Which arterial blood gas pattern indicates metabolic acidosis with an elevated anion gap?

Which arterial blood gas pattern indicates metabolic acidosis with an elevated anion gap?

• A. High pH, high HCO3-, PaCO2 may be high or normal depending on compensation.
• B. Low pH, low HCO3-, low or normal PaCO2 with an elevated anion gap.
• C. Low pH, high HCO3-, PaCO2 elevated.
• D. High pH, low HCO3-, PaCO2 low

Answer: (B)

In ABG interpretation, metabolic acidosis shows acidemia with a decrease in bicarbonate, and the body tries to compensate by blowing off CO2, so the PaCO2 falls or remains in the low/normal range. When the anion gap is elevated, there are extra unmeasured anions (like lactate, ketoacids, or toxins) contributing to the acidosis. The pattern that matches this scenario is low pH, low bicarbonate, and a PaCO2 that is low or inappropriately normal due to respiratory compensation. The added clue of an elevated anion gap points to a high anion gap metabolic acidosis rather than a normal gap one.

In ABG interpretation, metabolic acidosis shows acidemia with a decrease in bicarbonate, and the body tries to compensate by blowing off CO2, so the PaCO2 falls or remains in the low/normal range. When the anion gap is elevated, there are extra unmeasured anions (like lactate, ketoacids, or toxins) contributing to the acidosis.

The pattern that matches this scenario is low pH, low bicarbonate, and a PaCO2 that is low or inappropriately normal due to respiratory compensation. The added clue of an elevated anion gap points to a high anion gap metabolic acidosis rather than a normal gap one.