A client with type 1 diabetes presents with polyuria, polydipsia, nausea, vomiting, and Kussmaul respirations. Which acid-base disturbance is most likely?

• A. Respiratory acidosis
• B. Metabolic acidosis with an increased anion gap
• C. Metabolic alkalosis
• D. Normal anion gap metabolic acidosis

Answer: (B)

This scenario points to diabetic ketoacidosis, which produces a metabolic acidosis with an increased anion gap. In type 1 diabetes without enough insulin, the body can’t use glucose effectively, so it begins breaking down fats for fuel. That fat breakdown releases ketone bodies, which are acids. These ketoacids accumulate in the blood, lowering the bicarbonate buffering capacity and causing metabolic acidosis. The body responds by breathing more deeply and rapidly (Kussmaul respirations) to blow off CO2, a sign of metabolic acidosis with respiratory compensation.

The presence of polyuria and polydipsia fits with severe hyperglycemia and osmotic diuresis seen in DKA, while nausea and vomiting are common symptoms of the same metabolic state. The key lab pattern here is a decreased bicarbonate with an elevated anion gap, reflecting the extra unmeasured anions (the ketoacids) in the bloodstream.

This is distinct from respiratory acidosis, which would come from CO2 retention and hypoventilation, not the deep, compensatory breathing seen here. It’s also not metabolic alkalosis, which would raise the blood pH and usually involve hypoventilation, nor is it normal anion gap metabolic acidosis, which would involve a normal anion gap despite acidosis (less consistent with DKA).