Incorporating enteral nutrition into your practice

Incorporating enteral nutrition into your practice

Since it's critical that ill animals receive adequate calories, if these patients aren't voluntarily consuming enough it is your responsibility to provide assistance. So read on for the why, when, what, and how of enteral nutrition.

Providing nutritional support to patients is critical because adequate caloric and nutrient intake prevents the adverse consequences of malnutrition and optimizes patient outcome. However, in a busy practice, it is easy for patients to receive suboptimal nutrition, whether because of vaguely written or absent feeding orders, anorexia, sedation from pain medications, procedures requiring the animal to be NPO, or other factors that impede adequate calorie intake.1

Inadequate intake of calories and other nutrients can be deleterious to a patient's underlying illness or injury and can negatively impact the outcome. Thus, our goals with this article are to review how to assess the nutritional needs of hospitalized animals, how to use that information to develop an individualized nutrition plan, and how to best incorporate enteral nutrition into practice.

NUTRITION IS IMPORTANT TO OUTCOME


Figure 1. Consequences of insufficient caloric intake in healthy animals compared with the consequences in ill or injured animals.
When an animal does not receive adequate calories orally to meet energy requirements, amino acids are mobilized from lean body mass to compensate for the calorie deficit. That is the body's quick solution to the calorie deficit, but it is not an efficient one since protein provides only 4 kcal/g compared with the 9 kcal/g provided from fat. Thus, within a few days, a healthy animal will make metabolic adaptations to allow fat to preferentially be used as an energy source (simple starvation), which allows for the preservation of lean body mass. Ill or injured animals are not able to make this adaptive response and continue to lose lean muscle mass (stressed starvation or cachexia; Figure 1).2

Not only is protein an inefficient source of calories, but this loss of lean body mass also has deleterious effects on the host. While carbohydrates can be stored to a small extent as glycogen in the liver and there is a near unlimited capacity to store fat in adipose tissue, the body cannot effectively store protein. Since all of the body's protein is functional, loss of lean body mass means that the animal may be losing critical functional tissue. This loss of lean body mass during illness or injury has important clinical implications. In people, lean body mass loss has been shown to impair strength, immune function, and wound healing and to reduce overall survival.3-5 And in hospitalized dogs and cats, lower energy intake has been significantly associated with reduced survival.6 Thus, it is critical to provide adequate calories, protein, and other nutrients to ill or injured animals.

NUTRITIONAL ASSESSMENT

New guidelines developed by the American Animal Hospital Association and the World Small Animal Veterinary Association stress the importance of performing a nutritional assessment of every patient at each visit.7,8 (You can find these guidelines at aahanet.org/Library/NutritionalAsmt.aspx and wsava.org/V5.htm, respectively.)

A nutritional screening includes recording a patient's body weight, body condition score (BCS), muscle condition score (MCS), complete diet history, and medical conditions as well as medications the patient is receiving. If any risk factors, such as weight loss, thin body condition, muscle loss, or underlying disease are present, a more thorough diagnostic evaluation is recommended, such as laboratory testing, diagnostic imaging, and any other pertinent diagnostic tests.

BCS primarily assesses fat stores, while MCS assesses muscle. MCS is determined by visual examination and palpation over the temporal bones, scapulae, thoracic and lumbar vertebrae, and pelvic bones. It can be described as normal or can demonstrate varying degrees of atrophy (e.g. mild, moderate, marked). BCS and MCS may not be analogous, as a thin animal may have normal muscle condition and an overweight or even obese animal may have significant muscle loss. Since animals with acute and chronic disease preferentially lose muscle (lean body mass), when caloric intake is inadequate it is critical to assess both fat and muscle stores because this information can help to identify chronic disease and may modify the nutritional plan.7,8