Fluids, Electrolyte, and Nutrition

Management in Neonates

N. Ambalavanan MD

Neonatologist

October 1998

www.similima.com 1

FEN Management in Neonates

Essentials of life:

Food (Nutrition)

water (Fluid/electrolyte)

shelter (control of environment - temperature etc)

Essentials of neonatal care:

Fluid, electrolyte, nutrition management (All babies)

Control of environment (All babies)

Respiratory /CVS/CNS management (some babies)

Infection management (some babies)

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Why is FEN management

important?

Many babies in NICU need IV fluids

They all don’t need the same IV fluids (either in quantity or composition)

If wrong fluids are given, neonatal kidneys are not well equipped to handle them

Serious morbidity can result from fluid and electrolyte imbalance

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Fluids and Electrolytes

Main priniciples:

Total body water (TBW) = Intracellular fluid (ICF) + Extracellular fluid (ECF)

Extracellular fluid (ECF) = Intravascular fluid (in vessels : plasma, lymph) + Interstitial fluid (between cells)

Main goals:

Maintain appropriate ECF volume,

Maintain appropriate ECF and ICF osmolality and ionic concentrations

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Things to consider:

Normal changes in TBW, ECF

All babies are born with an excess of TBW, mainly ECF, which needs to be removed

Adults are 60% water (20% ECF, 40% ICF)

Term neonates are 75% water (40% ECF, 35% ICF) : lose 5-10 % of weight in first week

Preterm neonates have more water (23 wks: 90%, 60% ECF, 30% ICF): lose 5-15% of weight in first week

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Things to consider:

Normal changes in Renal Function

Adults can concentrate or dilute urine very well, depending on fluid status

Neonates are not able to concentrate or dilute urine as well as adults - at risk for dehydration or fluid overload

Renal function matures with increasing:

gestational age

postnatal age

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Things to consider:

Insensible water loss (IWL)

“Insensible” water loss is water loss that is not obvious (makes sense?): through skin (2/3) or respiratory tract (1/3)

depends on gestational age (more preterm: more IWL)

depends on postnatal age (skin thickens with age: older is better --> less IWL)

also consider losses of other fluids: Stool (diarrhea/ostomy), NG/OG drainage, CSF (ventricular drainage), etc

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Assessment of fluid and

electrolyte status

History: baby’s F&E status partially reflects mom’s F&E status (Excessive use of oxytocin,

hypotonic IVF can cause hyponatremia)

Physical Examination:

Weight: reflects TBW. Not very useful for intravascular volume (eg. Long term paralysis and

peritonitis can lead to increased body weight and increased interstitial fluid but decreased intravascular volume. Moral : a puffy baby may or may not have

adequate fluid where it counts: in his blood vessels)

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Assessment of fluid and

electrolyte status (contd.)

Physical Examination (contd.)

Skin/Mucosa: Altered skin turgor, sunken AF, dry mucosa, edema etc are not sensitive indicators in babies

Cardiovascular:

Tachycardia can result from too much (ECF excess in CHF) or too little ECF (hypovolemia)

Delayed capillary refill can result from low cardiac output

Hepatomegaly can occur with ECF excess

Blood pressure changes very late

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Assessment of fluid and

electrolyte status (contd.)

Lab evaluation:

Serum electrolytes and plasma osmolarity

Urine output

Urine electrolytes, specific gravity (not very useful if the baby is on diuretics - lasix etc), FENa

Blood urea, serum creatinine (values in the first few days reflect mom’s values, not baby’s)

ABG (low pH and bicarbonate may indicate poor perfusion)

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Management of F&E

Goal: Allow initial loss of ECT over first week (as reflected by wt loss), while maintaining normal intravascular volume and tonicity (as reflected by HR, UOP, lytes, pH). Subsequently, maintain water and electrolyte balance, including requirements for body growth.

Individualize approach (no “cook book” is good enough!)

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Management of F&E (contd.)

