A 60-year-old man is brought to the emergency department by a neighbor who found him lethargic and confused in his apartment. The neighbor notes that the patient has a history of severe alcohol use disorder and has been drinking heavily for the past week. He has also had multiple episodes of non-bilious vomiting over the last three days. Physical examination reveals dry mucous membranes and decreased skin turgor. Laboratory studies are obtained:
| Laboratory Study | Result |
|---|---|
| Serum sodium | |
| Serum potassium | |
| Serum chloride | |
| Serum bicarbonate | |
| Blood urea nitrogen (BUN) | |
| Serum creatinine | |
| Blood glucose |
Arterial blood gas on room air reveals a pH of and PaCO of .
Calculate the patient's delta-delta ratio, defined as the change in anion gap divided by the change in serum bicarbonate (). Assume a normal anion gap of (calculated without potassium) and a normal serum bicarbonate of .
Answer: 3
Answer
3
The patient presents with alcoholic ketoacidosis (AKA) from heavy alcohol use, which generates a high anion gap metabolic acidosis. He also has a concurrent metabolic alkalosis from severe vomiting (loss of gastric HCl). The delta-delta ratio quantifies the relationship between the accumulation of unmeasured anions and the consumption of bicarbonate. An anion gap of 36 mEq/L yields a ΔAG of 24, while the bicarbonate of 16 mEq/L yields a ΔHCO3 of 8. The resulting ratio of 3.0 (which is > 2.0) mathematically confirms the presence of a superimposed metabolic alkalosis, as the rise in unmeasured anions significantly exceeds the drop in bicarbonate.
Step-by-Step Solution
Key Concept
The delta-delta ratio is used in the evaluation of high anion gap metabolic acidosis to identify concurrent mixed metabolic acid-base disorders; a ratio greater than 2.0 indicates a superimposed metabolic alkalosis.