A venous blood gas shows Anion Gap 20 mmol/L, Cl- 112 mmol/L, K+ 5.3 mmol/L, pH 7.18, HCO3- 14 mmol/L, pCO2 28 mmHg. The presumptive diagnosis is:

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Multiple Choice

A venous blood gas shows Anion Gap 20 mmol/L, Cl- 112 mmol/L, K+ 5.3 mmol/L, pH 7.18, HCO3- 14 mmol/L, pCO2 28 mmHg. The presumptive diagnosis is:

This question tests how to identify a metabolic acid–base disturbance and recognize appropriate respiratory compensation. The blood gas shows acidemia (pH 7.18) with low bicarbonate (HCO3− 14 mmol/L), which points to a metabolic acidosis. The anion gap is elevated (20 mmol/L), indicating a high anion gap metabolic acidosis, meaning unmeasured acids are accumulating. To see if the respiratory system is compensating, use Winter’s formula: predicted pCO2 ≈ 1.5 × [HCO3−] + 8 ± 2. With [HCO3−] = 14, predicted pCO2 ≈ 29 ± 2 mmHg. The observed pCO2 is 28 mmHg, which falls within that range, showing appropriate respiratory (lung) compensation. Therefore, the presumptive diagnosis is metabolic acidosis with respiratory compensation. The data do not support a primary respiratory acidosis or metabolic alkalosis, and the compensation is present rather than absent.

This question tests how to identify a metabolic acid–base disturbance and recognize appropriate respiratory compensation. The blood gas shows acidemia (pH 7.18) with low bicarbonate (HCO3− 14 mmol/L), which points to a metabolic acidosis. The anion gap is elevated (20 mmol/L), indicating a high anion gap metabolic acidosis, meaning unmeasured acids are accumulating. To see if the respiratory system is compensating, use Winter’s formula: predicted pCO2 ≈ 1.5 × [HCO3−] + 8 ± 2. With [HCO3−] = 14, predicted pCO2 ≈ 29 ± 2 mmHg. The observed pCO2 is 28 mmHg, which falls within that range, showing appropriate respiratory (lung) compensation. Therefore, the presumptive diagnosis is metabolic acidosis with respiratory compensation. The data do not support a primary respiratory acidosis or metabolic alkalosis, and the compensation is present rather than absent.

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