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Veterinarian Technician March 2009 (Vol 30, No 3)

Nutrition Know-How — The Benefits of Using Nutrition in the Management of Critical Care Cases

by Ann Wortinger, BIS, LVT, VTS (ECC, SAIM, Nutrition)

    The nutritional needs of a critically ill patient can differ dramatically from those of a healthy animal. Critical patients may benefit from appropriate nutrition support during the recovery period. Insufficient nutrient intake can result in impaired immunity; decreased resistance to infection; inability to withstand shock, surgery, and the effects of drugs; decreased wound strength; muscular weakness; and organ failure. In extreme cases, insufficient nutrient intake can lead to death.1

    Indications and Goals

    The indications for initiating nutritional support include a history of illness or weight loss, a body condition score (BCS) of less than 3 of 5 or 4 of 9, acute weight loss of more than 5% of the body weight, a history of anorexia or inappetence lasting more than 3 days, the presence of injuries that could prevent adequate oral intake, or the inability to protect the airway.2

    Nutritional goals for critical care patients include meeting their special nutritional needs and preventing further deterioration associated with nutritional inadequacy. These goals can be accomplished by providing protein, carbohydrate, fat, and other nutrients in a formula that the body uses with maximum efficiency and minimal adversity and without causing discomfort if the nutrients need to be delivered by tube.3

    When the body uses exogenous nutrients, which are provided by sources outside the body, rather than endogenous nutrients, which are provided by the body's own stores, the breakdown of lean body mass is slowed and the patient's response to therapy is optimized.4 Increased protein breakdown in response to illness or injury can deplete the body of protein stores, thereby affecting wound healing, immune and cellular functions, and cardiac and respiratory functions.5

    The cornerstones of nutritional assessment are conducting a complete physical examination, obtaining a detailed patient history, recording body weight, assessing the patient's body condition, and evaluating blood chemistry profiles.4 The patient's condition will determine which blood profiles are required.

    The BCS, however, may not always provide an accurate picture of available energy reserves for critically ill animals. When an animal is physiologically stressed, lean body mass is its preferred energy source; in contrast, healthy animals use stored body fat for energy. When the body uses lean body mass for energy, the result is increased catabolism of body protein in the form of the animal's own muscle and organ tissue.1

    A patient may present with increased amounts of body fat but be at serious risk for malnutrition-associated complications caused by protein catabolism. Careful examination, including palpation of skeletal muscles over bony prominences (e.g., the scapula, vertebrae, hips, and cranial crest), can help identify any muscle wasting consistent with increased protein catabolism.2

    Caloric requirements are determined by body weight and function and can be calculated by using the resting energy requirement (RER) for healthy adult animals at rest in environmentally comfortable cages.3 The application of illness factors to the RER is now believed to be a source of complications rather than a way to improve the clinical outcome and is, therefore, discouraged.4 Patients that eat more than the calculated RER amounts should not be discouraged from doing so while recovering from surgery or trauma.

    As the animal recovers and its activity increases, the maintenance energy requirement (MER) can be used to calculate caloric needs. The MER depends on the activity level and environment of the patient and can range from 1.0 for a very inactive house dog to 2.0 for an active hunting or agility dog housed outdoors. The most important consideration is that the animal be able to maintain a BCS of 3 of 5 or 4 of 9 on the amount of food being fed.

    The gut is generally the safest and most natural route for administering nutrients. Maintaining the intestinal mucosa may help prevent bacterial translocation from the gut to the rest of the body and is best accomplished with enteral feeding.6 Voluntary oral intake is the preferred enteral route of feeding, but patients must be able to consume at least 85% of the calculated RER for enteral feeding to be effective.5,7 If a patient is unwilling or unable to eat voluntarily, tube feeding should be considered, although it is limited by diet selections. In most instances, only liquid or gruel diets can be fed through a tube because of its small internal diameter. In addition, tubes can become clogged and must be flushed with water frequently.3

    Calorically dense, highly palatable diets with high levels of protein, moderate to high fat content, and low levels of carbohydrate provide excellent nutritional support in the management of critically ill patients.8 Therefore, protein and fat can be important sources of energy,8 and diets high in protein, moderate in fat, and low in carbohydrate are usually appropriate in these cases. Before evaluating the need for fat, protein, and carbohydrate, however, a good diet strategy should address the animal's requirement for water and correct any preexisting fluid and acid-base deficits.8 After these needs have been satisfied, sufficient fat, carbohydrate, and protein should be provided to meet the animal's energy requirements and minimize the gluconeogenesis of amino acids.8

