Critical Care Meals

Description

David F. Davenport, D.V.M., M.S. (Ag. Econ.), M.S. (Nutr.), C.N.S. Carla S. Sommardahl, D.V.M., PhD, Dipl. ACVIM J. Eric Martin, D.V.M. Introduction It is established that hypophagic or dysphagic horses can benefit from enteral nutrition.1 However, conditions such as colitis, enteritis, hepatic disease, renal disease, neoplasia and post-operative recovery require different nutritional considerations.2 Catabolic states that result from disease or surgical procedures often reduce the prognosis for recovery or unnecessarily lengthen the recovery period.3 Customized nutritional support not only provides calories in the form of carbohydrates, fats and proteins, but it can address specific nutritional needs and help alter the disease process to promote healing. Currently practitioners depend largely on ground pelleted feeds when enteral nutrition is deemed necessary. Pelleted feeds are able to provide adequate calories but fall short of providing specific nutrients that may be beneficial in certain patients. Human enteral formulas have been used with some degree of success.4 However, these diets fall short in dietary fiber, are very high in fat and due to the volume of formula used are often cost-prohibitive. Customization of the feeding program provides much more flexibility to the practitioner in terms of devising a strategic approach to feeding horses in different disease conditions. This can be achieved in a simple and cost-effective manner. The goal of this paper is to provide guidelines for the equine practitioner that will allow easy and cost-effective formulization of a component based critical care feeding program that can be customized to each horse’s individual needs. Materials 1. General Categories of Nutrients Energy: Energy in the normal healthy horse can and should be supplied to a large extent by fat.5 Fats (oils) are the densest forms of dietary energy, providing 9 calories per gram. Energy density is very important when designing an enteral nutrition program. However, in most critical care cases the energy requirements should be met primarily by carbohydrates (CHO). Even though CHO only provide 4 calories per gram, there are reasons for them to be chosen preferentially over fats. Horses that do not receive enough energy in the form of CHO will begin to catabolize muscle tissue and mobilize fat stores. This will result in a wasting syndrome clinically. Protein will be used for energy at the expense of anabolic processes. The by-products of this catabolic process (primarily urea and creatinine) place an extra workload on the liver and kidneys. This can be life threatening in many cases. Fat mobilization can result in a fatty liver syndrome in anorexic overweight equine patients, especially ponies.4 Therefore, adequate CHO intake results in the two benefits of protein sparing and decreased and decreased fat mobilization. Adequate CHO intake should be provided early in order to prevent the catabolic process and the proverbial train going down the track in the wrong direction, which becomes difficult to stop as time goes by. A dense CHO source should be provided taking into consideration the hazards associated with too much too soon (laminitis and colic). Grain diets may not provide adequate CHO due to the fact that the CHO must be extruded in the digestion process. It is the authors’ opinion that, in critically ill patients, CHO sources that require minimal processing are the most appropriate way to meet energy needs in patients that are already in a negative energy state at presentation. In horses that are not experiencing hepatic compromise, energy requirements can be addressed through the addition of vegetable fats to the enteral feeding program. Protein: When supplying protein requirements, consideration must be given to quality as well as quantity. Without high quality protein, a normally adequate quantity can still result in a horse that is protein starved.5 This will lead to continued catabolism of muscle to meet the protein needs, especially in the face of disease. High quality protein also reduces the amount of work required by the liver and kidneys, which is critical in many disease states.2 Amino acid (AA) content and digestibility of the protein determines the quality of a protein. Certain amino acids are considered rate limiting such as lysine and threonine.5 These must be supplied in the enteral diet. Other amino acids such as arginine, carnitine and glutamine contribute to glycogenisis. Arginine is also capable of accelerating wound healing and inhibiting the development of neoplasia. Carnitine, which is not an essential amino acid, stimulates protein synthesis in the face of stress and may accelerate fatty-acid oxidation, which lowers lactic acid production.5 Carnitine has also been shown to reduce hepatic fat in several species. Glutamine is a non-essential amino acid that has received attention lately in human literature. Glutamine acts as an important energy source for the enterocytes of the entire intestinal tract and renal cells. In humans it has been postulated that during periods of stress glutamine serves as the primary precursor for glutathione, a powerful antioxidant.6 It has also been suggested that glutamine shortens recovery periods in surgery and critically ill patients.7 Supplementation of the enteral feeding program with individual AA’s can be therapeutic in a wide variety of disease states. Fiber: Fiber is the hardest type of nutrient to supply a horse through a feeding tube. A reasonable goal for an enteral program is 25% of estimated need. Fiber is not soluble, so the particle size must be small enough to be suspended in the liquid meal and pass through the delivery system. As much as possible needs to be given to provide mechanical stimulation of the digestive tract. Vitamins: Vitamins are organic nutrients that are essential for normal metabolism. Well-balanced horse feeds contain enough vitamins so that frank deficiencies are not as common as in the past. However, critically ill equine patients may be in need of vitamin supplementation in order to replace depleted vitamins, overcome ingredient deficiencies, or to address increased metabolic demands. Supplemental sources should be critically evaluated for quality as well as quantity. Minerals: Though often overlooked, minerals and trace minerals are extremely important in the critically ill patient. Minerals act as cofactors for enzymes for almost every reaction in the body. Everything from immune system function, to bone density, to protein, fat and CHO metabolism is affected by mineral deficiencies. Mineral supplementation should be critically evaluated. The authors suggest amino acid chelated minerals, due to the increased bioavailability of these formulations. Other organic complexes (citrates, gluconates, and lactates) have a higher biological value than the inorganic complexes (oxides, carbonates) with sulfates being in the middle. Unless minerals are supplied in the correct balance and form, minimal benefit will be obtained by supplementation. 2. Specific Ingredients Pelleted Feeds: Pelleted commercial feeds may provide the simplest method by which to deliver some enteral nutrition. This is due to the fact that as a feed it is formulated for balance and completeness. It provides a balance of protein, CHO, some fat, vitamins, minerals as well as some fiber. Vegetable oil is often added to create a pellet-oil slurry in water that can be passed through a nasogastric (NG) tube. Pelleted feeds are nutrient dense and make meeting calculated daily needs relatively easy. Pelleted feeds must be pulverized dry in a kitchen blender and mixed with oil and water just prior to feeding. If liquid is mixed with the feed too long the cellulose will swell making administration difficult. Pelleted feeds were not designed to be soluble or suspendible and may be time consuming and frustrating. They were also balanced for the average healthy horse. A complete feed may be inadequate for the critical patient and does not allow for the customization of a component program. Liquid Preparations: Human health care products such as Ensure

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