A 22-year-old man with type 1 diabetes mellitus presents to the emergency department with abdominal pain, nausea, and persistent vomiting for the past 2 days. He reports missing his last several doses of insulin. His vital signs include a heart rate of 118/min and a blood pressure of 90/60 mm Hg. Laboratory studies show the following:
| Laboratory Test | Result |
|---|---|
| Sodium () | 142 mEq/L |
| Potassium () | 4.5 mEq/L |
| Chloride () | 92 mEq/L |
| Bicarbonate () | 14 mEq/L |
| Blood urea nitrogen | 35 mg/dL |
| Creatinine | 1.4 mg/dL |
| Glucose | 450 mg/dL |
Assuming a normal reference serum anion gap of 12 mEq/L and a normal serum bicarbonate of 24 mEq/L, what is the patient's delta ratio (calculated as the change in anion gap divided by the change in serum bicarbonate)? (Provide the exact calculated decimal value).
Answer: 2.4
Answer
2.4
The delta ratio is used to determine if a mixed acid-base disorder is present in the setting of a high anion gap metabolic acidosis. First, the patient's anion gap is calculated as mEq/L. The change in the anion gap () is the calculated gap minus the normal gap: mEq/L. The change in bicarbonate () is the normal bicarbonate minus the patient's bicarbonate: mEq/L. The delta ratio is . A ratio greater than 2.0 indicates that the bicarbonate level is higher than would be expected from the buffering of the excess acid alone, implying a concurrent primary metabolic alkalosis (in this case, secondary to the patient's persistent vomiting).
Step-by-Step Solution
Key Concept
Calculation and interpretation of the delta ratio in mixed acid-base disorders