Parenteral Nutrition

Partial or total parenteral nutrition is routinely used and is an integral part of neonatal intensive care. Advances in delivery systems and development of long-term, double or triple lumen intravenous catheters have allowed greater utilization of parenteral nutrition. In contrast to human infants, foals should gain a significant amount of weight daily (1-3 lbs, ≈1 kg) following birth.
Editor's Comment - For quick start of formula used at UC Davis see TPN Straight Talk - simple set up.

I. Indications

1. Neonatal foals that have not been able to consume at least 10% of their body weight in milk for a 48-72 hour period.
2. Neonatal foals that have daily weight loss (even just 1 pound) for 24-48 hours and cannot consume at least 10% of their body weight in milk during next 24 hrs.
3. Premature foals or critically ill foals with gastric reflux and minimal gut motility on day 1 or 2 of life.
   Editor's Comment - Don't wait for weight loss, start TPN and feed only when GI motility returns
4. All neonatal foals that are not gaining daily weight while receiving maximal tolerated amounts of enteral nutrition.

1. Base line, maintenance caloric requirements are 100-150 Kcal/kg/day [1].
2. Resting caloric requirements are (premature or recumbent foal) lower because of the low activity level (50 Kcal/kg/day).

5. Conditions which may require TPN.

1. Prematurity.
2. Severe, persistent diarrhea.
3. Septicemia with secondary ileus.
4. Respiratory distress with secondary ileus.
5. Post-gastrointestinal surgery
6. Persistent gastric obstruction.

6. Effects of protein malnutrition.

1. Decreased immune function.
2. Weakness - Depression - Incoordination.
3. Decubital sores.
4. Angular limb deformities.
5. Failure to grow.

II. General Principles of Parenteral Nutrition

1. Dextrose alone won't meet energy demands.

1. Dextrose provides 3.4 Kcal/gm [1]. 5% dextrose contains 170 Kcal/L.
2. Since resting caloric requirements in a 50 kg foal are approx. 2500 Kcal/day, and 5% dextrose contains 170 Kcal/liter it would take 15 liters of 5% dextrose/day IV to meet this energy demand.
3. Dextrose solutions ≥10% can be irritating to veins. Other problems with hypertonic glucose are hyperglycemia, glucosuria, and fatty liver.

2. Lipids provide 9.0 Kcal/g and essential fatty acids [1].
3. Amino acid solutions can be used as protein source [1].

1. Amino acids in "veterinary jugs" have grossly inadequate levels of amino acids for TPN [1].
2. Use an 8.5% amino acid solution.
3. Must balance ratio of nitrogen with energy; non-protein calories per gm of nitrogen should be 100-200 [1].

4. Solutions of dextrose, protein and lipid can be combined for "all in 1 bag" administration and meet energy and protein requirements for maintenance and growth.
5. Parenteral nutrition requires minimum of 1 day to get started, 1 day on, and 1 day to wean off.
6. Fluid (water) requirements will not be met with these solutions. Foals need approximately 100-120 ml/kg of fluid a day.
7. Always try to feed small amounts enterally if possible while using parenteral nutrition.

III. Administration [2]

1. A dedicated IV port that is not used for giving any other medications or drawing blood samples is required to prevent infection.

1. If medication must be administered through this line, stop TPN solution, wipe injection port with alcohol and 2% iodine and flush with heparinized saline before and after medication administration.

2. Jugular Catheter (See Placement and Management of Intravascular Catheters)

1. Teflon catheters are not recommended and should be avoided for TPN administration. This catheter coupled with a hyperosmotic fluid like TPN carry high risk for thrombosis and catheter-induced sepsis.
2. Polyurethane Single, double or triple lumen Mila®, Arrow®, Cook®, Jorvet® IV catheters with a guidewire or peel away introducers can be used in a size of 4-7FR X 5-10'' (12-25 cm).
   Editor's Comment - Our NICU uses this type preferably triple or at least double lumen catheters.
3. Silicone elastomer catheters (Mila®, Braun®, Arrow®, Cook®) with single or double lumen (60 cm X 5-7Fr) have minimal thrombogenicity and can be left in a central vein for up to 30+ days.

3. Rate of Administration needs to be carefully controlled.

1. A constant flow rate is required.
2. Infusion pumps are essential.
3. A buretral system without pump can be employed but not recommended for extended periods.
4. Target rate should be calculated to meet resting requirements (50 Kcal/kg/day)
5. Start at 25% of the goal rate to allow the physiology to adjust, then gradually increase every 4-6 hours while monitoring blood glucose levels every 4-6 hrs.
6. Solutions are generally increased in volume over 24 hours to reach the target level.
7. Once the target level is tolerated, the rate can be increased to provide 75 Kcal/kg/day.

