Pediatric emergency medicine trisk 2877 2877
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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
