Author: Christal Pollock, DVM, Dipl. ABVP-Avian
Date: Originally written 9/97; revised November 10, 2007
Keywords: Nutrition, parenteral nutrition, TPN, starvation, malnutrition, protein, enteral feeding, critical care, hypermetabolism.
Key Points
- Metabolism slows during starvation and increases during critically illness.
- Nutritional support is indicated in the patient with significant weight loss, extended anorexia, and/or a low serum albumin.
- Tube feeding is the preferred method of nutritional support.
- Parenteral nutrition is indicated if the bird cannot be tube fed or cannot protect its respiratory tract.
- Parenteral nutrition solution is a mixture of protein, carbohydrate, and lipid.
- Follow strict aseptic technique when compounding and administering parenteral nutrition.
- Potential complications which can develop include hyperglycemia, glucosuria, hypophosphatemia, and sepsis.
Important concepts in parenteral nutrition
Energy reserves
While mammals utilize carbohydrate as an immediate energy source, birds utilize fat. The ability of birds to store triglycerides for energy is far greater than in any other vertebrate.
Starvation
Starvation is associated with a gradual decrease in metabolic rate. Initially, energy needs are met by oxidation of fat, however the longer starvation lasts the more protein is catabolized. Amino acids are utilized for gluconeogenesis or reassembled to support vital organs. Fortunately, consumption of even small amounts of carbohydrate has a sparing effect on protein.
Hypermetabolism
Metabolic stressors such as sepsis, trauma, severe illness, and surgery lead to an increased demand for nutrients or hypermetabolism. When this increase in metabolism is paired with anorexia or malabsorption, body proteins are catabolized for gluconeogenesis. Carbohydrates have little, if any, sparing effect on body protein in mammals. In fact, glucose administration may increase metabolism further.
A patient receiving inadequate protein and calories is at increased risk for infection, delayed healing, and dehiscence.
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Assessment of nutritional status
Obtain a dietary and clinical history, and assess body condition score. Even obese animals can be malnourished and should be carefully palpated for reduced muscle mass.
Albumin is the best indicator of long-term malnutrition, however levels change slowly so albumin is a poor indicator of early undernourishment. Of course albumin levels can be altered by hemorrhage, dehydration, and liver disease.
Malnutrition also alters cell-mediated and humoral immunity. Lymphocyte counts less than 800/ml have been shown to empirically correlate with severe immunodeficiency in humans, dogs, and cats.
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Nutritional support
The goals of nutritional support are to halt protein catabolism and promote protein synthesis. Indications for nutritional support include:
- Total or partial anorexia. Significance of the duration of anorexia varies with the size of the bird. A 3-hour fast can have significant metabolic effects in the tiny yellow bunting (Emberiza sulphurata), while considerable changes are not seen for at least 24 hours in domestic fowl or pigeons (Columba livia).
- Weight loss of 5-10% body weight
- Hypoalbuminemia, hypoproteinemia
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Parenteral nutrition
If the gut works, use it. The preferred route for providing nutrition is enteral feeding since this preserves intestinal structure and function.
Parenteral nutrition is indicated to prevent malnutrition when patients cannot consume adequate nutrients by oral feeding or tube feeding or when the respiratory tract cannot be protected. Parenteral nutrition is 100% bioavailable since nutrients reach tissue without the variations associated with gastrointestinal digestion.
Energy requirements
Calculate energy and protein requirements (see TPN worksheet). Calories provided by protein may be added to recovery energy requirements (RER). If the volume needed is too large to be realistically administered or if the patient suffers from renal or hepatic disease, then subtract calories provided by protein from total calories needed.
Dextrose and lipid are usually provided in a 50:50 or 40:60 ratio. Theoretically, the amount of lipid in avian parenteral solution could be increased since granivorous birds are able to utilize a higher amount of dietary fat.
Parenteral nutrition usually provides more than maintenance fluid requirements, however supplemental fluids may be indicated if losses continue due to vomiting or regurgitation, diarrhea, exudation, or diuresis.
Vascular access
The catheter used for TPN must be a dedicated intravenous (IV) or intraosseous line. It cannot be used for blood sampling or drug administration. To provide TPN through an IV catheter a central vein must be used because of the solution’s hyperosmolality (see partial parenteral nutrition).
