Venous serum bicarbonate concentration predicts arterial pH in adults with diabetic ketoacidosis

The initial assessment of metabolic acidosis in subjects with diabetic ketoacidosis (DKA) is arterial blood gas analysis. This process is expensive, painful, and technically difficult. Furthermore, blood gas analysis may not be available in some facilities, especially in developing countries where DKA-associated morbidity and mortality remain high. Therefore, we investigated the utility of venous bicarbonate concentration obtained from a basic metabolic panel in predicting arterial pH in adults with DKA.

We performed a retrospective analysis of clinical and biochemical data of 396 adults admitted to 2 community teaching hospitals with DKA. We determined the correlation between arterial pH and venous serum parameters. Using multiple logistic regression, we obtained a predictive formula for arterial pH from serum venous bicarbonate level.

The patient population was 59.0% male and had a mean age of 36.7 ± 13.3 years. We derived that arterial pH = 6.97 + (0.0163 x bicarbonate), and by applying this equation, we determined that serum venous bicarbonate concentration of ≤20.6 mEq/L predicted arterial pH ≤7.3 with over 95% sensitivity and 92% accuracy.

Venous serum bicarbonate obtained from the basic metabolic panel is an affordable and reliable way of estimating arterial pH in adults with DKA. Validation of this formula in a prospective study would offer a more accessible means of estimating metabolic acidosis in adults with DKA, especially in developing countries where DKA incidence and mortality remain high.