Parenteral Nutrition for Premature Infants: The Basics
The nutritional needs of very low-birth-weight (<1500 grams [g]) infants are rarely met
by enteral nutrition within the first 2 weeks of life. The premature infant requires 80 to
120 kilocalories (kcal)/kilograms (kg)/day when fed by parenteral nutrition (PN). This is
less than the energy requirement when fed enterally, because the controlled environment
results in less fecal energy loss and lower energy needs for activity and thermoregulation.
The recommended distribution is 30% lipid, 55% carbohydrate, and 15% protein. You
should initiate PN within the first 24 hours after birth to reverse protein loss because of
catabolism.
Hyperglycemia and hypoglycemia
Too much glucose will lead to glucose conversion to fat, which leads to an increased
minute ventilation and respiratory quotient. However, premature infants are at an
increased risk for both hyperglycemia and hypoglycemia. Some infants will require high
glucose infusion rates (5 to 8 milligrams (mg)/kg/minute) to prevent hypoglycemia. The
treatment of hypoglycemia in premature infants is controversial. However, the threshold
is usually 45 to 50 mg/deciliter (dL).
Infants who are born <1000 g are at even higher risk of hyperglycemia for many reasons,
including ineffective insulin secretion, end-organ insulin resistance, decreased glucose
intracellular transporters, elevated catecholamines and glucocorticoids, provision of high
glucose intakes, and an absence of enteral nutrition, which stimulates insulin secretion.
The early initiation of amino acids and lipid infusion in these infants is a way to prevent
hyperglycemia. Hospitals may start glucose infusion for infants born at <1000 g at 3.5
mg/kg/minute and advance the rate daily or as tolerated by 1 to 2 mg/kg/minute to a
maximum of 7 to 12 mg/kg/minute.
An excessively high carbohydrate intake (>18 g/kg/day) can result in net lipogenesis with
hepatic fat deposition and steatosis of the liver. It seems that glucose concentrations of up
to 12.5% are well tolerated through a peripheral vein cannula, as long as no other
osmolarity-increasing agents are added.
Amino acid intake
In premature infants receiving total parenteral nutrition (TPN), a positive nitrogen
balance usually is attainable with an amino acid intake of 3 g/kg body weight/day. In
individual cases, an amino acid intake of up to 3.5 to 4 g/kg body weight/day sometimes
is necessary to achieve protein synthesis according to the intrauterine ratio. One literature
review found that infants receiving ≥4 g/kg/day tolerated the infusion fine and had lower
rates of bronchopulmonary dysplasia, when compared to intake of 3 g/kg/day. It is not yet
known whether supplementing cysteine and/or glutamine to PN is of clinical benefit in
preterm infants. Amino acid imbalances can result in toxic organ damage and may have
involvement in the development of PN-associated cholestasis.
Lipids
Lipids given as early as PN prevent essential-fatty-acid deficiency, provide needed
energy for tissue healing and growth, and balance the distribution of nonprotein calories.
To prevent a deficiency of essential fatty acids, a minimum intake of 0.25 g/kg/day of
linoleic acid is recommended in premature infants. It appears that a 20% intralipid
solution is better tolerated than a 10% solution, because the 10% solution requires a
larger administered volume and is associated with a poorer clearance of triglycerides. If
both are given at the same lipid dose, intermittent infusion appears to produce higher and
more variable serum triglyceride concentrations than continuous infusion.
You should initiate lipids as a continuous infusion of 20% intralipid at a dose of 1
g/kg/day and advance as tolerated to a target of 3 g/kg/day. Chronically ill infants who
are unable to tolerate enteral feedings to meet needs may occasionally receive 4 g/kg/day.
The target for triglycerides is <150 mg/dL.
You should consider a reduction in lipid intake if triglyceride concentrations in serum or
plasma in continuous infusions exceed 250 mg/dL. Caution is recommended in premature
infants weighing <1000 g because tolerance to intravenous (IV) lipid emulsions
sometimes is more limited A theoretical concern is that intralipids increase indirect
hyperbilirubinemia, so some institutions limit the rate to less than 3 g/kg/day in cases of
extreme hyperbilirubinemia.
