Parenteral Nutrition in Ruminants
Because of cost, use of PN is usually limited to calves, and little information exists on the use of PN in the adult bovine or ovine and caprine species.
Parenteral Nutrition for Foals and Calves
Because of their poor energy stores, early nutritional supplementation is critical in inappetant neonates.
A dextrose infusion■ TABLE 50.6
Parenteral Nutrition Formulation for Adult Horses
| Ingredient | Dosage Rate | Volume/Day (450-kg Horse) |
| 50% Dextrose | 2.8 g/kg/day | 2500 mL |
| 10% Amino acidsa | 1.3 g/kg/day | 6000 mL |
| 10% Lipidb | 0.8 g/kg/day | 3500 mL |
aFreAmine III, Braun Medical Inc., Irvine, CA.
bLiposyn III, Hospira Inc., Lake Forest IL, or 20% Lipid solution: Nutrilipid B, Braun Medical Inc., Irvine, CA.
Ratio of dextrose—amino acids—to-lipid is 1 : 2.4 : 1.4.
■ TABLE 50.7
■ BOX 50.1
Parenteral Nutrition Formulation for Foals (50 kg)
| Ingredient | Dosage Rate | Volume/Day (50-kg Foal) |
| 50% Dextrose | 8.7 g/kg/day | 870 mL |
| 10% Amino acids | 3.0 g/kg/day | 1500 mL |
| 10% Lipid | 1 g/kg/day | 500 mL |
can be instituted initially while determining the health and function of the gastrointestinal tract.
The placenta is reported to supply approximately 4 to 8 mg/kg min of glucose (~25% to 50% DEr), and this is a useful target when providing shortterm parenteral support with dextrose.58 This would equate to 4 to 8 mL of a 5% dextrose solution per minute. Glucose infusion alone is inadequate as a long-term nutritional source; therefore more complete PN is needed for prolonged intolerance to enteral feeding.The initial target energy intake for a critically ill neonatal foal or calf is 40 to 50 mg/kg. Hypertriglyceridemia (>200 mg/ dL) has been associated with higher mortality in neonatal foals.46 To limit complications, lipid calories should comprise less than 50% of the nonprotein calories in a PN formulation.
A PN formulation designed with 8.7, 3.0, and 1 g of dextrose, amino acid, and lipid, respectively, per kilogram body weight (BW) per day provides a total energy of 50 kcal/kg BW/day, a calorie-to-nitrogen ratio of 104: 1, and an osmolarity of 1260 mOsm/L (Table 50.7). The PN formulation contains 21% calories from protein, 20% calories from lipid, and 59% calories from dextrose, with lipid comprising 25% of the nonprotein calories. If the foal or calf tolerates the full infusion rate, more calories can be added from all ingredients to achieve a recipe that provides 70 to 100 kcal/kg BW/day. An anabolic state can be achieved solely with PN therapy, but because enteral feeding is the desired goal, EN or oral milk consumption should begin as soon as possible. Changes in the rate of infusion and the PN formulation should be made to prevent hyperglycemia, but insulin can be administered if necessary to maintain blood glucose in a normal range.
The most common indication for the use of PN in calves is diarrhea, particularly in chronic cases accompanied by weight loss.59 In such cases, if sufficient milk is fed to meet the calf's nutritional needs, the diarrhea is often exacerbated and PN allows the quantity of milk to be reduced without compromising the nutritional status of the patient.
The PN regimen provided for foals in Table 50.7 would also be suitable for calves. However, because amino acids and lipids are the most expensive components of PN, a modified formula based on a 10 : 2 : 1 glucose- to-amino acid—lipid ratio has been used with success.26 For a 50-kg calf, this would allow the quantity of milk to be reduced without compromising the nutritional status of the patient. B vitamin or multivitamin products may be added to the formula (≈1 mL of supplement/L PN), but trace minerals are not usually necessary for the short-term administration that is most common in calves.Preparation and Administration of Parenteral Nutrition (Box 50.1)
Preparation of PN should be performed under a laminar flow hood (or a clean surface away from drafts or excessive dust) using aseptic techniques. Lipids should be added last to prevent destabilization of the emulsion in acidic amino acid solutions. Parenteral solutions are an excellent media for growth of bacteria and ideally should be used within 24 hours of preparation. Before use, they should be kept in a dark, cool area away from direct sunlight to minimize degradation and loss of
Instructions for Compounding a Parenteral Nutrition Solution
1. Compound the solution in a laminar flow hood, if available. Use a clean room in the hospital if a laminar flow hood is not available.
2. Clean the preparation area well, using alcohol as a final preparation on the counter.
3. Wear a gown, mask, and sterile gloves when compounding the parenteral nutrition (PN) solution.
4. Wipe off all injection sites and infusion ports with alcohol before connecting the infusion lines.
5. Use a new transfer set for each PN ingredient.
6. Add the dextrose and amino acid solution to the compounding bag or container. Mix gently.
7. Add the lipid solution after the dextrose and amino acid solutions have been mixed together.
8. Gently swirl the solution to mix the ingredients.
9.
Add any vitamin or mineral supplements to the solution after the macronutrients (dextrose, amino acid, lipid) have been added. Ensure that there are no incompatibilities with the supplemental additives.10. The PN formulation can be stored in the refrigerator for 24 hours, followed by 24 hours of storage at room temperature. Shield the solution from sunlight.
vitamins (when these have been added to the solution). Over time, lipid emulsions will destabilize and oxidize, so they should not be stored for prolonged periods. The shelf life of a lipid solution will vary depending on the type of lipids and size of the emulsion, so manufacturers' recommendations should be used when determining shelf life. Because PN solutions are hyperosmolar, delivery through a central venous or jugular catheter is recommended. Because of the increased risk of sepsis associated with parenteral feeding, a separate catheter or portal should be designated for PN only. In the authors' clinic, a 14-gauge double-lumen catheter (Arrow Catheter, Reading, Pa.) is used with one port designated for administration of PN. Catheter placement and line maintenance should be performed using strict aseptic technique, and it is currently recommended that all lines be changed daily and that connections should not be broken after changes. Administration of PN solutions should not be stopped suddenly; if the animal needs to be moved, it is best to continue administration during the transfer. Gradual introduction of PN is recommended to decrease the risk of complications. It is recommended to use an intravenous infusion pump to ensure that the rate of infusion is consistent. We generally start with an infusion rate targeting approximately 25% of the daily requirement. The most common complication associated with PN is hyperglycemia, and blood glucose concentrations should be determined before increasing the rate of infusion. If blood glucose levels are within reference ranges, then the rate can be increased by an additional 25% every 4 to 8 hours. In the authors' experience most patients will develop mild hyperglycemia that corrects without treatment. Patients with persistent hyperglycemia may require insulin infusions to control the hyperglycemia and allow continued infusion.