Compounding
Parenteral nutrition solutions consist of:
- Amino acid solution containing all essential amino acids except taurine.
- Lipid emulsion providing essential fatty acids. (Do not give lipids to patients with lipemia or severe liver disease).
- 50% Dextrose
- Electrolytes
- Trace elements
- Vitamins: Available products lack vitamin K (supplement vitamin K at 0.5 mg/kg subcutaneously on Day 1 then once weekly)
Prepare solution under strict aseptic conditions. Ideally TPN is mixed in a laminar flow hood, however a surgery room is a practical alternative.
“All in one” or “3-in-1” is the most convenient and economical form of TPN.
- Combine solutions in a sterile container, preferably made of ethylene vinyl acetate.
- Never mix lipid and dextrose directly. First add lipid, then amino acids, and finally dextrose. Ingredients may also be added in the opposite order.
- Swab injection ports with 70% isopropyl alcohol.
- Never inject air into vials to facilitate withdrawal of contents.
Administration
The infusion rate should meet basal energy requirements (BER) on Day 1. Beginning on Day 2, gradually increase the rate to recovery energy requirements (RER) over 24-48 hours.
Constant rate infusion (CRI) is most commonly used to administer TPN solution. However if the patient is to be nourished by TPN for an extended period of time, cyclic feeding may be indicated. In cyclic feeding, solutions are infused for 12-18 hours and then administration is tapered off. In human patients, solution is infused at night and halted during the day to give the patient freedom form machinery. Cyclic feeding may also minimize the adverse effects associated with CRI in patients accustomed to meals and an overnight fast. Therefore granivorous birds that eat lots of little meals during the day may benefit most from CRI, while large parrots on twice-daily meals or large carnivorous species may benefit from cyclic feeding or multiple boluses throughout the day.
Aseptically change the bandage and fluid administration set every 24-96 hours. Change the catheter only when necessary.
Potential complications
A variety of mechanical and metabolic complications have been reported in humans and small animals on TPN:
- Hyperglycemia and glucosuria
- Severe hyperphosphatemia and subsequent weakness and tremors can occur within the first 24 hours of TPN without supplementation.
- Moderate lipemia is common for 1 to 2 days after TPN is started.
- Nearly all humans show prerenal azotemia, however uricacidemia was not observed in pigeons given TPN.
- “Refeeding syndrome” is most likely to occur in the severely malnourished secondary to rapid changes in fluid, electrolytes, and glucose tolerance. Rapid changes lead to fluid retention and ensuing congestive heart failure and/or pulmonary edema.
- Although catheter-related complications are relatively rare, potential problems include thrombophlebitis, edema, cellulitis, thromboembolism, and/or sepsis. The incidence of sepsis in humans is 3-5% when aseptic technique is followed, however the infection rate can increase by 33% if aseptic technique is not followed.
Monitoring
- Weigh patients once or twice daily
- Assess blood and urine glucose regularly
- Evaluate electrolytes 1-2 days after starting TPN, then twice weekly if body size allows.
- Avian patients rarely receive TPN for extended periods, however evaluate biochemistry panel and complete blood count at least weekly in these individuals.
Discontinuation
Offer food as small, frequent meals, and discontinue TPN when oral intake provides more than 50% of RER.
Gradually decrease the infusion rate over several hours to taper dextrose levels. Suddenly halting dextrose infusion, even for 15-30 minutes, is associated with a rapid fall in insulin levels. If infusion must be stopped abruptly, as in the case of sepsis, infuse 5% dextrose drip in 0.45% saline with potassium chloride supplementation at the same rate for 6-8 hours.
Tapering is not as important if the bird is eating well. Stop infusion after a meal to avoid hypoglycemia.
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Partial parenteral nutrition
Nutrition administered through a peripheral vein is almost always partial parenteral nutrition (PPN) due to volume and osmolarity constraints. The exception to this rule is lipid. Due to their isotonic nature, lipid emulsions can be completely absorbed when given peripherally. Since PPN only partially meets energy requirements, protein breakdown will exceeds synthesis if some food is not provided by mouth.
PPN is indicated if:
- some food may be given by mouth
- the period of fasting is expected to be relatively short
- central venous catheter placement is not possible or too risky
Change peripheral catheters every 72 hours. To minimize the risk of phlebitis, select the largest vein possible and place the smallest catheter possible. Maintain osmolarity less than 1000 mOsm.
