Physiology Of The Newborn

Front 1

how does the fetus maintain a blood glucose and what percent does it maintain?

Back 1

By facilitated diffusion across the placenta and 70-80%.

Hint 1

glycogen builds up in the liver, skeleton and cardiac muscles during the later stages of fetal development but with little glucogenesis. the neonate depends on glycolysis until EXOGENOUS glucose is supplied.
Hepatic glycogen stores within 2-3 hours after delivery. this happens more rapidly in premature and SGA babies. The newborn is severely limited in the ability to use fat and protein as substrates to synthesize glucose.

Front 2

what are the clinical signs of hypoglycemia?

Back 2

non specific. weak or high pitched cry, cyanosis, apena, jitteriness, seizures, abnormal eye movements, unstable temperature, hypotonia, weak suck or no signs

Front 3

define neonatal hypoglycemia

Back 3

glucose level less than 40mg/dl.

Hint 3

after 72 hours of age, blood glucose should be 40 or more. surgical newborns are at risk for low blood glucose and a 10% glucose infusion is usually started on admission and blood levels determined. if blood glucose is less tha 40 neging an hourly bolus infusion of 2 ml/kg (4-8 mg/kg/min) of 10% glucose.
rarely hydrocortisone, glucogan, somatostatin is used to treat persistent hypoglycemia.

Front 4

hyperglycemia risk factors

Back 4

common with tpn in very immature infants, less than 30 weeks gestation and less than 1.1 kg birth weight. sepsis

Hint 4

cause is inadeqate insulin response, hyperglycemia may cause IVH
incremental increases in glucose over several days
iv insulin 0.001 to 0.01 U/kg/min

Front 5

Calcium

Back 5

continuously delivered to the fetus by active transport across the placenta
75% of total Ca transported after 28 weeks gestation explains why there is a high incidence of hypocalcemia in extremely preterm infants
newborn nadir levels reached at 24-48 hours after delivery when parathyroid hormone responses become effective.

limited calcium stores, renal immaturity, relative hypoparathyroidism due to renal suppression by high fetal calcium levels.

Hint 5

preterm infants, newborn surgical patients are at greatest risk

hypocalcemia is ionized calcium les than 1 mg/dl.

calcitonin which inhibits Ca mobilization is increased in premature infants

blood transfusion can form Ca Citrate compelxes reducing ionized serum calcium to dangerous levels.

signs of low calcium - cyanosis, myocardial depression, INCREASED muscle tone which helps differentiate from hypoglycemia

treat with 10 calcium gluconate, IV, 1-2 ml/kg over 10 minutes

asymptomatic best treated with calcium gluconate in a does of 50 mg of elemental calcium/kg/day added to maintenance fluid

1 ml of 10% Ca gluconate = 9 mg elemental Ca

Front 6

Magnesium
actively transported placenta
half of total body Mg in plasma and half in soft tissue

Back 6

hypo - maternal diabetes, exchange transfusion, growth retardation, hypoarathyroidism

Hint 6

mag and ca metabolism interrelated
same risk pattern
emergency RX 25-50 mg/kg IV every 6 hours

Front 7

Blood volume
total RBC volume highest at delivery

Estimates of BV - ml/kg
premature 85-100
term 85
>1 mo 75
3 mo - adult 70

Back 7

polycythemia Hg > 22

OR

Hct > 65% during the first week of life

exponential increase in blood viscosity higher HCT

infants of diabetic mothers, toxemia, SGA infants

Hint 7

treated by partial exchange with fresh whole blood or 5% albumin

use central hcts vs capillary Hcts.

Front 8

Newborn Jaundice

newborn bilirubin peaks when

Back 8

day 3 of life and stays elevated to about day 10.

breast fed have higher bilirubin levels 1-2.

Hint 8

<1500
1500-2000
2000 +