolic acidosis. For this, urine citrate and ammonium excretion may be used to follow the course of CKD patients. Metabolic acidosis can be treated with an increased fruit and vegetable intake and oral alkali supplementation. Previous studies have suggested that administration of oral sodium bicarbonate may preserve kidney function without significant increases in blood pressure and body weight. Veverimer, a non-absorbed, counterion-free, polymeric drug, is emerging to treat metabolic acidosis, but further researches are awaited. Further studies are also needed to clarify the target therapeutic range of serum bicarbonate and the drugs used for metabolic acidosis.

Relationship Between Serum Total Carbon Dioxide Concentration and Bicarbonate Concentration in Patients Undergoing Peritoneal Dialysis

Background

Few studies have assessed the relationship between serum total carbon dioxide (CO₂) and bicarbonate ion (HCO₃⁻) concentration in patients undergoing peritoneal dialysis. We determined the agreement between serum total CO₂ and HCO₃⁻ concentration and the diagnostic accuracy of serum total CO₂ for the prediction of low (HCO₃⁻ <24 mEq/L) and high (HCO₃⁻ ≥24 mEq/L) bicarbonate concentrations in patients on peritoneal dialysis.

Methods

We collected 245 samples of venous blood from 51 patients on peritoneal dialysis. Independent factors that correlated with the HCO₃⁻ concentration were analyzed using multiple linear regression analysis. The diagnostic accuracy of serum total CO₂ was evaluated by receiver operating characteristic (ROC) curve analysis and a 2×2 table. Agreement between serum total CO₂ and HCO₃⁻ concentration was assessed by Bland-Altman analysis.

Results

Serum total CO₂ was independently correlated with HCO₃⁻ concentration (β = 0.354, p < 0.001). The area under the curve of serum total CO₂ for the identification of low and high bicarbonate concentrations was 0.909. The diagnostic accuracy of serum total CO₂ for the prediction of low and high bicarbonate concentrations was: sensitivity, 91.5%; specificity, 74.7%; positive predictive value, 53.5%; negative predictive value, 96.5%; and accuracy, 78.8%. Bland-Altman analysis showed a moderate agreement between serum total CO₂ and HCO₃⁻ concentration.

Conclusion

Serum total CO₂ correlated closely with the HCO₃⁻ concentration in patients undergoing peritoneal dialysis. Serum total CO₂ might be useful for predicting low and high bicarbonate in peritoneal dialysis patients.