Metabolic acidosis is present whenever the arterial pH is less than 7.35 and PaCO 2 is less than 35 mm Hg. In acute respiratory acidosis, bicarbonate initially rises because of the reaction of carbon dioxide with water and the formation of H2CO3. By definition, a patient cannot have a state of metabolic acidosis and a state of metabolic alkalosis at the same time. If pH and PaCO 2 are both above normal, bicarbonate must also be above normal. One reason the measured serum bicarbonate may not agree with the value calculated from the pH and the PaCO 2 is the variation of the bicarbonate buffer system's pK value.
Diarrhea leads to metabolic alkalosis through the loss of gastrointestinal hydrogen ions.
The compensation for chronic respiratory acidosis is renal excretion of bicarbonate. Exeunt Omnes, The Smart Set, p. 139, Dec. 1919. The ventilatory response to acute base deficit in humans, Ann. See also General References in Appendix G. Respiratory disorders Arbus, G.S., Hebert, L.A., Levesque, P.R., et al. Characterization and clinical application of the ''significance band'' for acute respiratory alkalosis, N. Engl.