Flashcards in Glucose Metabolism Deck (70)
What is the primary fuel of the brain?
glucose; unlike the liver, skeletal muscle or cardiac muscle, the brain cannot store adequate amounts of glucose in the form of glycogen. it requires a steady supply of glucose to function normally.
How is glucose provided to the fetus?
fetal glucose is supplied along a concentration gradient by a carrier mediated transport system across the placenta--> it readily crosses the placenta
When do fetal stores of glucose first appear?
present by 9th wk GA
When is the majority of glucose stored but the fetus?
in the 3rd trimester, particularly in the last month
At term, how do the glucose stores of an infant compare to that of an adult?
infant stores are 3x > and adult
In preparation for delivery, what changes occur with glucose storage?
glucagon levels increase and insulin levels decrease
What is the definition of hypoglycemia?
the def and mgmt of hypoglycemia remains controversial an recommendations vary; measurement of serum glucose is the amount dissolved glucose in the blood stream
What is the most common metabolic problem in the newborn?
Why can't hypoglycemia can't be described by a single value?
bc it may be different bw babies due to their physiologic immaturity and their current pathophysiology
When do glucose levels reach their nadir?
30-90 min of age
What can be indicated by the presentation of asymptomatic hypoglycemia in the neonate?
other energy substrates such as lactate and ketone bodies are providing the adequate fuel for the brain
What happens to samples of blood left out at room temperature?
for every hour it is left out, it decreases the value by 13-18g/dL
Point of care testing utilizes what sample of blood?
whole blood; if you send a sample to the lab, it should be just a little higher than the value you get at the bedside
How do whole blood measurements of glucose compare to plasma values?
whole blood measurements are approximately 15% lower than plasma values
How do venous blood measurements of glucose compare to arterial values?
venous samples are approximately 10-15% lower than plasma values
What sample of blood is considered the "true level"?
What other factors can alter a glucose level?
elevated HCT will alter results
What stimulates the processes of glycogenolysis and gluconeogensis?
epinephrine, norepinephrine, growth hormone, cortisol and glucagon
What is the definition of glycogenolysis?
the initial process to convert glycogen into glucose
What is the definition of gluconeogenesis?
the initial glucose production method-break down CHO sources and convert them into glucose; not effective or efficient
What are prenatal and family history related risk factors for the postnatal development of hypoglycemia?
MOB c glucose alt; previous LGA babies, LGA, h/o previous stillbirths, HTN/PIH, h/o metabolic dz
What are birth history related risk factors for the postnatal development of hypoglycemia?
low APGARs, poor fetal tracing, signs of infix (PROM, maternal fever)
What are physical exam findings that increase the risk for the postnatal development of hypoglycemia?
SGA, LGA, IUGR, Beckwith-Wiedmann
What is universal screening for hypoglycemia?
screen every baby for hypoglycemia, AAP now suggests only screening the babies at high risk
What is included in the Beckwith-Wiedmann constellation?
known for profound and/or persistent hypoglycemia, physically typically LGA, protuberant tongue and abnormal umbilicus (may have an omphalocele)
What are the common causes of neonatal hypoglycemia?
1) inadequate substrate supply
2) abnormal endocrine fx
3) increased glucose utilization
4) iatrogenic causes
What percentage of hypoglycemia is r/t inadequate substrate supply?
What infants are at the greatest risk for hypoglycemia secondary to inadequate substrate supply?
VLBW infant (<1250g), SGA, discordant twins
What are the mechanisms of inadequate substrate supply r/t hypoglycemia r/t pulmonary and neuro?
1) if they have a significant respiratory course, we know that hypoxia uses glucose as an energy source, depleting what glucose stores were present 2) babies with decreased glucose stores may also have high glucose brain utilization