Which ABG pattern is expected in metabolic alkalosis?

Which ABG pattern is expected in metabolic alkalosis?

• A. High pH and low HCO3
• B. Low pH and low HCO3
• C. Low pH and high HCO3
• D. High pH and high HCO3

Answer: (D)

Metabolic alkalosis occurs when there is an excess of base or a loss of hydrogen ions, often with chloride depletion. This drives the arterial pH up, so the blood becomes more alkaline. The body then tries to compensate by hypoventilating to retain CO2, which raises the PaCO2. Therefore the ABG shows an elevated pH with elevated bicarbonate (HCO3−), with a compensatory increase in PaCO2. This pattern—high pH and high HCO3−—is the hallmark of metabolic alkalosis.