The critical role of nutrition for hospitalized veterinary patients
As we continue to learn the importance of nutrition for a patient's long-term health, veterinary technicians must equip themselves with the knowledge to serve the nutritional needs of their patients. This entails, in part, knowing how to properly assess hospitalized patients for signs of existing malnutrition and being able to intervene before malnutrition develops. Let's explore how to assess the need for nutritional support and create a plan to support and speed the patient's recovery.
Stressed vs. unstressed starvation
Simply put, any fasting animal will adapt by altering its metabolism. These alterations preserve energy reserves and conserve endogenous protein. Carbohydrates, fats, and proteins can all be used as sources of energy. But the metabolism of a healthy fasting animal is very different than the metabolism of an injured or ill fasting animal. A healthy animal will first use carbohydrates and fat stores as fuel. In critically ill or injured animals, protein catabolism is actually accelerated (also known as a hypermetabolic response to injury). When 25 percent to 30 percent of body protein is consumed, cardiac failure, respiratory failure, or infections secondary to immunosuppression can lead to death.Patients with a history of anorexia or prolonged periods of decreased appetite, nausea, vomiting, regurgitation, or diarrhea are at risk for malnutrition because their nutritional intake is less than optimal. Nutrient digestion and absorption will lead to protein loss if a patient experiences vomiting, regurgitation, or diarrhea. The body has no storage form of protein. All endogenous proteins serve some functional purpose, such as structural proteins, enzymes, and carrier proteins.
A healthy fasting animal will make metabolic adaptations over the course of days or even weeks. These adaptations are aimed at decreasing demands for glucose to fuel tissues that use it either exclusively or preferentially for energy production. Some tissues of the body can only use glucose as fuel. The glucose reserves are used up in the first 24 to 72 hours of a fast. Some tissues can use fat as fuel. Other tissues use glucose but will then switch over to other fuel sources, such as ketone bodies (keto-adapt).
A critically ill animal cannot keto-adapt. Therefore, when the body starts breaking down endogenous protein for energy, it is really the animal's muscle and eventually its organs that are compromised. In a fasting, critically ill patient, it is the lack of amino acids rather than the lack of calories that is likely to be life-threatening.