What is metabolic acidosis?

Updated: Dec 09, 2020
  • Author: Bret A Nicks, MD, MHA; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Classically, metabolic acidosis is defined as a state of decreased systemic pH resulting from either a primary increase in hydrogen ion (H+) or a reduction in bicarbonate (HCO3-) concentrations. In the acute state, respiratory compensation of acidosis occurs by hyperventilation resulting in a relative reduction in the partial pressure of carbon dioxide (PaCO2). Chronically, renal compensation occurs by means of reabsorption of HCO3. [1, 2, 3]

Acidosis arises from an increased production of acids, a loss of alkali, or a decreased renal excretion of acids. The underlying etiology of metabolic acidosis is classically categorized into those causes that result in an elevated anion gap (AG) (see the Anion Gap calculator) and those that do not. Lactic acidosis (LA), identified by an accumulation of plasma lactate concentration, is one type of anion gap metabolic acidosis and may manifest from numerous conditions. [2, 4, 5]  Clinical context and severity govern the effect of lactic acidosis, with mortality increasing by a factor of about three when the condition is associated with sepsis or low-flow states. Lactic acidosis remains the most common cause of metabolic acidosis in hospitalized patients.

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