A patient with diarrhoea has pH 7.25, HCO3 of 12 mmol/L and PaCO2 of 28 mmHg. By Winter's formula (1.5 x HCO3 + 8, plus or minus 2), what is the interpretation?
Answer and explanation
Correct answer: B. Metabolic acidosis with appropriate respiratory compensation
- Step 1: A low pH with low bicarbonate indicates metabolic acidosis. Step 2. Winter's formula gives an expected PaCO2 of 1.5 x 12 + 8 = 26 (range 24 to 28), and 28 is within it. Answer: appropriate compensation. Why not the others: A value in the expected range excludes a second respiratory disorder; a low HCO3 excludes a primary respiratory acidosis.
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