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References
Degernes LA, Davidson GS, Kolmstetter C, Munger L. Administration of total parenteral nutrition in pigeons. Am J Vet Res 55(5): 660-665, 1994.
Forbes A. Parenteral nutrition. Curr Opin Gastroenterol 22(2):160-164, 2006.
Griminger P. Lipid metabolism. In: Sturkie PD (ed). Avian Physiology. New York, NY: Springer-Verlag, 345-358 (1986).
Hwang TL, Lue MC, Chen LL. Early use of cyclic TPN prevents further deterioration of liver functions for the TPN patients with impaired liver function. Hepatogastroenterology 47(35):1347-1350, 2000.
Janssen DL, Oosterhuis JE, Allen JL, et al. Lead poisoning in the free-ranging California condors. J Am Vet Med Assoc 189(9):1115-1117, 1986.
Jenkins JR. Hospital techniques and supportive care. In: Altman RB, Clubb SL, Dorrestein K, Quesenberry K (eds). Avian Medicine and Surgery. Philadelphia, PA. WB Saunders. 1997:246-248.
Kansas State University College of Veterinary Medicine. TPN Worksheet. 2007.
Meguid MM. Past, present, and future of nutritional support. Nutrition 10(5 Suppl): 514-156, 1994.
Heiss C, Houghton M. Parenteral Nutrition Tutorial: Continuous vs. cyclic. 2000. Available at: http://www.csun.edu/~cjh78264/parenteral/initiation/initiation02.html. Accessed November 10, 2007.
Pollock C. Practical parenteral nutrition. Proceedings of the Annual Conference Association of Avian Veterinarians; 1997. pp. 263-276.
Pyle SC, Marks SL, Kass PH. Evaluation of complications and prognostic factors associated with administration of total parenteral nutrition in cats: 75 cases (1994-2001). J Am Vet Med Assoc 225(2):242-250, 2004.
Scolapio JS. A reviw of the trends in the use of enteral and parenteral nutrition support. J Clin Gastroenterol 38(5): 403-407, 2004.
Tarachai P, Yamauchi K. Effects of luminal nutrient absorption, intraluminal physical stimulation, and intravenous parenteral alimentation on the recovery responses of duodenal villus morphology following feed withdrawal in chickens. Poult Sci 79(11):1578-1585, 2000.
University of Tennessee College of Veterinary Medicine. TPN Worksheet. 1996.
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TPN Worksheet
a Do not administer Liposyn to lipemic birds or those with severe liver disease.
b Use half this amount of dextrose on Day 1 and increase to full amount of Day 2 if there are not problems with glucosuria.
c Some amino acid solutions contain electrolytes. |
| 1. Basal energy requirements (BER) |
BER = K (Wkg)0.75 = kcal/day
K = 78 for non-passerines
K = 129 for passerines |
2. Recovery energy req (RER)
RER = _____ x BER = _____ kcal/day |
Cage rest = 1.25 x BER
Post-op = 1.25-1.35 x BER
Trauma = 1.35-1.5 x BER
Neoplasia = 1.35-1.5 x BER
Sepsis = 1.5-1.7 x BER |
| 3. Calculate protein requirements |
| 6 g/kg has been used in birds |
| 4 g/kg in adult dogs |
6 g/kg in adult cats |
| 6 g/kg in dogs w/ excessive protein loss |
| 1.5 g/kg in dogs with kidney or liver failure |
3.5 g/kg in cats with kidney or liver failure |
| 0.8 g/kg in healthy adult humans |
| 1.5-2.0 g/kg in hypermetabolic humans |
| Protein needs correlate with BER in children with protein calories making up a 7-10% of total caloric intake |
Children < 2y 2.0-2.5 g/kg
Human children 2-10y 1.5-2.0 g/kg
Children > 10y 1.0-1.5 g/kg |
| Grams of protein required = _______ |
| 8.5% Amino acid solution = 0.085 g protein/ml |
_____ g protein x 1 ml/0.085 = _____ ml Aminosyn® |
| 4. The calories provided by protein are: (a) added to RER needs OR (b) protein calories are subtracted from total calories in patients with hepatic or renal disease or if the total volume is to large to be realistically administered |