    Commercial pet foods are designed to meet the dietary requirements of cats and dogs and contain ingredients (e.g., glutamine, taurine, l-carnitine) not usually found in liquid or parenteral diets.8 The principal differences between human and animal liquid diets are the protein content and the extent that ingredients are subject to hydrolysis.8 For example, most human enteral diets contain 14% to 17% protein, which is insufficient for both dogs and cats, and arginine and methionine levels in human enteral diets tend to be too low, especially for cats.8 Pediatric or growth pet diets are often recommended because they are highly digestible and high in fat and protein and are considered palatable.9 Meat-based baby foods contain 30% to 70% protein and 20% to 60% fat. However, because they are deficient in calcium, vitamin A, and thiamine, baby foods should not be used as the sole dietary source for animals.6

    The Role of Technicians

    Technicians responsible for providing nutritional support to critical patients should be given clear instructions on the type of food to be offered, the amount to be given, and the frequency of administration. One study showed that in 22% of cases, inadequate nutritional support was the result of poorly written orders from the clinician, who is responsible for ensuring that the amount to be fed has been calculated accurately and that the instructions are clear and concise.4

    A chart can be used to record the amount eaten, the technique used to feed the patient, and the food that was offered (e.g., ½ can of slightly warmed dog food offered by hand at 3:00 pm; ate well). The technician can then draw a circle on the chart and fill in the amount of food the patient consumed (e.g., filling in one-quarter of the circle if the patient ate one-quarter of the amount offered); if the patient refused to eat, an "R" can be placed within the circle. The technician also should note whether the food, the amount, or the feeding technique differed from the instructions. Precise record keeping provides veterinarians with an accurate measurement of food intake and technicians with a history of feeding methods that succeeded on a per-patient basis, which can be especially helpful during shift changes.

    Diet transitions may occur while the patient is hospitalized, although this typically takes place 2 to 6 weeks after the patient has been discharged. Transition depends on the diet being fed, the condition of the patient, the patient's response to therapy, and the comfort level of the owner. As with diet initiation, it is best to proceed slowly. When shifting the dog from a support diet to a maintenance diet, the maintenance diet may be increased by one-quarter increments every 3 to 4 days. For example, on days 1 to 4, three-quarters of the therapeutic diet and one-quarter of the maintenance diet should be fed; on days 5 to 8, one-half of the therapeutic diet and one-half of the maintenance diet should be fed; on days 9 to 12, one-quarter of the therapeutic diet and three-quarters of the maintenance diet should be fed; and on day 13, 100% maintenance diet should be fed (i.e., following the recommended transition phase of 12 to 16 days). If a problem develops at any stage, the owner should be instructed to return to the last diet combination that worked.

    Technicians should supply owners with well-written, concise discharge instructions as stipulated by the veterinarian, along with reasonable expectations of what the recommended diet can do.

    Being aware of the nutritional needs in critical care patients can aid in their recovery and improve their prognosis, as well as the client-patient-veterinary team relationship. Technicians can assume a primary role in providing excellent nutrition support.

    1. Buffington CA, Holloway C, Abood SK. Clinical dietetics. In: Manual of Veterinary Dietetics. St. Louis, Mo.: Elsevier; 2004:54-60.

    2. Elliot DA. Parenteral nutrition. Proceedings of the 29th World Congress of the World Small Animal Association. Rhodes, Greece: October 6-9, 2004.

    3. Remillard R, Armstrong PJ, Davenport D. Assisted feeding in hospitalized patients: enteral and parenteral nutrition. In: Hand M, Hatcher C, Remillard R, Roudebush P (eds). Small Animal Clinical Nutrition, ed 4. Marceline, Mo.: Walsworth Publishing; 2000:352-370.

    4. Chan DL. In-hospital starvation: inadequate nutritional support. Proceedings of the 11th International Veterinary Emergency & Critical Care Symposium. Atlanta, Ga.: September 6-11, 2005.

    5. Torrance AG. Intensive care nutritional support. In: Manual of Companion Animal Nutrition and Feeding. Ames, Iowa: Iowa State University Press; 1996:171-180.

    6. Wingfield WE. The essentials of life in critically ill animals. In: Purina Nutrition Forum. St. Louis, Mo.: Ralston Purina; 1997.

    7. Donaghue S. Nutritional support of hospitalized patients. Vet Clin North Am Small Anim Pract 1989;19(3):475-493.

    8. Tennant B. Feeding the sick animal. In: Manual of Companion Animal Nutrition and Feeding. Ames, Iowa: Iowa State University Press; 1996:181-190.

    9. Hill RC. Critical care nutrition. In: Wills JM, Simpson KW (eds). The Waltham Book of Clinical Nutrition of the Dog and Cat. Tarrytown, N.Y.: Pergamon Press; 1994:39-57.

    References »

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