Acid-base balance disturbances in plasma exchange depend on the replacement fluid used

Metabolic alkalosis occurs as a direct result of plasma exchange (PE) because of metabolism of citrate. However, we observed a decrease of serum pH and bicarbonate after PE when albumin was used as replacement fluid.

The acid-base balance in 2730 PEs using different replacement fluids (albumin, fresh-frozen plasma [FFP], or both) was measured, and absolute changes (Δ) in acid-base balance were compared. The frequency of adverse effects (AEs) before and after using prophylactic administration of sodium bicarbonate was compared.

A decrease of serum pH and bicarbonate was observed after PEs when albumin was used as replacement fluid (Δ pH = -0.06 ± 0.04; Δ bicarbonate = -4.03 ± 2.29 mmol/L; Δ base excess = -2.54 ± 3.82 mmol/L). An increase of serum pH and bicarbonate was observed after PEs when FFP was used as replacement fluid (Δ pH = +0.04 ± 0.05; Δ bicarbonate = +3.6 ± 3.68 mmol/L; Δ base excess = +1.62 ± 4.51 mmol/L). The prophylactic administration of sodium bicarbonate corrected partially the decrease of serum pH and bicarbonate after finishing PEs when albumin was used as replacement fluid (Δ pH = -0.04 ± 0.04; Δ bicarbonate = -3.1 ± 2.47 mmol/L; Δ base excess = -3.35 ± 3.06 mmol/L). The frequency of AEs after using prophylactic administration of sodium bicarbonate was lower in comparison with the frequency of AEs before using prophylactic administration of sodium bicarbonate (2.0% vs. 4.8%; p < 0.001).

A decrease of serum pH and bicarbonate appeared in patients after PEs when albumin was used as replacement fluid; it was corrected partially with prophylactic administration of sodium bicarbonate, and it was associated with fewer AEs.