A 72-year-old male with diabetes mellitus is evaluated in the emergency room because of lethargy, disorientation, and long, deep breaths (Kussmaul respirations). Initial chemistries on venous blood demonstrate high glucose at 380 mg/dL (normal up to 120) and a pH of 7.3. Recalling the normal bicarbonate (22 to 28 mM) and PCO2 (33 to 45 mmHg) values, which of the additional test results below would be consistent with the man’s pH and breathing pattern?

**Core Concept**
Diabetic ketoacidosis (DKA) is a complication of diabetes mellitus characterized by hyperglycemia, metabolic acidosis, and ketosis. The body fails to utilize glucose for energy, leading to the breakdown of fatty acids to ketones, which accumulate and cause metabolic acidosis.

**Why the Correct Answer is Right**
The patient's presentation of Kussmaul respirations (deep, labored breathing) is a compensatory mechanism to blow off CO2 and decrease the acidity of the blood. The initial venous blood gas shows a pH of 7.3, indicating metabolic acidosis. The expected response would be an increase in ventilation to decrease the PCO2 and increase the pH. Given the normal bicarbonate and PCO2 values, the patient's pH and breathing pattern would be consistent with metabolic acidosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Anion gap would be elevated in DKA due to the accumulation of ketones, which are not measured by routine electrolyte panels.
**Option B:** Metabolic alkalosis would be characterized by a high pH (> 7.4) and low PCO2, which is opposite of the patient's presentation.
**Option C:** Respiratory alkalosis would be characterized by a low PCO2 (< 33 mmHg), which is not consistent with the patient's Kussmaul respirations. **Option D:** Lactic acidosis would have a different clinical presentation and would not be consistent with the patient's high glucose level and Kussmaul respirations. **Clinical Pearl / High-Yield Fact** In DKA, the anion gap is often elevated due to the accumulation of ketones, which can be estimated by the formula: Anion Gap = (Na+ + K+) - (Cl- + HCO3-). This can be a useful tool in diagnosing DKA. **Correct Answer:** A. Elevated anion gap.

✓ Correct Answer: B. A bicarbonate of 15 mM and PCO2 of 30 mmHg