Pseudohypobicarbonatemia in a Patient Presenting with Suspected Diabetic Ketoacidosis

Objective: In the diagnosis of acid-base disturbances, an accurate assessment of bicarbonate is essential. It can be determined by measurement of a urea and electrolyte panel or calculated on a blood gas analysis. Discrepancies in these two values can be due to endogenous interferents. We report a case of pseudohypobicarbonatemia suspected due to hypertriglyceridemia, despite lipidemia being within the reported acceptable range for the analyzer. Methods: We detail the hospital course of a 33-year-old man who presented with presumed diabetic ketoacidosis based on new-onset hyperglycemia, positive ketones, and measured bicarbonate in the range 9 to 16 mmol/L. The latter caused the calculation of anion gap metabolic acidosis. We review bicarbonate metabolism and technical aspects of its measurement. Further, we review additional reports and research pertinent to our patient's diagnostic dilemma. Results: Based on our patient's initial presentation, he was placed on an insulin drip for approximately 30 hours. During the hospital course, his calculated bicarbonate levels from blood gases ranged from 20 to 26 mmol/L, significantly higher than the measured bicarbonates. On the insulin drip, his triglyceride levels fell slightly and his measured bicarbonate levels increased to more closely mirror the values obtained on blood gas analysis but still varied by greater than expected. Posthospitalization, when his triglycerides were near normal, his measured bicarbonate was normal. Conclusion: The current case highlights the importance of recognizing discordant measured and calculated bicarbonate and that endogenous interferents can lead to falsely low or high carbon dioxide values.