Metabolic Acidosis is defined as which of the following?

• A. Excess acid from poor perfusion
• B. Regulation of pH
• C. Measure of acidity or alkalinity
• D. Elevated CO2

Answer: (A)

Metabolic acidosis is defined by a primary decrease in bicarbonate (HCO3-) in the blood that drives the arterial pH down, reflecting a net gain of acids or a loss of base from non-respiratory processes. In other words, there is acidemia due to a bicarbonate deficit or acid accumulation, and the body tries to compensate by increasing ventilation to blow off CO2, which helps raise the pH toward normal. Poor tissue perfusion can cause a type of metabolic acidosis (lactic acidosis), but the defining feature remains the low bicarbonate with acidemia, not merely “excess acid from poor perfusion.” By contrast, regulation of pH is the body’s control mechanism, measuring acidity or alkalinity is simply a pH value, and elevated CO2 points to respiratory acidosis, not metabolic.