Pseudo-anion gap metabolic acidosis from severe hypertriglyceridemia corrected by plasma exchange


Falsely low or even unmeasurable serum bicarbonate has been described in patients with severe hypertriglyceridemia or paraproteinemia. This phenomenon, known as pseudo-hypobicarbonatemia, is believed to be due to interference by these components when the commonly used enzymatic assay is utilized for serum bicarbonate measurement. The calculated bicarbonate derived from blood gas machines is not affected. This can lead to a misdiagnosis of a severe anion gap metabolic acidosis along with an extensive and expensive work-up.

We review a series of 5 patients with severe hypertriglyceridemia who presented with pseudo-hypobicarbonatemia and an elevated anion gap metabolic acidosis. Membrane-based therapeutic plasma exchange was utilized.

Following aggressive lowering of the triglycerides, there was an immediate resolution of the pseudo-hypobicarbonatemia and anion gap metabolic acidosis.

Recognition of lipemic serum in the setting of an otherwise unexplained anion gap metabolic acidosis should prompt the clinician to obtain a blood gas sample for true determination of the acid-base status. Doing so may avoid an extensive and expensive metabolic work-up.