Acid-base assessment of patients receiving hemodialysis. What are our management goals?

Acid-base assessment of patients receiving conventional hemodialysis (HD) has been based solely on predialysis serum [total CO₂ ], and treatment is currently driven by the KDOQI guideline from 2000. This guideline was directed solely at minimizing metabolic acidosis and thereby improving bone and muscle metabolism. In 2000, no data were available to assess the effects of acid-base status on morbidity and mortality. Since then, new data have emerged from several large cohort studies about the association between variations in predialysis serum [total CO₂ ], as well as blood pH, and morbidity and mortality risk. These studies have shown increased risk not only with very low predialysis [total CO₂ ] values, but also with predialysis alkaline pH and very high predialysis serum [total CO₂ ] values. At present, our major concern is not for patients with metabolic acidosis, but rather for the growing numbers of patients with metabolic alkalosis. This review discusses the controversies around assessing and treating acid-base status in HD patients, and recommends a practical approach based on the results of these recent studies. The new approach provides recommendations for patients both with very low and very high predialysis serum [total CO₂ ] values.