NICU:  Fluids, Electrolytes, Nutrition

Initial Fluids
TPN Components
Calorie Calculations
Enteral Feeds

Initial Fluids

Initial Fluid Orders:

Usual starting fluid composition is D₁₀W with 3 mEq/kg/day of Na, 2 mEq/kg/day of K and 1 mEq/kg/day of Ca (as calcium gluceptate)
Take total fluids in cc/kg/day and multiply by weight (kg) and divide by 24 hours to get the hourly rate.
If a UAC is in place, give 2 cc/hour of D₁₀W with 0.5 units heparin per cc via UAC.
Give the remaining fluid by UVC or PIV is no UVC is present.
 

Example Fluid Orders

Weight = 0.9 kg  Total fluid = 100 cc/kg/day:  UVC fluid = D10W with the following electrolytes to run at 2.6 cc/hour.    Na 3 mEq/kg/day K 2 mEq/kg/day Ca 1 mEq/kg/day    UAC:  Please run D10W with 0.5 units heparin per cc at 2 cc/hour.

 
Check electrolytes, BUN, glucose, calcium at 12 hours of life, then q 12 hours
Serum electrolytes prior to 12 hours are reflective of maternal values

TPN Components (also see Parenteral Nutrition Recommendations)

Dextrose (glucose):  Start with the dextrose concentration from the previous IVF.  You may increase dextrose by 2.5% daily as long as significant hyperglycemia is not present.  Higher serum glucose levels may be acceptable (140s-150s) as long as no more than trace glucouria is present.  Maximum dextrose concentration in PIC is 12.5%; maximum in central line (UVC or Broviac) is that which gives 12-15 mg/kg/min of dextrose (usually D₂₀ to D₂₅).
 
 

Acetate:  Converted by the liver to bicarbonate.  The dose is based on the bicarbonate value from daily electrolytes.  As the amino acid dose increases, more acetate is required.  Since bicarbonate is converted to carbon dioxide, ventilation must be adequate.  Usual dose is 0.5 - 1 mEq/kg/day, but this is highly variable from patient to patient.

Electrolytes: (refer to table of basic maintenance electrolytes).  In addition to Na, K and Ca, PO₄ (0.5 to 1 mmol/kg/day) and Mg (0.2 to 0.5 mEq/kg/day).

Try to keep the Ca:PO₄ ratio of around 2:1 (mEq:mmol).  If ratio is less than this, salts may precipitate and pharmacy will advise that lower concentrations be used.
Check calcium daily at first.  Check Mg twice weekly and make changes as needed.  Minor changes in TPN will be made based on daily electrolytes.  Check a chem-20 weekly for electrolytes, LFTs, and triglycerides.  Elevation of LFTs are known complications of TPN therapy.

Caloric Calculations

Dextrose:  Recall that percent dextrose is grams of dextrose per 100 cc, and the energy content is 4 kcal/gram.  To calculate the energy yield from IV dextrose, multiply the percentage dextrose by the volume (per kg/day) by 0.034
 

For a 3 kg patient who received 300 cc of D12,  100 cc * 12 % * 0.034 = 40.8 kg/kg/day from glucose.

 
Protein:  Although amino acids can be catabolized as an energy substrate, this energy is not usually included in the daily energy yield because the intention is for them to be used as a building block for proteins.  To calculate the percentage contribution of fat, protein and carbohydrate, however, it is useful to be able to calculate calories from protein.  Each gram of protein contributes 4 kilocalories.

Lipids:  Every gram of lipid yields 9 kcal:
 

30 cc IL/3 kg * 0.2 g/cc IL * 9 kcal/gram IL = 18 kcal/kg/day

 

Enteral Feeds (also see Enteral Nutrition Recommendations)

Once an infant (premature or otherwise) has achieved clinical stability (especially with respect to hemodynamics and gas exchange), it is often appropriate to begin enteral feedings.  The RR should be less than 60  for oral feeds and less than 80 for nasogastric (NG) feeds.  Ideally, the patient should be without UAC or UVC.  If asphyxia is confirmed or suspected, delay feeding until day of life seven in the term newborn.  If the infant is > 2 kg and > 34 weeks, oral feeds may be tried.  Otherwise, NG feeds are necessary.

To begin feeds, determine the route and what you wish to feed the baby.  For oral feeds, begin with sterile water (optional if the patient is fed by NG.  The method, composition and rate will depend on the weight and gestational age of the patient.
 

>2 kg, > 34 weeks:  Try sterile water first, 5 - 10 cc.  If tolerated, give maternal breast milk (the optimal food for a newborn) or formula (may start with half-strength for smaller or tenuous infants).  For greater than 34 weeks gestation, use regular formula. For less than 34 weeks, use preemie formula  Depending on the weight, begin with 5-15 cc q 2-3 hours and advance by 5-10 cc every (or every other) feeding until the total daily fluid goal is comprised of feedings.  If using half-strength formula, feeds can be advanced to full strength by the second day of feeds.  Remember to decrease IVF or TPN as feeds are increased to maintain a constant fluid intake.

< 2 kg, < 34 weeks:  usually NG feeds are required since these babies usually lack an adequately coordinated suck-swallow reflex.  One way to begin is with continuous feeds of MBM or half strength premie formula.  As rough guidelines: start with 0.5 cc/hour for weight less than 1200 grams, or 0.5 - 1 cc/hour for weight greater than 1200 grams.  If residuals are greater than 5-10 cc, consider holding feeds.  When feeds are begun, follow abdominal girth (AG) every 6-12 hours; follow the abdominal exam closely as well (watch for distension and palpable bowel loops).  If increasing AG, or abnormal abdominal exam, or bloody stools, obtain a flat abdominal and cross-table lateral radiograph immediately.  If tolerated, feeds may be advanced by 0.5 - 1 cc/hour every 4-6 hours until full feeds are reached.  Also, advance to full strength formula by day 2-3 of feeds.  Again, wean TPN/IVF as feeds are increased.
 

Once an infant is tolerating full feeds, the caloric density of the feeds can be increased.  This is expressed as an abbreviation next to the formula which signifies the number of kcal per ounce of formula.  Once ounce = 30 cc.  Thus, 30 cc of breast milk (MBM₂₀) yields 20 kcal. Advance as tolerated: 24 kcal/ounce for 1-2 days, then 27 kcal/ounce for 1-2 days, up to a maximum of 30 kcal per ounce.  Signs of feeding intolerance include increasing abdominal girth and residuals, and frequent, loose stools.  If this occurs, either hold the feeds or decrease the caloric density to a previously tolerated level.
 

For a 3 kg patient who has taken 350 cc of MBM fortified to 24 kcal/ounce with human milk fortifier (HMF):    360 cc/3kg * 24 kcal/30 cc = 96 kcal/kg/day