| Protein calories + RER in lipid and carbohydrate |
Non-protein calories = RER –(_____ kcal of protein) |
| 20% lipid solution = 2 kcal/ml |
| Supply 50-60% of calories as lipid. |
| 0.5-0.6 x RER = _____ kcal |
0.5-0.6 x non-protein calories |
| _____ kcal x 1 ml/2 kcal = _____ ml Liposyn® a |
| 50% dextrose solution = 1.7 kcal/ml |
| Supply 40-50% of calories as carbohydrate |
| 0.4-0.5 x RER = _____ kcal |
0.4-0.5 x non-protein calories = _____ kcal |
| _____ kcal x 1 ml/1.7 kcal = _____ml 50% dextroseb |
| 5. Electrolyte requirements |
| Add 20 ml TPN electrolytes and 5 ml potassium phosphate to each liter of solution if electrolyte levels are normal. The resulting solution contains: |
| Sodium 35 mEq/L |
Chloride 35 mEq/L |
| Potassium 42 mEq/L |
Phosphorus 15 mmol/L |
| Calcium 4 mEq/L |
Magnesium 5 mEq/L |
| If the patient is hypokalemic, further supplementation with potassium chloride is needed to achieve the total potassium level desired. |
| 6. Vitamin requirements |
| Available products lack vitamin K. Give 0.5 mg/kg vitamin K subcutaneously on Day 1 and then once weekly. |
| 7. Fluid requirements |
| Parenteral nutrition usually provides more than maintenance fluid requirements, however supplemental fluids may be indicated if losses continue due to vomiting or regurgitation, diarrhea, exudation, or diuresis. If additional fluid therapy is needed, crystalloids may be added to the TPN bag or may be given by a separate catheter. |
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Sample Calculations
|
Example: 3-month old Blue and Gold macaw () with chronic regurgitation and weight loss. Based on lab results, a hepatic component to this disease is suspected. Body weight is 0.7 kg.
|
| 1. Basal energy requirements (BER) |
BER = K (Wkg)0.75 = kcal/day
K = 78 for non-passerines
K = 78 (0.70)0.75
K = 78 x 0.765
K = 59.69 kcal/day |
| 2. Recovery energy req (RER) |
RER = 1.5 x BER = 89.5 kcal/day |
| 3. Protein requirements |
Protein = 4 kcal/g |
| 6 g protein/kg |
6 g protein x 0.7 kg = 4.2 g protein |
| 8.5% Amino acid solution = 0.085 g protein/ml |
4.2 g protein x 1 ml/0.085 g = 49.41 ml Aminosyn |
| 8.5 Amino acid solution = 0.34 kcal/ml |
49.41 ml x 0.34 kcal/ml = 16.79 kcal |
| 4. Since liver disease is suspected, calories provided by protein are subtracted from the total calories needed. |
| Non-protein calories = RER –protein calories |
89.5 kcal – 16.79 kcal = 72.7 kcal |
| Supply 60% of non-protein calories as lipid. |
0.6 x non-protein calories = 43.62 kcal |
| 20% lipid solution = 2 kcal/ml |
43.62 kcal x 1 ml/2 kcal = 21.81 ml Liposyn |
| Supply 40% as carbohydrate |
0.4 x non-protein calories = 29.08 kcal |
| 50% dextrose solution = 1.7 kcal/ml |
29.08 kcal x 1 ml/1.7 kcal = 17.1 ml 50% dextrose |
| Use half this amount on dextrose on Day 1 |
The bird would receive 79.1 ml of 3-in-1 TPN on Day 1, then 88.3 ml on Day 2
3 ml/hour on Day 1, then 4 ml/h on Day 2 |
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Price List for TPN Solutions
| Product |
Quantity |
Cost |
* Aminosyn II with Electrolytes is commercially available.
** Syringes can be used instead of bags. |
Aminosyn II®*
Abbott Laboratories |
1 L |
22.68 |
Liposyn®
Abbott Laboratories |
500 ml |
37.56 |
| 50% Dextrose |
50 ml |
0.78 |
| Sterile empty bag* |
250 ml |
2.05 |
TPN electrolytes
Abbott Laboratories |
20 ml |
9.25 |
Multivitamin injection
Astra-Zeneca |
10 ml |
13.80 |
| Potassium phosphate |
15 ml |
2.20 |
