Hypoglycemia in the newborn, define as the plasma glucose concentration low enough to cause signs and symptoms of altered brain function.
Plasma glucose (PG) concentrations
– In terms: <40mg/dL (<2.2 mmol/L)
– In pre-terms <30mg/dL (<1.7 mmol/L)
Consider this the first 24 hours of life and <45 mg/dl thereafter.
According to the American Academy of Breastfeeding Medicine
A “reasonable (although arbitrary) goal” is to maintain plasma glucose concentrations between 40 and 50 mg/dL (between 2.2and 2.8 mmol/L)
“Acceptable and stable” value of >40 mg/dL (>2.2 mmol/L)
Glucose in the healthy newborn
In every newborn, blood glucose concentration drops for a short period of time (between 1 to 2 hours after birth) AKA transitional neonatal hypoglycemia (TNH).
- Between the first 2-3 hours of life drops 25-35mg/dL
- ~3hrs of life goes as low as one can get, stabilizing at 3 to 4 hours
- In 24-48hrs keeps increasing to reach normal levels
Note: This is why diagnostic evaluation for persistent hypoglycemia must be delay until 2 to 3 days after birth.
Newborns at risk
- Small for gestational age or Intrauterine growth retardation (IUGR)
- Preterm infants
- Large for gestational age
- Post-term infants
- Infant of diabetic mother
- Healthy babies who were hypoxic during labor or depressed at birth
Note: the amount of glycogen stored has been altered in all these neonates
May be asymptomatic at first
– Jitteriness / tremors (shaking)
– Cyanosis (skin turns blue or purplish in color)
– Apnea / Irregular respirations
– Weak cry / Irritability (high-pitched cry)
– Lethargy / deep unresponsiveness and inactivity
– Limpness /flaccid
– Refusal to feed
– Inability to regulate body temperature (hypothermia)
Recollecting blood sample – Heel-stick procedure
Is good to warm heel prior sample to increase blood flow in heel.
Recommended site for sampling in neonates:
Lateral plantar surface beyond an imaginary line drawn medially from the middle of the great toe to the heel and posteriorly from between the 4th and 5th toes to the heel.
Why this sample is taken laterally?
The neonates with high risk for hypoglycemia usually are small, sometimes multiple samples must be taken which can lead to tissue injury and inflammation, making the heel more tender and hypersensitive. There is more room in the heels laterally and no damage to the calcaneus. This was studied by ultrasound measuring the distance between the skin surface and the perichondrium of the calcaneus, it was calculated to be 2.38 mm
Note: safely heel-stick used depth ~ 2.4 mm on any part of the plantar surface except the posterior aspect of the heel
Complications of heel-stick procedure
Rare but can develop cellulitis, perichondritis, calcaneal osteomyelitis or abscesses.