Correction of severe metabolic acidosis: a physiological approach.

1 - Five patients with severe metabolic acidosis secondary to methanol poisoning were studied before and after receiving 6.7 to 10 mEq NaHCO3/kg body weight. 2 - Two thirds of the infused HCO3- left the extracellular space and, since its apparent volume of distribution was much larger than under normal conditions, it largely overestimated HCO3- needs. On the contrary, the volume of distribution of the buffer base excess was found to be more stable and little affected by the acid-base status. 3 - Based on these observations, a simple method for estimating HCO3- needs in severe metabolic acidosis is proposed, requiring only the initial excess buffer base space which is calculated from body weight and blood buffer base excess values obtained before and after a first dose of bicarbonate.