Phosphorus and calcium
Premature infants are prone to hypocalcemia, phosphate metabolic abnormalities, and
hypermagnesemia. You should add phosphorus first and calcium as the last step during
PN preparation to optimize solubility. You should administer the two minerals together to
optimize bone deposition. In general, the dose of elemental calcium ranges from 25 to 75
mg/kg/day.
You may not need to add phosphorus for the first 24 to 48 hours of life. The optimal ratio
of calcium to phosphorus is 1:1.3=1:1.7 by weight. Oral vitamin D prophylaxis with 1000
international units (IU) vitamin D/day from day 7 of life is sufficient in extremely
premature infants.
Vitamins
Currently marketed vitamins for premature infants do not provide sufficient quantities of
vitamin A. Vitamin A is particularly difficult to provide parenterally to premature infants
without administering excessive quantities of other vitamins. This is because of its loss
through photodegradation and binding to the bag and tubing. The vitamin is best mixed
with intravenous lipid emulsion or given as retinyl esters.
The currently marketed formulations also may provide too much vitamin C and riboflavin
(vitamin B2), although whether or not this has any adverse effects on infants is unknown.
Insufficient thiamine intake can result in severe lactic acidosis within only a few days in
children on PN.
Hydration status
Serum sodium indicates the hydration status of premature infants for the first few days of
life. After the first 24 hours after birth, sodium and potassium are monitored and adjusted
on a daily basis. In general, these infants require 2 to 4 milliequivalents/liter (mEq/L) for
both electrolytes. You should consider intravenous saline infusions and flushes used to
administer medications when calculating the sodium requirements of PN.
Trace minerals
Calculated daily intakes for trace elements are based on the birth weight and intrauterine
accretion rate:
Birth weight ≤2.5 kg
 Zinc: 400 microgram (mcg)/kg
 Copper: 20 mcg/kg
 Chromium: 0.4 mcg/kg
 Manganese:10 mcg/kg
 Selenium: 2 mcg/kg
Birth weight >2.5 kg
 Zinc: 250 mcg/kg
 Copper: 10 mcg/kg
 Chromium: 0.1 mcg/kg
 Manganese: 2.5 mcg/kg
 Selenium: 1.5 mcg/kg
The only trace elements recommended from the first day of PN are zinc and selenium.
Other trace elements are not needed until 2 weeks of age. Iron is not needed in the first
few weeks of life and is not routinely added to PN. Infants with intestinal losses may
require larger amounts of zinc. Copper and manganese are excreted in the bile, so you
should decrease intake in patients with cholestatic syndromes. Selenium is renally
excreted, so you should decrease intake in patients with impaired renal function.
Carnitine is an intermediary in fat metabolism and is imperative for energy production in
tissues dependent upon fatty acid oxidation, such as cardiac and skeletal muscle. Some
experts believe that for preterm infants who require PN for more than 2 weeks that you
should administer parenteral carnitine in doses of 10 to 20 mg/kg/day until adequate
enteral nutrition is initiated. However, a meta-analysis based on 14 randomized
controlled studies showed no effect of carnitine supplementation on the metabolism of
lipids, lipogenesis, or weight gain.
References and recommended readings
Fusch C, Bauer K, Böhles HJ, et al; working group for developing the guidelines for
parenteral nutrition of the German Society for Nutritional Medicine.
Neonatology/paediatrics—guidelines on parenteral nutrition, chapter 13. Ger Med Sci.
2009;7:Doc15. doi:10.3205/000074.
Herrmann KR, Herrmann KR. Early parenteral nutrition and successful postnatal growth
of premature infants. Nutr Clin Pract. 2010;25(1):69-75.
doi:10.1177/0884533609359001.
Pediatric Nutrition Care Manual®. Academy of Nutrition and Dietetics Web site [by
subscription]. www.nutritioncaremanual.org. Accessed April 30, 2013.
Schanler RJ. Parenteral nutrition in premature infants. UpToDate® Web site.
http://www.uptodate.com/contents/parenteral-nutrition-in-premature-infants?view=print.
Updated April 11, 2013. Accessed April 30, 2013.
Review Date 4/13
K-0645