A venous blood gas shows pH 7.52, Cl- 90 mmol/L, K+ 3.1 mmol/L, pCO2 48 mmHg, and pCO3 34 mmol/L. What is the presumptive diagnosis?

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Multiple Choice

A venous blood gas shows pH 7.52, Cl- 90 mmol/L, K+ 3.1 mmol/L, pCO2 48 mmHg, and pCO3 34 mmol/L. What is the presumptive diagnosis?

Interpreting this venous blood gas starts with noticing the pH is alkaline, which means the blood is alkalemic. The markedly high bicarbonate level (34 mmol/L) indicates a metabolic rather than a respiratory primary disturbance. The pCO2 is 48 mmHg, which is elevated, showing the lungs are hypoventilating to retain CO2 as a compensatory response to the metabolic alkalosis. The combination of high bicarbonate with an alkaline pH and a raised pCO2 fits metabolic alkalosis with respiratory compensation. The low chloride and low potassium support a renal/volume-depletion–type metabolic alkalosis, commonly seen with diuretic use or vomiting. In short, this pattern aligns with metabolic alkalosis driven by renal mechanisms, with the lungs compensating by increasing CO2 retention. Other patterns would not match: a primary respiratory alkalosis would have a low pCO2, and a metabolic acidosis would show a low bicarbonate and an acidic pH, while a true mixed disorder would not yield a straightforward alkalemia with this compensatory pattern.

Interpreting this venous blood gas starts with noticing the pH is alkaline, which means the blood is alkalemic. The markedly high bicarbonate level (34 mmol/L) indicates a metabolic rather than a respiratory primary disturbance. The pCO2 is 48 mmHg, which is elevated, showing the lungs are hypoventilating to retain CO2 as a compensatory response to the metabolic alkalosis. The combination of high bicarbonate with an alkaline pH and a raised pCO2 fits metabolic alkalosis with respiratory compensation. The low chloride and low potassium support a renal/volume-depletion–type metabolic alkalosis, commonly seen with diuretic use or vomiting. In short, this pattern aligns with metabolic alkalosis driven by renal mechanisms, with the lungs compensating by increasing CO2 retention. Other patterns would not match: a primary respiratory alkalosis would have a low pCO2, and a metabolic acidosis would show a low bicarbonate and an acidic pH, while a true mixed disorder would not yield a straightforward alkalemia with this compensatory pattern.

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