Podcast: Nutrition: parenteral
- Parenteral nutrition is affordable way of providing nutrition to both foals Nutrition: neonate and adults Nutrition: adult.
- It can be used when enteral feeding is not possible, or in conjunction with enteral feeding.
- In foals this would include perinatal asphyxia syndrome, any patient that is refluxing, regardless of their primary condition, those with botulism and dysphagia, and those needing pharyngeal rest, such as those that had surgery to correct a cleft palate.
- In adults it may be indicated in horses with esophageal disease, in colic patients Abdomen: pain - adult with ileus Gastrointestinal: ileus that are refluxing, those that are unable to eat due to oral disease, such as a mandibular fracture, or those with dysphagia for any reason.
- By definition, parenteral nutrition is any nutrition provided through an intravenous route that is composed of one or more of the three foundations of nutrition: fat (intravenous lipid), protein (amino acids), and carbohydrate (dextrose).
Partial parenteral nutrition (PPN)
- PPN is a term most commonly used with solutions consisting of 8.5%, 10% or 15% amino acids Amino acids and 50% glucose Glucose supplemented with multivitamins Nutrition: vitamins and minerals Nutrition: minerals.
- This is physiologically more appropriate than 50% glucose Glucose alone.
- The use of 5% dextrose Glucose with water, unless used at very high infusion rates does not provide sufficient energy and once the glucose is used leaves a hypotonic fluid, which can be detrimental at a cellular level, except in particular circumstances.
Total parenteral nutrition (TPN)
- TPN refers to a combination of nutrients designed to meet the complete nutritional needs of the patient and generally refers to administration of amino acids Amino acids, 50% glucose and either 10 or 20% lipids that are supplemented with multivitamins Nutrition: vitamins and minerals Nutrition: minerals.
- Partial parenteral nutrition does not meet full nutritional requirements, and may consist of any or all parts of the TPN formulation.
- Partial parenteral nutrition is less expensive than total parenteral nutrition. Traditionally PPN is used more frequently in adult horses and TPN in neonates, however this paradigm is shifting.
- Aseptic technique must be used when compounding components of parenteral nutrition, as this product is great at providing nutrition to living organisms, whether that is a horse or a bacterium.
- Commercially available bags are marketed for this purpose. Lipids should be added after dextrose, glucose Glucose and amino acid Amino acids solutions, because dextrose solutions are acidic and can destabilize lipid emulsions when the two are mixed directly.
- Once made up they should be used within 24 h.
- As these solutions are hypertonic, they should be administered into a large diameter vein such as the jugular vein or cranial vena cava.
- The hypertonicity of the solution is reduced when given with crystalloids and these should be provided at maintenance rates or above.
- The bags should be covered with black plastic or protected from light in some way.
- Strict sepsis is also essential during administration, and dedicated lines and injection pots along with use of a double or triple lumen catheter is ideal.
- The amount to give depends on how much energy you wish to provide with your parenteral nutrition. There are various recipes that can be used varying in the proportion of calories provided by amino acids Amino acids, glucose Glucose and lipids.
- For adult horses it has been recommended that 10-20 non-protein Kcal/kg/day be administered, and for foals 40-45 Kcal/kg/day.
- It has been reported that the energy requirements for an adult horse at rest is approximately 20 Kcal/kg/day.
- As energy requirements of clinically sick horses have not been determined, and overfeeding of calories may lead to complications, the initial goal should be to provide resting energy requirements for critically ill horses. If tolerated, the caloric intake may be increased to meet maintenance requirements.
- Animals should be weaned on and off either PPN or TPN to minimize metabolic derangements.
- Usually animals are started at 50% of the target rate and then increased over 12-24 h to full rate
- Weaning is achieved by decreasing by 25% over an 8-12 h period as enteral feeding is being increased.
- PPN and TPN are used for fairly short periods of time in veterinary medicine compared with human medicine.
- There can be potentially severe problems with lack of enteral feeding for any period of time as it is associated with reduced epithelial migration and replacement and villous atrophy.
- Some supplementation, called trophic feeding is thought to improve GI function and immune status.
- When using lipid-free PPN solutions, non-protein calories are all from glucose, and 50% glucose/15% amino acid solutions may be used in a ratio of 50:50.
- When using TPN approximately 2/3 of the calories are from glucose and 33% from lipids, which is achieved by using 50% glucose, 15% amino acids and 10% lipids in a 33:33:33.
- In order to avoid hyperlipidemia, it has been suggested that 30-40% of non-protein calories should come from lipid.
- Tables to calculate amounts are available in mainstream textbooks.
- It has been shown in human medicine that patients have lower morbidity and mortality if blood glucose concentrations Blood: biochemistry - glucose are maintained between 4.2 and 6.3 mmol/L. We should aim to do this in our critically ill neonates and adults also. Some glucometers are more accurate than others and thus a compromise is to maintain blood glucose between 4 and 8 mmol/L.
- Most patients become hyperglycemic and require insulin infusions. Hypoglycemia is generally only seen when there have been rapid changes made to insulin infusion rates or animals are disconnected from their infusions.
- Blood glucose concentrations should ideally be measured frequently; approximately every 4 h until stable, then every 6-12 h.
- Catheter sites should be monitored frequently for evidence of thrombophlebitis .
- All lines should be changed every 48 h if total parenteral nutrition is used.
- These include metabolic disturbances, such as hyperglycemia Blood: biochemistry - glucose/glucosuria Urine: glucose/osmotic diuresis Polydipsia/polyuria, hyperlipidemia, hypokalemia Blood: biochemistry - potassium, hypophosphatemia Musculoskeletal: nutritional deficiencies and other electrolytes Fluid therapy: electrolyte abnormalities.
- In addition, it has been associated with catheter-related problems including thrombosis Cardiovascular: vein - thrombosis, phlebitis and sepsis. Septic complications may develop from contamination of PN bags, administration lines, or IV catheters.
- There also may be potentially severe problems with lack of enteral feeding as it is associated with reduced epithelial migration and replacement and villous atrophy.
- Parenteral nutrition is an invaluable resource in equine critical care and is easy to prepare and reasonably affordable.
- Patients unable to utilize enteral nutrition for longer than 2-3 days should have parenteral nutrition considered.
- Frequent monitoring for the development of metabolic derangements is an important component of therapy.
- Attention to aseptic technique is also critical to minimizing the development of sepsis related complications.