Acid-base disorders associated with serum electrolyte patterns in patients on hemodiafiltration

Area of Science:

• Nephrology
• Clinical Chemistry
• Dialysis Therapy

Background:

• Metabolic acidosis (MAC) is prevalent in dialysis patients, often linked to acid retention.
• The role of plasma ions in MAC pathogenesis and correction during dialysis remains unclear.
• Understanding MAC mechanisms is crucial for selecting appropriate dialysis solutions.

Purpose of the Study:

• To investigate the relationship between intradialytic acid-base status changes and serum electrolytes.
• To evaluate the causes of metabolic acidosis in patients undergoing hemodiafiltration.
• To assess the impact of dialysis on acid-base balance and electrolyte shifts.

Main Methods:

• Studied 68 patients undergoing post-dilution hemodiafiltration with a dialysate bicarbonate concentration of 32 mmol/L.
• Assessed acid-base disorders using both the traditional Siggaard-Anderson and modern Stewart approaches.
• Analyzed pre- and post-dialysis acid-base parameters and serum electrolytes.

Main Results:

• Pre-dialysis, 34% of patients had MAC, predominantly due to increased undetermined anions (UA(-)).
• Post-dialysis, 81% of patients developed metabolic alkalosis, characterized by a significant decrease in UA(-).
• Changes in base excess (ΔSBE) correlated with changes in UA(-) (ΔUA(-)), but not with changes in sodium-chloride difference (ΔDiff(NaCl)) or chloride (ΔCl(-)).

Conclusions:

• Metabolic acidosis in hemodiafiltration patients is mainly caused by acid retention and associated with higher protein intake.
• Sodium and chloride levels did not demonstrate a significant effect on the acid-base balance during dialysis.
• Post-dialysis alkalosis is common, resulting from excessive reduction of undetermined anions replaced by bicarbonate, indicating elimination of undesirable and endogenous anions.