Metabolic acidosis can be categorized based on a normal or elevated anion gap (AG) Potentially life-threatening conditions such as septic shock and certain metabolic disorders may present with significant metabolic acidosis Treatment of metabolic acidosis is primarily aimed at the underlying etiology IV sodium bicarbonate may be indicated in the treatment of severe metabolic acidosis Metabolic alkalosis in children most commonly results from diuretic therapy and H+ loss from gastrointestinal secretions Metabolic Acidosis Metabolic acidosis occurs when there is either a net gain of H+ ions or a net loss of bicarbonate (HCO3 − ) ions The two classes of physiologic acids are volatile acids and nonvolatile acids The excretion of volatile acid is achieved by pulmonary ventilation, and the elimination of nonvolatile acid is achieved by renal excretion Clinical manifestations The clinical manifestations of metabolic acidosis are variable and will depend on the underlying etiology and severity Children may be asymptomatic or present with a variety of acute or chronic manifestations such as tachypnea, abdominal pain, vomiting, lethargy, neurologic abnormalities, and failure to thrive Inquiries regarding the presence and duration of symptoms such as diarrhea, polyuria, and poor growth should be included in the historical assessment The physical examination should include an assessment of perfusion and measurement of growth parameters to determine if growth has been impaired Evaluation of metabolic acidosis ideally begins with an assessment of the venous or capillary blood gas, which defines systemic pH, pulmonary compensation, and may identify the presence of complex acid–base disorders (mixed acid–base disorders) Arterial samples are discouraged in children because the information that is gained does not justify the pain of the procedure Venous or capillary samples are sufficient in the ED setting The serum bicarbonate is typically measured indirectly by blood gas or directly by adding a strong acid to venous blood and observing the amount