In uncompensated metabolic acidosis, which value remains normal?

In uncompensated metabolic acidosis, the value that remains normal is the PCO2 (partial pressure of carbon dioxide). In this condition, the primary disturbance is a decrease in plasma bicarbonate due to increased acid production or decreased acid excretion by the kidneys. This leads to a lower pH, indicating acidosis.

In a state of uncompensated metabolic acidosis, the body has not yet activated compensatory mechanisms such as respiratory compensation, which would involve hyperventilation to blow off CO2 and raise pH. Therefore, the PCO2 levels will typically remain within their normal range, as the respiratory system hasn't adjusted yet to correct the metabolic disturbance.

On the other hand, plasma bicarbonate would be decreased, reflecting the acidosis. p50 refers to the partial pressure of oxygen at which hemoglobin is 50% saturated and is generally not directly affected by acid-base disturbances. Total CO2, which includes bicarbonate and dissolved CO2, also decreases as bicarbonate concentration falls. Thus, in uncompensated metabolic acidosis, PCO2 remains the value that does not change from its normal range initially.