A 14-year-old boy with insulin-dependent diabetes presents with symptoms including polyuria and generalized weakness. What is his most likely arterial blood gas (ABG) result indicating diabetic ketoacidosis?

In the context of diabetic ketoacidosis (DKA), the arterial blood gas (ABG) results typically display a specific pattern indicative of metabolic acidosis, which is a hallmark of DKA. In this case, the correct choice presents a pH of 7.20, a low bicarbonate (HCO3-) level of 13, and a pCO2 of 20.

The pH of 7.20 indicates acidemia, as normal arterial blood pH is typically between 7.35 and 7.45. The low bicarbonate level suggests that there is a significant metabolic acidosis occurring, which is consistent with DKA since keto acids accumulate in the blood due to the breakdown of fats for energy due to insulin deficiency. A bicarbonate level below 15 mEq/L is often seen in DKA and is a critical marker in diagnosing this condition.

The pCO2 of 20 indicates a compensatory respiratory alkalosis, which often occurs in DKA as the body attempts to correct the acidosis by hyperventilating (Kussmaul respirations). The low pCO2 reflects the respiratory compensation rather than the primary disturbance.

In summary, the combination of a significantly low pH, reduced