Total fluids required:

TFI = Maintenance requirements (IWL+Urine+Stool water) + growth

In the first few days, IWL is the largest component

Later, solute load increases (80-120 Cal/kg/day = 15-20 mOsm/kg/day => 60-80 ml/kg/day to excrete wastes)

Stool: 5-10 cc/kg/day

Growth: 20-25 cc/kg/day (since wt gain is 70% water)

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Management of F&E (contd.)

Guidelines for fluid therapy

Birth Wt(kg)

Dextrose(%)

Fluid rate (ml/kg/d)

<24 hr 24-48 hr >48 hr

<1.0 5-10 100-150 120-150 140-190

1.0-1.5 10 100-120 100-120 120-160

>1.5 10 60-80 80-120 120-160

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Management of F&E (contd.)

Factors modifying fluid requirement: Maturity--> Mature skin --> reduces IWL

Elevated temperature (body/environment)--> increases IWL

Humidity: Higher humidity--> decreases IWL up to 30% (over skin and over respiratory mucosa)

Skin breakdown, skin defects (e.g. omphalocele)--> increases IWL (proportional to area)

Radiant warmer --> increases IWL by 50%

Phototherapy --> increases IWL by 50%

Plastic Heat Shield --> reduces IWL by 10-30%

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Let there be lytes!

Electrolyte requirements:

For the first 1-3 days, sodium, potassium, or chloride are not generally required

Later in the first week, needs are 1-2 mEq/kg/day (1 L of NS = 150+ mEq; 150

cc/kg/day of 1/4 NS = 5.9 mEq/kg/day which is too

much)

After the first week, during growth, needs are 2-3 or even 4 mEq/kg/day

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F&E in common neonatal

conditions

RDS: Adequate but not too much fluid. Excess leads to

hyponatremia, risk of BPD. Too little leads to hypernatremia, dehydration

BPD: Need more calories but fluids are usually

restricted: hence the need for “rocket fuel”. If diuretics are used, w/f ‘lyte problems. May need extra calcium.

PDA: Avoid fluid overload. If indocin is used, monitor

urine output.

Asphyxia: May have renal injury or SIADH. Restrict

fluids initially, avoid potassium. May need fluid challenge if cause of oliguria is not clear. www.similima.com 16

Common ‘lyte problems

Sodium:

Hyponatremia (<130 mEq/L; worry if <125)

Hypernatremia (>150 mEq/L; worry if >150)

Potassium:

Hypokalemia (<3.5 mEq/L; worry if <3.0)

Hyperkalemia > 6 mEq/L (non-hemolyzed)

(worry if >6.5 or if ECG changes )

Calcium:

Hypocalcemia (total<7 mg/dL; i<4)

Hypercalcemia (total>11; i>5) www.similima.com 17

Sodium stuff :

Hyponatremia

Sodium levels often reflect fluid status rather than sodium intake

ECF Excess Excess IVF, CHF,

Sepsis, Paralysis

Restrict fluids

ECF Normal Excess IVF, SIADH,Pain, Opiates

Restrict fluids

ECF Deficit Diuretics, CAH, NEC

(third spacing)

Increase

sodium intakewww.similima.com 18

Sodium stuff :

Hypernatremia

Hypernatremia is usually due to excessive IWL in first few days in VLBW infants (micropremies). Increase fluid intake and decrease IWL.

Rarely due to excessive hypertonic fluids (sod bicarb in babies with PPHN). Decrease sodium intake.

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Potassium stuff

Potassium is mostly intracellular: blood levels

do not usually indicate total-body potassium

pH affects K+: 0.1 pH change=>0.3-0.6 K+

change (More acid, more K; less acid, less K)

ECG affected by both HypoK and HyperK:

Hypok:flat T, prolonged QT, U waves

HyperK: peaked T waves, widened QRS, bradycardia, tachycardia, SVT, V tach, V fib

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Hypo- and Hyper-K

Hypokalemia:

Leads to arrhythmias, ileus, lethargy

Due to chronic diuretic use, NG drainage

Treat by giving more potassium slowly

Hyperkalemia:

Increased K release from cells following IVH, asphyxia, trauma, IV hemolysis

Decreased K excretion with renal failure, CAH

Medication error very common

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Management of Hyperkalemia

Stop all fluids with potassium

Calcium gluconate 1-2 cc/kg (10%) IV

Sodium bicarbonate 1-2 mEq/kg IV

Glucose-insulin combination

Lasix (increases excretion over hours)

Kayexelate 1 g/kg PR (not with sorbitol! Not to give PO for premies!)

