Nutrition in the Neonate

Importance of Nutrition in Early Life Critical periods in fetal and neonatal life which may result in long lasting effects in adulthood Examples: Inverse relationship between Birth weight and mortality from coronary artery disease as adult. Infants < 5.5lbs have 2x risk of cardiac mortality & hypertension vs 8-9lb. Infants >9lb increased cardiovascular risk and obesity. Breast feeding resulting in lower cholesterol levels and lower systolic blood pressure, and protective against childhood obesity

Gastrointestinal Tract in Premature Infant Intestinal tract elongates 1000x during 5-40 weeks gestation- doubles in length during last 15 weeks to 275 cms at birth. Fetal swallowing: 450ml/day in 3rd trimester. Fluid includes growth factors. Availability interrupted by premature birth Gastro-esophageal tone is decreased Motility is delayed

Nutrition Requirements Growth rate after birth is much slower than in-utero Undernourished at a vulnerable time Protein and energy must be provided in appropriate proportion for optimal utilization of each Nutrient intakes must meet needs for deposition and replacement of ongoing losses Protein is continuously lost via skin as desquamated cells and as urea Resting metabolic rate is increased with prematurity, disease states, and low birth weight

Neonatal Energy Form of Energy Caloric Expenditure Resting Metabolic Rate* 50 kcal/kg/day Activity 15 kcal/kg/day Cold Stress 10 kcal/kg/day Nutrition Processing 50 kcal/kg/day Total 120 kcal/kg/day Processing indicates excretion, storage, and synthesis. Resting metabolic rate is increased with prematurity, disease states, and low birth weight Most sources recommend caloric requirement of 120-150kcal/kg/day to balance energy expenditure Assumption is that postnatal growth should mirror in utero growth of a fetus at the same postconceptual age Activity accounts for only 10% since infants sleep 80-90% of the time but this can increase with agitation Ideally the preterm infant should grow the same as the fetus in utero 15-20 g/kg/day

Nutrition Requirements- Carbohydrates Primary energy substrate for brain metabolism Hepatic glycogen content is limited Gluconeogenesis (production of glucose from amino acids and lipid oxidation) is large contributor to glucose production Glucose regulatory hormones and enzymes are not fully developed Increased risk for hypoglycemia Hyperglycemia: exceeding normal glucose turnover rates; stress; relative insulin deficiency; hepatic peripheral insulin resistance Very preterm infants have poor glycogen stores and decreased substrates for gluconeogenesis, thus are vulnerable to developing hypoglycemia

Nutrition Requirements- Lipids Source of essential Fatty Acids and LCPUFA Linoleic and linolenic acid comprise cell membranes LC-PUFA (AA & DHA) important for brain and retinal development Energy substrate readily utilized by VLBW Decreases amino acid oxidation and protein breakdown when lipid provides 50% of non-protein calories Provides greater energy and is isotonic compared to high concentration dextrose AA: arachidonic acid DHA: docosahexaenoic acid

Benefits of Early Parenteral Nutriton Provides nutritional support and supplements enteral feedings as the gut is adapts and matures Greater weight, length, and head circumference percentiles at discharge Improved long term neurodevelopmental outcome The nutritional support of extremely low birth weight infants is almost entirely dependent on parenteral nutrition. There is growing evidence that early use of TPN may minimize losses and improve growth outcomes.

Indications for TPN Prematurity < 1500 grams GI anomalies or surgery Feeding intolerance / ileus Necrotizing enterocolitis Cardiac disease Chronic diarrhea Pulmonary disease Severe asphyxia TPN indicated in all infants for which enteral feeds is contraindicated or delivers < 75% of requirements ENTERAL is always preferred route of nourishing babies. TRophic feeds promote ongoing maturity of the GI tract, avoid villous atrophy from disuse, and promote release of gut hormones.

Benefits of Early Enteral Nutrition Stimulates gut maturation Increases gut hormone release Improves gut motility Prevents gut atrophy Decreased release of proinflammatory mediators Shortens time to achieving full feedings Decreases length of hospitalization Does not lead to an increased incidence of NEC

Feeding Premature Infants Birth Weight 500–1250g: Start at 10-20 mL/kg/d x 3-5 days, then increase by 10-20 mL/kg/day Birth Weight 1250g up to gestation 34 6/7 wks: Start at 20-30 mL/kg/d x 1 day, then Increase by 20-30 mL/kg/d. Note that nippling babies may be advanced more quickly Gestation > 35 wks: Treat as full term For all weights: Change to 22 kcal/oz at 80 mL/kg/d Change to 24 kcal/oz at 100 mL/kg/d Consider making no volume increases on days when caloric density changed D/C IL at 100-120 mL/kg/d D/C HA and DL at 120 mL/kg/d

Advantages of Human Milk for VLBW Infants Quality of protein Trophic effects on the developing GI tract Rapid gastric emptying Human milk Lipase LCPUFA

