Pediatric emergency medicine trisk 2880 2880
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Management. The management of metabolic acidosis should focus on the
identification and treatment of the underlying cause and ensuring adequate
perfusion. The immediate therapy of metabolic acidosis in the ED generally
depends on the severity of the disorder. In children with severe acidemia
(serum pH less than 7.10), bicarbonate therapy is generally indicated. The
basis for correcting severe acidosis is the negative impact severe acidemia
has on cardiac function, including impaired cardiac contractility and
increased risk for cardiac arrhythmias. Exceptions would include metabolic
acidosis in patients with DKA, as lower thresholds for pH are allowed
before bicarbonate is provided given the expected metabolism of ketoacid
into bicarbonate with insulin and fluid repletion (see Chapter 89 Endocrine
Emergencies ). The role of alkali therapy remains controversial in
hypoperfusion lactic acidosis and is yet to be resolved. The aim of treatment
in hypoperfusion lactic acidosis is to restore intravascular volume and
perfusion in a timely fashion, which will allow metabolism of lactate anions
to bicarbonate. The potential complications of alkali therapy in metabolic
acidosis include hypercarbia, hypernatremia, transcellular shift of potassium
ion into the intracellular space resulting in hypokalemia, and alkalosis.
Furthermore, alkalosis or an increase in blood pH may precipitate tetany by
promoting binding of calcium to albumin, which reduces the ionized
calcium concentration.
When bicarbonate therapy is to be given, estimating the necessary dose
may prove to be challenging. Given the difficulty in accurately estimating
the bicarbonate deficit, bicarbonate can be given at an initial dose of 0.5 to
1 mEq/kg if clinically indicated with the aim of increasing the systemic pH
to more than 7.20. Further alkali therapy will depend upon the response and
subsequent disease course. If the patient is asymptomatic, the underlying
process can be controlled (e.g., diarrheal dehydration), and tissue perfusion
can be assured, alkali therapy may not be required. In the setting of
asymptomatic chronic metabolic acidosis, such as RTA and CKD,
consultation with an appropriate specialist would be reasonable to guide
oral therapy and avoid complications such as electrolyte derangements and
volume excess.
Metabolic Alkalosis
