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Detailed information of METABOLIC ACIDOSIS
METABOLIC ACIDOSIS
DEFINITION:
A disorder characterized by an excess of circulating endogenous
and exogenous acids associated with a decreased blood-buffering
capacity (decreased bicarbonate).
EPIDEMIOLOGY:
- incidence: ?
- age of onset:
- risk factors:
PATHOGENESIS:
- metabolic acidosis can occur in the presence or absence of
an anion gap (an anion gap reflects the quantity of unmeasured
anions)
- a normal anion gap hyperchloremic metabolic acidosis is
found in such disorders as Fanconi Syndrome, Renal Tubular
Acidosis, and Congenital Adrenal Hyperplasia
- a wide anion gap metabolic acidosis is found in conditions
where there is an excess of circulating exogenous or endogenous
acids:
- elemental formula
- ethanol/methanol
- iron toxicity
- isoniazid
- paraldehyde
- polyethylene glycol
- salicylate
2. Endogenous Acids (due to Inborn Errors of Metabolism)
- Congenital Lactic Acidoses
2. Secondary
- hypoxia/dehydration
- GSD-Ia - Von Gierke Disease
- Gluconeogenesis Disorders
- Fructose-1,6-Diphosphatase Deficiency
- Pyruvate Carboxylase Deficiency
- Pyruvate Dehydrogenase (Decarboxylase)
- Deficiency
- Organic Acidurias
- Cytochrome C Oxidase Deficiency
2. Fatty Acid*
- Fatty Acid Oxidation Disorders
3. Amino Acid
- Amino Acidurias
- Maple Syrup Urine Disease (MSUD)
4. Organic Acid
5. Keto Acid
- Organic Acidurias
- Methylmalonic Aciduria
- Propionic Aciduria
- Isovaleric Aciduria
6. Ketones#
CLINICAL FEATURES:
- lethargy progressing to coma
- hypotonia
- seizures
- spasticity
2. Other Manifestations
- persistent vomiting (+/- dehydration)
- tachypnea
- hypothermia
INVESTIGATIONS:
- blood gas (to determine a metabolic acidosis)
- electrolytes (to determine anion gap)
- Na - (HCO3 + Cl)
- normal is between 12-15 mEqu/L
- if >15 with a normal Cl, look for an excess of exogenous
or endogenous acids
- glucose (hyperglycemia suggests Diabetes Mellitus)
- ammonia (secondarily elevated)
- lactic acid (+/- pyruvic acid)
- BUN, creatinine
- plasma amino acids
2. Urine
- ketones (ketosis is always an abnormal finding in a
newborn)
- reducing substances (Clinistix [glucose], Clinitest [galactose,
fructose])
- urine organic acids
- urine amino acids
3. CBC
- anemia, leukopenia, and/or thrombocytopenia are associated
with organic acidurias
2. Second Line
- calcium, liver function tests, uric acid, carnitine, very
long chain fatty acids
2. Urine
- DNPH test (for MSUD)
- acetone, sulfites, pH
3. Diagnostic
- on tissue samples (liver), leukocytes, cultured skin
fibroblasts
2. Molecular DNA Studies
MANAGEMENT:
- intubate and ventilate for respiratory distress/arrest
- rehydrate if dehydrated
- treat hypothermia
- treat seizures
- correct hypoglycemia
2. Diet
- NPO
- initially avoid all dietary protein
- provide adequate caloric intake to encourage tissue
anabolism (avoid lactose and sucrose)
3. Correct Acidosis
- rehydrate
- bicarbonate boluses or infusion
- indicated with severe acidosis (pH <7.1; HCO3 <5 mmol/L)
- [Desired HCO3 - Actual HCO3] x body weight (kg) x 0.6 =
calculated HCO3 deficit
- give ½ of calculated HCO3 deficit over 6 hours then
reassess
- exchange transfusion or dialysis
4. Vitamin Cocktail
- vitamins B6 and B12, biotin, cobalamine, carnitine, folic
acid, riboflavin, thiamine
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Pediatric Database - METABOLIC ACIDOSIS
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