Plasma Exchange Transfusion for Refractory High Anion Gap Metabolic Acidosis

High anion gap metabolic acidosis (HAGMA) is common in critical illness. The GOLD MARK mnemonic summarizes conventional etiologies, but a subset of cases remain unexplained and refractory to standard therapy.

We report two ICU patients with severe, refractory HAGMA. Case 1 was a 67-year-old man with profound lactic acidosis and an anion gap of 46 mmol/L, unresponsive to CRRT and supportive care. Case 2 was a 50-year-old man with cardiogenic shock who developed persistent HAGMA despite CRRT. In both cases, metabolic workup excluded standard etiologies. Laboratory testing revealed abnormalities in amino acids and acylcarnitines. In Case 1, low albumin electrophoresis was observed despite normal serum albumin levels. Each patient underwent three sessions of plasma exchange with albumin replacement, resulting in rapid and sustained resolution of metabolic acidosis.

These cases highlight plasma exchange as a potential rescue therapy for refractory HAGMA, possibly mediated by protein-bound acids. While causality cannot be established, our findings support further study into the role of plasma exchange in unexplained or treatment-resistant HAGMA.