Problem. An infant has a "low blood glucose level" on Dextrostix or Chemstrip-bG testing. The exact definition of neonatal hypoglycemia is not agreed on. If symptomatic, no matter what the level, the infant should be treated. It is not possible to define a single blood glucose level that requires intervention in every newborn. Older definitions used glucose < 30mg/dL in the first 24 h of life and <45mg/dL after 24 h in a newborn (controversial). Later, hypoglycemia was defined as a serum glucose <40–45mg/dL in a term or premature infant (controversial). Today many institutions have defined it as a serum glucose <45–50 mg/dL (some use <60 mg/dL) in the first 24 h and <50–60 mg/dL thereafter. It is best to follow your institution's guidelines. In infants with documented hyperinsulinemic states, a value of <60 mg/dL is considered hypoglycemic (controversial).
Has the value been repeated, and has a plasma blood sugar sample been sent to the laboratory? Dextrostix or Chemstrip-bG strips can give incorrect values if the test is not done properly or if the strips used are too old. There can be a wide variation when these results are compared with laboratory-determined plasma levels. Glucose oxidase strips are also quite inaccurate in the low range (<40–50 mg/dL). Note: The glucose concentration in whole blood is 10–15% lower than in the plasma. Never diagnose or treat hypoglycemia based on these screening strips alone. Always send a serum sample to the laboratory before starting treatment.
Is the infant symptomatic? Symptoms of hypoglycemia include apnea, hypotonia, inadequate sucking reflex, irritability, irregular respirations, poor sucking or feeding, exaggerated Moro reflex, cyanosis, tremors, pallor, eye rolling, seizures, lethargy, changes in levels of consciousness, temperature instability, and coma. Some infants can have documented hypoglycemia but no symptoms. Rarely, bradycardia, tachycardia, abnormal cry (high pitched), tachypnea, and vomiting present as manifestations of hypoglycemia.
Is the mother a diabetic? Approximately 40% of infants of diabetic mothers have hypoglycemia. Throughout pregnancy, diabetic mothers have fluctuating hyperglycemia, resulting in fetal hyperglycemia. This fetal hyperglycemia induces pancreatic beta cell hyperplasia, which in turn results in hyperinsulinism. After delivery, hyperinsulinism persists and hypoglycemia results.
How much glucose is the infant receiving? The normal initial glucose requirement is 5–7 mg/kg/min. If the glucose order was written arbitrarily and not calculated on the basis of body weight, the infant may not be getting enough glucose. (For glucose calculations, see Chapter 8.)
Causes of transient hypoglycemia
Sepsis, especially Gram negative.
Asphyxia or hypoxic-ischemic encephalopathy.
Infant of a gestational or insulin-dependent diabetic mother.
Insufficient glucose administration (see Section II, D).
Maternal drugs such as terbutaline, ritodrine, chlorothiazide, chlorpropamide, labetalol, or propranolol.
Large for gestational age (LGA) infants.
Decreased glycogen stores
Intrauterine growth restriction (IUGR) or small for gestational age.
Caloric intake is insufficient.
Causes of recurrent or persistent hypoglycemia
Hormone excess hyperinsulinism
Beckwith-Wiedemann syndrome (visceromegaly, macroglossia, and hypoglycemia).
Islet cell adenoma.
Beta cell hyperplasia or dysplasia.
Growth hormone deficiency.
Corticotropin (adrenocorticotropic hormone) unresponsiveness.
Cortisol deficiency, either from hemorrhage or adrenogenital syndrome.
Pituitary disorders (hypoplasia or aplasia of the anterior pituitary).
Congenital optic nerve hypoplasia.
Hypothalamic hormone deficiencies.
Midline central ...
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