Nutritional Goals Provide sufficient energy and nitrogen to prevent catabolism and to achieve positive nitrogen balance Maintain postnatal growth at normal rate: (15-30 grams/day) Non protein caloric intake of 60 cal/k/d with an AA intake of 2.5-3 gm/k/d can achieve an anabolic state; 80-85 cal/k/d with same AA concentration can result in nitrogen retention at fetal rate Essential components are carbohydrates,electrolytes, protein, lipids, vitamins, trace minerals Ultimate goal is to deliver 100-110 cal/k/d using dextrose, amino acids and lipids Initial goal is to provide sufficient energy and nitrogen to prevent catabolism and to achieve a positive nitrogen balance. Calories provided by CHO and fat. TPN should provide suffient protein for protein turnover and tissue growth. Caloric intake of 50-60 kcal/kg/day approximates energy expenditure---reasonable goal for 1st few days of life. However, to support normal rates of growth during TPN, 90-100kcal/kg/day are required. Most of these calories are supplied by lipid and glucose. Energy requirements for the sick VLBW infant may be higher.

Nutritional Goals Non nitrogen calories: 65kcal/kg/day by 5 days Combined enteral and parenteral nutrition: 100-130kcal/kg/day

Calculation of Calories Calculation of non-nitrogen calories: Dextrose 3.4kcal/gram 20% intralipid 2kcal/ml Protein 4 cal/gram Glucose infusion rate: 6-8mg/kg/min GIR: 0.167 x concentration x rate weight Most calories are provided by lipid and glucose.

TPN: Carbohydrates Carbohydrates Exclusively glucose With increased glucose concentration, there is increased osmolarity Should provide 55-65% of total kilocalories Maximum concentration is 12.5% peripherally Begin with glucose infusion rate (GIR) of 6 mg/kg/min and gradually advance to 10-12 mg/kg/min GIR: 0.167 x concentration x rate weight Glucose is most readily available to the brain.

TPN: Protein Goal is to prevent negative energy and nitrogen balance High rates of protein turnover supply protein synthesis, tissue remodeling, and growth Early initiation of protein reverses negative nitrogen balance. Should provide 7-10% of total calories Failure to provide adequate protein can have a serious impact on the long term outcome of extremely premature infants.

TPN: Lipids Essential fatty acid deficiency avoided with use of 0.5-1 gm/kg/day Provides additional energy Should provide 30-50% of total calories Limit to 3 g/kg/day Infuse over 20 hours Monitor serum TG levels (accept < 150 mg/dL)

Daily Requirements of TPN Calories 90-110kcal/kg or as needed H20 125-150 ml/kg or as needed Protein 2.5-4 gm/kg Lipid 2.4 gm/kg

Daily Requirements of lytes, vitamins and minerals Na 3-4 mEq/kg K 2-3 mEq/kg Ca 50-100mg/kg Phosphorus 1-1.5 mM/kg Magnesium 0.5-1mEq/kg Multivitamins 10ml (40%/kg/day) Trace elements 1mL/kg/day (Copper, zinc, chromium, manganese) Zinc 400mcg/kg/day (prematures) 250 mcg/kg/day (term<3mos) 100 mcg/kg/day (term >3mos) Selenium 1-2 mcg/kg/day Carnitine 10mg/kg/day Extremely important to provide sufficient Ca/Phos to prevent bone demineralization

TPN: Practical Approach Begin starter TPN in all preemies <1800g Begin TPN within 24 hours of delivery Dextrose: Begin with 4-6 mg/kg/min and advance to 10-12 mg/kg/min. Amino acids: Begin with 2 gm/kg/day and advance by 1gm/kg daily to max of 4 gm/kg/day. Lipids: Begin with 0.5 gm/kg/day and advance gradually to max of 3 gm/kg/day. Assess glucose tolerance.

Parenteral Nutrition Weaning After enteral feeds have been established and tolerated, begin to decrease parenteral nutrition for total fluid 120-150 ml/k/d. When enteral feeds reach ~80 ml/k/d, discontinue Intralipids and fortify feeds to 22 cal/oz. At ~100 -120 ml/k/d of enteral intake discontinue parenteral nutrition and central line.

Monitoring Monitor daily weights Monitor head circumference, length weekly Monitor Lytes, Ca as needed. Monitor phos, Mg, albumin, BUN, Cr, total and direct bili, SGPT, alk phos, triglyceride weekly Consider: zinc, copper, carnitine, and selenium levels at 2-3 months

Complications of TPN Catheter related: Thrombus (SVC syndrome, chylothorax) Infection Extravasation (pleural and pericardial effusions) Air or fat embolus Infiltration with tissue injury

Complications of TPN Metabolic: Electrolyte imbalance Hypo-hyperglycemia Hyperlipidemia Trace mineral and Vit deficiency Cholestasis Osteopenia

Etiologies of Inadequate Growth Actual intake too low Volume of intake not increased for weight gain Fore milk feedings Human milk fortifier not added in correct proportions Low sodium Low protein intake Weaning from incubator too rapidly