Dialysis/ Exchange transfusion

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Calcium stuff

At birth, levels are 10-11 mg/dL. Drop normally over 1-2 days to 7.5-8.5 in term babies.

Hypocalcemia:

Early onset (first 3 days):Premies, IDM, Asphyxia If asymptomatic, >6.5: Wait it out. Supplement calcium if <6.5

Late onset (usually end of first week)”High Phosphate” type: Hypoparathyroidism, maternal anticonvulsants, vit. D deficiency etc. Reduce renal phosphate load

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Things we aren’t going to

discuss (i.e.) homework:

Acid-base disorders: Acidosis or Alkalosis, Metabolic or Respiratory or Mixed

Hypercalcemia

Magnesium disorders

Metabolic disorders

Methods of feeding: Continuous vs. Intermittent; TP vs OG vs NG vs NJ; Trophic feeds; Complications of TPN

(We can discuss these, if time permits) www.similima.com 24

Common fluid problems

Oliguria : UOP< 1cc/kg/hr. Prerenal, Renal, or

Postrenal causes. Most normal term babies pee by 24-48 hrs. Don’t wait that long in sick l’il babies! Check Baby, urine, FBP. Try fluid challenge, then lasix. Get USG if no response

Dehydration: Wt loss, oliguria+, urine sp.

gravity >1.012. Correct deficits, then maintenance + ongoing losses

Fluid overload: Wt gain, often hyponatremia.

Fluid+ sodium restriction www.similima.com 25

Nutrition

Goals: Normal growth and development (as compared to intrauterine growth for preterm

neonates, or as compared to growth charts for

term neonates)

Nutrient requirements:

Energy (Cals) Carbohydrate

Water Minerals

Protein Vitamins

Fat Trace elements www.similima.com 26

Energy { E = mc2

}

Energy needs: depend upon age, weight,

maturation, caloric intake, growth rate, activity, thermal environment, and nature of feeds.

Growing premies: (Cal/kg/day)

Resting expenditure: 50

Minimal activity: 4-5

Occasional cold stress: 10

Fecal loss (10-15%): 15

Growth (4.5 Cal/g +): 45

125

E=energy required

m =mass of baby

c = cry loudness

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Energy

Stressed and sick infants need more energy (e.g. sepsis, surgery)

Babies on parenteral nutrition need less energy (less fecal loss of nutrients, no loss for absorption): 70-90 Cal/kg/day+ 2.4-2.8 g/kg/day Protein adequate for growth

Count non-protein calories only! Protein to be preferred used for growth, not energy

65% from carbohydrates, 35% from lipids ideal

>165-180 Cal/kg/day not useful www.similima.com 28

Calculations

To calculate a neonate’s F,E,& N:

First calculate the amount of fluid (Water)

Then calculate how you plan to give it: Parenteral (IV) or Enteral (OG/PO)

Then calculate the amount of energy required

Decide how to provide the energy: amount and nature of carbohydrates and lipids

Provide proteins, vitamins, trace elements www.similima.com 29

Calculations: practical hints

for TPN

Do not starve babies! The ones who don’t complain are the ones who need it the most.

Use birthweight to calculate intake till birthweight regained, then use daily wt

Start TPN on 2nd or 3rd day if the baby will not be on full feeds by a week

Start with proteins (1 g/kg/d) and increase slowly.

After a few days (3rd or 4th day), add lipids (0.5 kg/kg/d)

Aim for 90-100 Cal/kg/day with 2.5-3 g/kg/d Protein (NPC/N of 150-200)

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Carbohydrate

IV:

Dextrose 3.4 Cal/g = 34 Cal/100 cc of D10W.

