Hypoglycemia in the Newborn

Question 1

Why are newborn brains so prone to the effects of hypoglycemia?

Answer 1

1: They are growing a lot during this time

Question 2

Fetal glycogen storage

Answer 2

Much of fetal glycogen storage occurs during the last 30% of gestation, and is promoted by a high insulin:glucagon ratio as well as high cortisol.

If the infant experiences hypoglycemia or hypoxemia during this period, glycogen phosphorylase will be activated to defend the fetal energy supply, however this means that after birth the infant will have less glycogen stored to maintain its blood sugar.

This also means that premature infants have less stored glycogen and are thus at greater risk for hypoglycemia.

Question 3

The average healthy infant has a ___ supply of glycogen at birth

Answer 3

The average healthy infant has a 10 hour supply of glycogen at birth

Consequentially, babies need to start feeding soon after birth.

Question 4

Paradoxically, both ___ infants and ___ infants are at risk for hypoglycemia

Answer 4

Paradoxically, both IUGR infants and LGA infants are at risk for hypoglycemia

Question 5

Etiologies of transient neonatal hypoglycemia

Answer 5

• Prematurity
• IUGR
• Asphyxia
• Hypothermia
• Sepsis
• Maternal diabetes (CDM or GDM)
• Erythroblastosis fetalis
• Exposure to beta-agonist tocolytics

Question 6

Etiologies of neonatal hypoglycemia with prolonged periods of hypoglycemia

Answer 6

Familial hyperinsulinism

Inborn errors of metabolism (glycogen storage diseases)

Question 7

Most common cause of hyperinsulinism of the newborn

Answer 7

Maternal diabetes

Question 8

Mechanism of hyperinsulinism in erythroblastosis fetalis

Answer 8

Infants with erythroblastosis fetalis have an increased number of pancreatic beta cells, which thereby causes hyperinsulinism.

The reason for this is not fully understood.

Question 9

Familial recessive hyperinsulinism

Answer 9

• Defect in the K+-ATP channel in beta cells
• Causes congenital, persistent hyperinsulinism

Question 10

___ should be strongly suspected in the term infant who has hypoglycemia without apparent risk factors.

Answer 10

Sepsis should be strongly suspected in the term infant who has hypoglycemia without apparent risk factors.

Question 11

Confirming a diagnosis of hyperinsulinemia in the newborn

Answer 11

• Two ways:
  
  1. Demonstrate elevated insulin when the infant is hypoglycemic with symptoms
  2. Demonstrate elevation in IGFBP-1 (insulin-like growth factor binding protein-1)

Question 12

Management of asymptomatic hypoglycemia

Answer 12

In infants with hypoglycemia who display no symptoms, enteral feeding with formula may be attempted first.

Formula is better than dextrose in water as its protein and fat will create a sustained elevation in blood sugar, while dextrose will provide only a temporary boost.

Even if concentrations normalize, continue monitoring preprandial and postprandial glucose levels.

Question 13

Management of symptomatic hypoglycemia

Answer 13

Infants with hypoglycemia who are symptomatic should jump straight to IV dextrose therapy.

This should be given as a mini-bolus followed by a dextrose drip. The mini-bolus is to avoid excessive insulin secretion and rebound hypoglycemia.

While receiving drip therapy, they should also continue breastfeeding.

If refractory, adjunct pharmacologic therapies may be employed.

Question 14

Adjunct pharmacologic therapies for refractory neonatal hypoglycemia

Answer 14

• Hydrocortisone or Prednisone: Decrease peripheral glucose utilization
• Glucagon: Stimulates glycogenolysis
• Diazoxide: Inhibits insulin secretion
• Octreotide acetate (somatostatin acetate): Inhibits insulin and GH release

Question 15

If refractory to pharmacologic therapy or thought to be due to primary pancreas pathology, ___ is the most premanent intervention for neonatal hypoglycemia

Answer 15

If refractory to pharmacologic therapy or thought to be due to primary pancreas pathology, subtotal pancreatectomy is the most premanent intervention for neonatal hypoglycemia

Question 16

Hypoglycemia brain injury

Answer 16

Even as blood sugar varies, CSF sugar remains fairly constant as it is regulated by glucose transporters at the choroid plexus, not just simple diffusion. Infants with moderate hypoglycemia are therefore more at risk of intraventricular hemorrhage due to changes in bloodflow secondary to hypoglycemia rather than neuroglycopenia.

If blood sugar is very low and does result in neuroglycopenia, glutamate builds up in the synaptic clefts and binds to NDMA-receptors (predominant glutamate receptors in the neonatal brain), resulting in excitotoxicity that manifests as seizure and areas of brain necrosis.