Lactic acidosis presenting as acute respiratory failure.

Two patients with chronic obstructive pulmonary disease and chronic respiratory failure who developed acute lactic acidosis are described. The initial arterial blood gas values in both patients had the pattern of acute respiratory failure with no metabolic disturbance. It was the calculation of the "anion gap" that provided the clue to the presence of metabolic acidosis, which was then confirmed with the measurement of serum lactate. We emphasize that complete laboratory data and clinical information may be essential for accurate diagnosis and understanding of mixed acid-base disturbances and, hence, for initiation of appropriate treatment.