Tiny babies are less able to tolerate dextrose. If < 1 kg, start at 6 mg/kg/min. If 1-1.5 kg, start at 8 mg/kg/min.

If blood levels >150-180 mg/dL, glucosuria=> osmotic diuresis, dehydration

Insulin can control hyperglycemia

Hyper- or hypo-glycemia => early sign of sepsis

Avoid Dextrose>12.5% through peripheral IV www.similima.com 31

Carbohydrate

Enteral:

Human milk/ 20 Cal/oz formula = 67 Cal/100 cc

Lactose is carbohydrate in human milk and term formula. Soy and lactose free formula have sucrose, maltodextrins and glucose polymers

Preterm formula has 50% lactose and 50% glucose polymers (lactase level lower in premies, but glycosidases active)

Lactose provides 40-45% of calories in human milk and term formula

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Fat

Parenteral:

20% Intralipid (made from Soybean) better than 10%

High caloric density (2 Cal/cc vs 0.34 for D10W)

Start low, go slow (0.5-3 g/kg/day)

Avoid higher amounts in sepsis, jaundice, severe lung disease

Maintain triglyceride levels of < 150 mg/dL. Decrease infusion if >200-300 mg/dL.

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Fat

Enteral:

Approximately 50% of the calories are derived from fat. >60% may lead to ketosis.

Medium-chain triglycerides (MCT) are absorbed directly. Preterm formula have more MCT for this reason.

At least 3% of the total energy should be supplied as EFA

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Protein

Term infants need 1.8-2.2 g/kg/day

Preterm (VLBW) infants need 3-3.5 g/kg/day (IV or enteral)

Restrict stressed infants or infants with cholestasis to 1.5 g/kg/day

Start early - VLBW neonates may need 1.5-2 g/kg/day by 72 hours

Very high protein intakes (>5-6 g/kg/day) may be dangerous

Maintain NP Calorie/Protein ratio (at least 25-30:1) www.similima.com 35

Minerals (other than Na,K, Cl)

Calcium & Phosphorus:

Third trimester Ca accretion (120-150mg/kg/day) and PO4 (75-85 mg/kg/day) is more than available in human milk. Hence, HMF is essential. Premie formula has sufficient Ca/PO4. Ratio should be 1:7:1 by wt.

Magnesium: sufficient in human milk & formula

Iron: Feed Fe-fortified formula. Start Fe in breast fed term infants at 4 months of age, and in premies once full feeds are reached. (Does not prevent Anemia of Prematurity )

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Vitamins

Fat soluble vitamins: A, D, E, K

Water soluble vitamins: Vitamins B1,B2, B6, B12, Biotin, Niacin, Pantothenate, Folic acid, Vitamin C

All neonates should get vit K at birth

Term neonates: No vitamin supplement required, except perhaps vit D

Preterm: Start vitamin supplements once full feeds established if on human milk without HMF. No need if on human milk with HMF, or preterm infant formula (except: add vit D if on SSC24).

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Trace elements

Zinc, Copper, Selenium, Chromium, manganese, Molybdenum, Iodine

Most preterm formulas contain sufficient amounts

Fluoride supplementation not required in neonatal period

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Special formula

Soy formula:

Not recommended for premies: impaired mineral and protein absorption; low vitamin content

Used if galactosemia, CMPI, secondary lactose intolerance following gastroenteritis

Pregestimil: (Alimentum is similar, but with sucrose)

Hydrolyzed casein; 50% MCT; glucose polymers

Used if malabsorption or short bowel syndrome

Portagen:

Casein; 75% glucose polymers+25% sucrose; 85% MCT

Useful for persistent chylothorax. Can cause EFA def. www.similima.com 39

Special formula (contd.)

Similac PM 60/40:

Low sodium and phosphate; high Ca/PO4 ratio

Used in renal failure, hypoparathyroidism

Similac 27:

High energy with more Protein, Ca/Po4, Lytes

Used for fluid restricted infants: CHF, BPD

Nutramigen:

Hypoallergenic, lactose and sucrose free

Used for protein allergies, lactose intolerance www.similima.com 40