"Nutritional Calculations" TUMOR TIDBITS, A BIWEEKLY EMAIL NEWSLETTER FROM GULF COAST VETERINARY ONCOLOGY Number 74; October 18, 2002. ======================================================================= THIS WEEK'S TUMOR TIDBIT: NUTRITIONAL CALCULATIONS ======================================================================= This is the second of a two part discussion on general considerations regarding nutrtional needs in the cancer patient. NUTRITIONAL NEEDS The patient's nutrient and water requirements should be calculated and compared with the nutrient and water intake of the animal. Nutrient intake can be estimated from the dietary history or be monitored and evaluated if the animal is hospitalized. In most cases, the animal requiring enteral nutritional support will have an intake that is less than its requirements. Calculation of the nutrient requirements of the patient requiring enteral nutritional support depends on the physiologic state of the animal. Many of these animals will be critically ill, at least initially, and may have suffered traumatic injury, sepsis, or major organ disease in combination with food deprivation. There are many conditions commonly diagnosed in veterinary medicine that increases the animal's risk of malnutrition. Disorders that may be associated with increased losses of protein and electrolytes include vomiting, draining wounds, ileus, diarrhea, abscesses, chylothorax, enteropathy/nephropathy, and malassimilation. Conditions that may be associated with increases or decreases in nutrient requirements include blood loss, liver disease, renal disease, trauma, sepsis, pulmonary disease and cancer. Nutritional support may be indicated in animals that are receiving antinutrients or catabolic drugs that result in anorexia or dysphagia. Cats have special nutritional requirements as compared to dogs because they are strict carnivores. These special dietary requirements of the cat should be considered when considering the selection of an enteral product. Cats have several special physiologic and metabolic requirements compared to dogs including a higher protein requirement; and essential need for taurine; a requirement for arachidonic acid in their diet; a higher niacin and pyridoxine requirement; and, and inability to convert B-9carotene to vitamin A. These differences become important when selecting an enteral product to feed a cat. Human liquid diets are not balanced for cats and many of the products do not contain sufficient taurine. The following steps should be used to calculate the patient's nutrient requirements (both dog and cat) and feeding level for enteral nutritional support: CALCULATE RESTING ENERGY REQUIREMENT Resting Energy Requirement (RER) Resting energy requirement is the amount of energy required by the animal in a post-absorptive resting state and accounts for a thermoneutral environment and physiological influences. In human medicine, RER is determined by indirect calorimetry but this technique is not widely used in veterinary medicine. In critically ill companion animals, the goal is to meet resting energy requirement on a daily basis. Critically ill animals will be hospitalized and confined to a cage and will have energy requirements that are below maintenance levels. Many times patients will not have eaten for several days and therefore should be adapted to the enteral diet over several days. Resting energy requirement is the starting point in meeting daily energy requirements. If the animal tolerates this level of feeding, then energy intake can be increased over time. Patients that are sent home and fed long term through feeding tubes will be fed at higher levels, closer to maintenance levels. Again, goals for energy intake will be dictated by physiological state of the animal. Many of the enteral diets that are fed to dogs and cats, the nutrient content are balanced to the caloric content of the diet. Therefore, if you feed to meet the calculated daily energy requirement of the patient all other nutrient requirements will be met. Water should be provided at the rate of 1ml for each kcal of calculated daily energy requirement. SELECT AN ENTERAL DIET Diet selection for enteral nutritional support depends on tube size and location, product availability and cost, functioning of the gastrointestinal tract, and the experience of the veterinarian. Products available to feed include blended pet foods, veterinary- formulated critical care diets, and human liquid enteral diets. Pet foods are higher in protein and fat than commercially available human liquid diets; have various nutrient profiles; are readily available; and, are the least expensive products to feed for the enteral support of dogs and cats. Both blended pet foods and veterinary-formulated critical care diet s will cause fewer complications, such as diarrhea, and usually require fewer feedings per day than human enteral diets. In most cases, a high energy and protein food should be chosen as the enteral diet. However, if the patient has renal or liver disease a veterinary therapeutic diet can be blended and fed through the tube. Patient's fed veterinary diets through the feeding tube may be fed the food directly when they have regained their appetite, thereby eliminating a diet change. The veterinary-formulated critical care diets will have increased levels of protein and fat as compared to average maintenance foods to aid in sparing lean body mass and maintain host defenses. These diets may have increased levels of branched chain amino acids, n-omega 3 fatty acids, B-9 complex vitamins, antioxidants such as vitamin E, glutamine, arginine and selected minerals (e.g., potassium, magnesium, and zinc). These diets may be formulated to be fed to both dogs and cats. These types of diets would not be indicated in animals with renal or liver disease or for animals with gastrointestinal problems that have resulted in fat intolerance. Human liquid enteral diets may cause diarrhea when fed to companion animals and the diets are usually more expensive. Furthermore, the human liquid enteral diets are not balanced for cats and must be modified with nutrient modules. Human liquid diets are available in polymeric and monomeric formulations. Monomeric or elemental diets contain nutrients in their simplest forms and require minimal digestion by the patient. Polymeric or meal replacement diets contain mixtures of proteins, fats, and carbohydrates from simple ingredients. Polymeric diets require normal digestion. Human liquid enteral diets have the advantage that they can be fed through small feeding tubes and are available in wide variety of nutrient profiles. DETERMINE FOOD DOSAGE Total food dose (mls). Daily energy requirement (kcals). Energy density of the product (kcal/ml). Initiate feeding by dividing the total daily amount to be fed by the number of feedings per day. Begin by feeding 1/3 of the food per day and gradually increase the amount of the enteral diet per day. Example feeding schedule for the first three days calculated diet + 2/3 water calculated diet + 1/3 water Full calculated diet (no water added) DETERMINE FEEDING FREQUENCY Frequency of feeding depends on the diet type, route of feeding (tube type), and digestive/absorptive capacity of the patient. For example, an animal fed through an enterostomy tube may require constant infusion of the diet. REASSESS Reassess the patient to determine response to the diet and modify the feeding plan if needed. NEXT WEEK'S TUMOR TIDBIT In next week's Tumor Tidbit, "Is chemotherapy indicated in the management of vaccine- associated sarcomas in cats?". ======================================================================= We hope this info helps and don't hesitate to call us Gulf Coast Veterinary Oncology! Kevin A. Hahn, DVM, Phd, Diplomate ACVIM (Oncology), drhahn@gcvs.com Janet K. Carreras, VMD, Residency Completed and Certification Examination Passed, ACVIM (Oncology), drcarreras@gcvs.com Glen K. King, DVM, MS, Diplomate ACVR (Radiology & Radiation Therapy), drking@gcvs.com Gulf Coast Veterinary Diagnostic Imaging & Oncology 1111 West Loop South, Suite 150, Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 W: www.gcvs.com