4. Change all IV lines associated with the TPN solution once daily.
5. Change hanging solutions once daily.

IV. Solutions and Administration [2-4].

Parenteral nutrition solutions should be mixed under a hood, wearing sterile gloves and mask. Alternatively with the Baxter All in One Bag® solutions can be mixed on a disinfected counter in a draft free environment.

1. Partial parenteral nutrition formula.

1. 500 ml of 50% dextrose - Energy.
2. 500 ml 8.5% amino acid solution, 100 ml contains 14.3 gm nitrogen.
3. Provides 1 Kcal/ml.
4. Start at 25 ml/hr and work up to 100 ml/hr over a 24 hour period.
5. Withdraw over 12-24 hours to avoid sudden hypoglycemia.
6. Monitor.

1. Serum glucose BID
2. Urine glucose frequently.
3. Serum K+; watch for hypokalemia.
4. BUN once daily - To assess tolerance to nitrogen.

2. All in one parenteral nutrition - Amino acids, glucose

1. Energy from: 1000 ml of 50% dextrose
2. 500 ml of 20% lipid emulsion.
3. Nitrogen from 1500 ml of 8.5% amino acid solutions.
4. Mix dextrose and amino acids first; then add lipid when using Baxter All in One Bag; or can piggyback lipid solution on Dextrose-AA line.

1. All in One Bag has 3 leads for plugging into each stock solution of amino acids, dextrose and lipids.

5. Start at 25 ml/hr and work up to 100 ml/hr over 24 hours. It provides 1.07 Kcal/ml.

3. Electrolytes can be added to the solutions.

1. I prefer not to add the electrolytes, but drip a KCl solution in another vein and add Na+ and other electrolytes as needed. Severe hypernatremia has developed with adding recommended electrolytes to the TPN.

4. Vitamins and Minerals need to be added to the PN formula

V. TPN Straight Talk-simple Set Up: (Gary Magdesian's favorite TPN recipe)

1 L of 50 % dextrose
1.5 L of 8.5 % amino acids
0.5 L of 20 % lipids
Total volume: 3.0 L of PN. Caloric content is approximately 1.13 kcal/ml. Put it all in one bag.
To provide 50 kcal/kg to a 50 kg foal, approximately 2200 ml are required per day, equating to 91 ml/h. As this is tolerated the PN can be increased to provide approximately 75 kcal/kg/day, or 140 ml/h.
If the animal has lipid derangements, then I leave out the lipids and do:
1 L of 50 % dextrose
1 L of 8.5 % amino acids
This has an energy content of 1.02 kcal/ml
I also supplement vitamins and minerals - B-complex in fluids and a commercial human TPN vitamin mineral mix in the PN solution.
Potassium and calcium and phosphorus can be added as needed. I usually supplement Mg through the use of Mg containing fluids at a maintenance rate. Plasmalyte and Normosol have 4 meq/l of Mg.
Potassium is added to fluids (or PN) at 20-30 meq/l.
Phosphorus can be added at 0.01 mmol/kg/L for an 8-12 h period per day.

VI. Common Problems - Complications [4]

1. Hyperglycemia [1]

1. During the initial 24 hour adaptation, elevated blood sugars of < 200 mg/dl (11 mmol/l) are tolerated.
2. Prolonged hyperglycemia (glucose > 180 mg/dl; 10 mmol/l) can cause fluid loss and other problems. Glucose becomes converted to fat within liver.
3. With severe infection such as septicemia, glucose may not be metabolized at normal rates. Decrease infusion rate of TPN and initiate insulin therapy.
4. May increase metabolism of glucose and cause increased production of CO2 and increase work of breathing.

2. Hyperlipidemia [1]

1. May be observed as gross lipemia.
2. Serum triglyceride (>200 mg/dl; 2.3 mmol/l) and cholesterol may increase.
3. Slow rate and concentration of lipid emulsion from 20% to 10%.

3. Metabolic Acidosis

1. Principal cause is excess chloride in electrolyte solution. As chloride anion increases, HCO3-anion decreases and have base deficit.
2. Lower chloride in supplemental fluids.
3. If acidosis is severe - Correct as described (See Fluid and Electrolyte Balance).

4. Hypokalemia

1. Associated with hyperglycemia (K+ moves intracellularly), or with losses from diarrhea.
2. Supplement with potassium chloride solution in 10-30 mEq/L KCl solutions.
3. Do not exceed flow rates of 0.5 mEq/kg of potassium/hour.

5. Infection

1. Catheter associated or solution contamination.
2. With careful attention to detail this is infrequent.