Anion Gap: 21 mmol/L; URIC: 35 μmol/L; pCO2: 20; pHCO3: 14. What is the likely diagnosis?

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Multiple Choice

Anion Gap: 21 mmol/L; URIC: 35 μmol/L; pCO2: 20; pHCO3: 14. What is the likely diagnosis?

This combination reflects a mixed acid–base disturbance typical of salicylate poisoning. The high anion gap (21) plus a low bicarbonate (14) shows metabolic acidosis with an increased gap from accumulated organic acids. At the same time, the very low pCO2 (20) indicates a primary respiratory alkalosis component due to stimulation of the medullary respiratory center by salicylates. If you apply Winter’s formula for metabolic acidosis (expected pCO2 ≈ 1.5 × HCO3− + 8, about 29 mmHg here), the measured pCO2 of 20 is lower than expected, confirming a concurrent respiratory alkalosis. Low serum uric acid (35 μmol/L) supports salicylate poisoning because salicylates promote uric acid excretion, lowering its level in the blood. Other possibilities don’t fit as well: diabetic ketoacidosis typically centers on ketones and hyperglycemia without this striking mixed alkalosis picture; methanol poisoning doesn’t explain the uric acid drop; dehydration alone would not produce a high anion gap metabolic acidosis with a concurrent respiratory alkalosis.

This combination reflects a mixed acid–base disturbance typical of salicylate poisoning. The high anion gap (21) plus a low bicarbonate (14) shows metabolic acidosis with an increased gap from accumulated organic acids. At the same time, the very low pCO2 (20) indicates a primary respiratory alkalosis component due to stimulation of the medullary respiratory center by salicylates. If you apply Winter’s formula for metabolic acidosis (expected pCO2 ≈ 1.5 × HCO3− + 8, about 29 mmHg here), the measured pCO2 of 20 is lower than expected, confirming a concurrent respiratory alkalosis.

Low serum uric acid (35 μmol/L) supports salicylate poisoning because salicylates promote uric acid excretion, lowering its level in the blood.

Other possibilities don’t fit as well: diabetic ketoacidosis typically centers on ketones and hyperglycemia without this striking mixed alkalosis picture; methanol poisoning doesn’t explain the uric acid drop; dehydration alone would not produce a high anion gap metabolic acidosis with a concurrent respiratory alkalosis.

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