At any age or stage of life, patients with inadequate nutrient intake become malnourished. By some investigations, many hospitalized people and companion animals do not receive adequate nutrition. Ill and injured animals undergo a metabolic response that puts them at greater risk for malnutrition and its subsequent complications. Primarily as a result of alterations in cytokine levels and other hormones associated with a catabolic response to stress, these animals mobilize protein to support enhanced gluconeogesis resulting in lean body mass loss. The loss of lean body mass has a negative impact on wound healing, immune function, intermediary drug metabolism and ultimately, prognosis. However, appropriate nutritional support can minimize the loss of lean body mass and the related negative consequences. Therefore, the goals of nutritional support are to deliver adequate calories to patients that are already malnourished and to minimize the development of malnutrition in those patients that are at-risk.

In human undernourishment is also an important problem and a common cause of immunodeficiency. Approximately 40% of the individuals were already undernourished at the time they were admitted and more than 75% of the patients remained in the hospital for more than a week to recover the body weight lost. In dogs and cats, an incidence of malnutrition or undernourishment of 25% to 65% was found based on history, physiologic effects of primary disease and biochemical parameters of the animals. However, in veterinary medicine few clinical studies have been performed to determine which parameters are applicable in determining nutritional status and predicting hospital outcome. Abnormally low serum albumin, hematocrit, and hemoglobin were associated with poor clinical outcome of dogs. One study reported that half of hospitalized canine patients do not receive their daily calculated resting energy requirements, and that caloric intake may have a significant positive effect on patient outcome.

Preliminary data obtained in our Teaching Veterinary Hospital evidenced a high correlation between energy intake, body condition score and outcome. This study involved 522 dogs and cats hospitalized during the period of March 2003 to December 2005. All animals hospitalized for medical or surgical treatment of severe illness were considered for inclusion in the study. Animals hospitalized for less than 24h, with imprecise or inconclusive diagnoses, or incomplete medical histories were excluded. The following measurements were recorded for each animal: energy intake, body weight at admission and discharge, body condition score, physical status score and type of nutritional support employed. The animals had a mean energy intake of 52.7±31.5% of their calculated maintenance energy requirement (MER), and energy intake was positively associated with hospital discharge (p < 0.01). Animals that received less than 33% of their calculated MER had a discharge rate of 62.7% whereas those receiving more than 67% of their calculated MER had a discharge rate of 93.2% (p < 0.001).

Although it has been demonstrated that in some conditions with septicemia and burns there can be an increase of 25% to 35% in energy expenditure in dogs, more recent findings suggest that the energy needs at rest in dogs that are critically ill, in post-operative phase or severely traumatized are not greater than the baseline needs of healthy animals. Based on the data in the present study, patients who received 33 to 67% MER showed the same discharge rate as animals that received 100% MER. These results suggest that the administration of the resting energy requirement can be sufficient, meeting the energy demand of the majority of hospitalized patients. Outcome was dependent on body condition score (BCS) too, with discharge rates of 73% for animals with low BCS, and 84.7% for those at an ideal BCS or overweight (p < 0.01). Body nutritional reserves, such as lean body mass, appear to determine the animals' ability to overcome morbidity factors. Diseases culminate in endocrine alterations that can lead to accelerated tissue protein degradation. A hypermetabolic and catabolic state occurs as the body attempts to provide adequate amounts of glucose and amino acids for the optimization of host defenses and the repair of wounds at the site of injury, resulting in negative nitrogen balance. Therefore, in veterinary patients with poor nutritional condition, it is possible that these mechanisms of adaptation to disease are less effective. The continuous loss of lean body mass has a negative impact on wound repair, immune function, force of skeletal muscle as well as respiratory muscles, and this may explain the greater mortality found in patients with low BCS.

In conclusion, supplying calories through an adequate nutritional support to the hospitalized animal are positively associated with the rate of hospital discharge, showing it to be an important therapeutic resource.

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