Fluids, Electrolyte, and Nutrition Management in Neonates

N. Ambalavanan MDNeonatologistOctober 1998

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)

Why is FEN management important?

Many babies in NICU need IV fluidsThey 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

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

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

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

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

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)

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

outputHepatomegaly can occur with ECF excessBlood pressure changes very late

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 bicarb may indicate poor perfusion)

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!)

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)

Management of F&E (contd.)

Guidelines for fluid therapyBirth 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

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%

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

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.

Common ‘lyte problemsSodium:

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)

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)

Increasesodium intake

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.

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

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

Management of Hyperkalemia

Stop all fluids with potassiumCalcium gluconate 1-2 cc/kg (10%) IVSodium bicarbonate 1-2 mEq/kg IVGlucose-insulin combinationLasix (increases excretion over hours)Kayexelate 1 g/kg PR (not with

sorbitol! Not to give PO for premies!)Dialysis/ Exchange transfusion

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

Things we aren’t going to discuss (i.e.) homework:

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

HypercalcemiaMagnesium disordersMetabolic disordersMethods of feeding: Continuous vs.

Intermittent; TP vs OG vs NG vs NJ; Trophic feeds; Complications of TPN

(We can discuss these, if time permits)

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

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) CarbohydrateWater MineralsProtein VitaminsFat Trace elements

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 requiredm =mass of baby c = cry loudness

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

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

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)

CarbohydrateIV:

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

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

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.

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

ProteinTerm infants need 1.8-2.2 g/kg/dayPreterm (VLBW) infants need 3-3.5 g/kg/day

(IV or enteral)Restrict stressed infants or infants with

cholestasis to 1.5 g/kg/dayStart early - VLBW neonates may need 1.5-2

g/kg/day by 72 hoursVery high protein intakes (>5-6 g/kg/day)

may be dangerousMaintain NP Calorie/Protein ratio (at least 25-

30:1)

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 )

Vitamins

Fat soluble vitamins: A, D, E, KWater soluble vitamins: Vitamins B1,B2, B6, B12,

Biotin, Niacin, Pantothenate, Folic acid, Vitamin C

All neonates should get vit K at birthTerm neonates: No vitamin supplement

required, except perhaps vit DPreterm: 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).

Trace elements

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

Most preterm formulas contain sufficient amounts

Fluoride supplementation not required in neonatal period

Special formulaSoy 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.

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