Pediatric emergency medicine trisk 2432 2432

Ketones (Ketostix,
Acetest)

Myoglobin

Absence of reducing substances does not eliminate
possibility of IEM
Elevated ketones
Ketones detected by Ketostix, Chemstix, Acetest
Aminoacidopathies
Inappropriate ketones
Organic acidemias
Ketonuria in neonates
Carbohydrate
Ketonuria, normal glucose beyond neonate
intolerance disorders Low/absent ketones, hypoglycemia beyond neonate
Carbohydrate
production/utilization
disorders
Mitochondrial disorders
Absent ketones,
hypoketosis
Fatty acid oxidation
defects
Myoglobin present
Not always present, even with rhabdomyolysis,
especially if creatinine kinase <10,000 IU
Organic acidemias
Carbohydrate
production/utilization
disorders

Mitochondrial disorders

a Within

disease categories, not all diseases have the laboratory abnormality. In disorders of protein metabolism, carbohydrate metabolism
and fatty acid oxidation defects and abnormality may be present only during acute crisis.
IEM, inborn error of metabolism.
Adapted from Weiner DL. Inborn errors of metabolism. In: Aghababian RV, ed. Emergency Medicine: The Core Curriculum . Philadelphia,
PA: Lippincott-Raven; 1999:705.

Hypoglycemia. Serum glucose level of less than 40 mg/dL in the neonate and less than 50 mg/dL
beyond the neonatal period should be considered abnormally low. Even with poor oral intake and/or
metabolic stressors, hypoglycemia less than 45 mg/dL is unusual in the normal child. Hypoglycemia may
cause a decreased level of consciousness, irritability, and seizures. Newborns may also have a highpitched cry, hypothermia, cyanosis, and poor feeding. In the older child or adult, symptoms may include
headache, blurred vision, repeated yawning, diaphoresis, pallor, and nervousness. Hypoglycemia most
commonly occurs with fatty acid oxidation defects, disorders of carbohydrate metabolism, and
hyperinsulinemic states. Low serum glucose can also be seen with aminoacidopathies and organic
acidemias due to inhibition of hepatic gluconeogenesis in these disorders. In patients with hypoglycemia,
absence of ketonuria is highly suggestive of a fatty acid oxidation defect. On the other hand, neonates
should never have ketonuria, and when present, it is suggestive of an IEM. Beyond the neonatal period,
hypoglycemia with inappropriately low or absent ketones is also always abnormal. The presence of
urinary ketones in a patient with hypoglycemia does not rule out an IEM, particularly short-chain fatty
acid oxidation defects, organic acidemias, disorders of carbohydrate metabolism, or ketotic hypoglycemia
of childhood. Hypoketosis, if not evident from the urine, can be determined by measuring ketones (3hydroxybutyrate and acetoacetate) and free fatty acids in blood. In patients with hypoglycemia, the
following laboratory studies should be sent: plasma amino acids, acylcarnitine, urine organic acids and
acylglycines, serum cortisol, insulin, liver function tests (LFTs), and ammonia. Growth hormone is not an
informative test in the acute setting. Causes of hypoglycemia other than IEM include liver disease;
hyperinsulinemia; toxic ingestions of salicylates, β-blockers, ethanol, or polyethylene glycol; maternal
diabetes/gestational diabetes; prematurity or small for gestational age; asphyxia; and sepsis.