Preventing Malnutrition in Critical Care Patients

In human and veterinary hospital critical care settings, inadequate or excessive nutrition can impede patient recovery or compromise their conditions. For veterinary patients, studies to support the prevalence of undernutrition are limited. However, an investigation of 276 hospitalized dogs, totaling 821 dog-days, found that a positive energy balance was achieved for only 27% of dog-days and a negative energy balance remained for 73% of dog-days.¹ Critically ill patients benefit when malnutrition or risk for its development is proactively identified so that recovery can be supported. One reason why timely and adequate nutrition interventions are not performed is that the nutrition assessment/plan is an iterative and sometimes complex process, requiring additional time and, to some degree, training. In addition, the definition(s) for malnutrition are broad and may seem overwhelming when defining and identifying a patient’s level of malnutrition.

For humans, a commonly referenced definition for malnutrition is “a subacute or chronic state of nutrition in which a combination of varying degrees of overnutrition or undernutrition and inflammatory activity has led to a change in body composition and diminished function.”² The International Consensus Guideline Committee has additionally recommended using etiology-based terminology in which malnutrition is delineated as starvation-related, chronic disease–related, or acute disease– or injury-related.³ Often, within veterinary hospitals, the process of identifying and supporting patients at risk for or continuing a malnourished state is inadequate. Adopting a team approach to nutrition protocols involves delegating appropriate skills and knowledge to efficiently and effectively elevate care for critically ill hospitalized patients.

Proactive Protocols for Identifying Malnutrition or Risk for Its Development

Workflow Protocol for Nutrition Care Plan

An interprofessional approach to identify, develop, implement, and monitor a nutrition care plan suggests best practices for improving interventions to limit hospital-associated malnutrition by creating awareness and collaboration within the hospital team (FIGURE 1).

Patient Intake Protocol (Nutrition Screening)

Nutrition screening is used to identify patients already malnourished or at risk for development of malnutrition after admission to a veterinary hospital. Although the initial priority for hospitalized patients is often achieving homeostasis for their primary condition, the veterinary team should complete a nutrition screening within 24 hours of hospital admission. If the initial screening does not suggest that a patient is nutritionally at risk, screening should be repeated within 24 to 48 hours to be sure that the patient’s nutrition status has not changed.

A validated nutrition screening tool for identifying risk for malnutrition in critically ill dogs and cats has yet to be established, although general parameters have been proposed (BOX 1). The trained team member undertaking nutrition screening should be a credentialed veterinary technician or a VTS in nutrition, freeing the veterinarian to oversee completion of the nutrition screenings and confirm identification of patients nutritionally at risk that will benefit from a formal nutrition assessment.

In-Patient Protocol (Nutrition Assessment)

After the patient has been hospitalized for more than 24 hours, if the initial nutrition screening indicates any concerns for malnutrition, a full nutrition assessment should be completed every 24 hours of hospitalization after implementation of the nutrition care plan (BOX 2). The nutrition assessment does not stop after the nutrition care plan is introduced; assessment continues every 24 hours for any patient with an implemented nutrition care plan. A nutrition assessment collects additional nutrition-related factors but also indicates trends during hospitalization. Although every suggested assessment factor is used to develop the nutrition support plan, discussion of each of these points is beyond the scope of this article.

Nutrition Care Plan Protocol (Initial Nutrition Therapy)

Nutrition therapy for the critically ill patient can encompass 1 or more nutrition strategies—oral intake, enteral nutrition, and/or parenteral nutrition—as part of the medical care to support the recovery process. The strategies chosen are influenced throughout the iterative nutrition screening (within the first 24 hours of hospitalization) and assessments (every 24 hours of hospitalization thereafter). Often, the main attempt to support the nutrition of hospitalized patients focuses on improving appetite rather than ensuring adequate nutrition. The primary goal for nutrition therapy goes beyond appetite stimulation and focuses on providing adequate energy and protein, with secondary considerations for fat, carbohydrates, and micronutrients (that support immune function, wound healing, and tissue repair). Frequently, achieving these adequate nutrition targets requires supportive enteral and/or parenteral therapies as generally the targets are not achieved through appetite stimulants or oral intake alone in critically ill patients.⁴

Energy

Energy targets should be individualized for the patient’s body weight and disease-specific demands. In humans, use of indirect calorimetry (IC), when available, is the gold standard for measuring energy expenditure in hospitalized patients to account for individual variation in energy demands. The literature for humans suggests that energy intake should be initiated early and gradually, progressively reaching 100% of energy demands according to tolerance and length of time during the acute phase of critical illness.^5,6 Unfortunately, IC is not readily available for clinical use in veterinary patients and has yet to be adopted as a way to calculate energy demands for critically ill patients. Instead, calculating resting energy requirement (RER) calculations for dogs and cats are based on body weight. Underweight is indicated by a body condition score (BCS) of 1 to 3/9; ideal weight, 4 to 5/9; overweight, 6 to 7/9; and obese, 8 to 9/9. Several formulas are available, and the lead author’s clinical practice calculates RER by using the following equation with current body weight (in kg):

RER = 70 × (BW_kg ^0.75)

To avoid overfeeding obese patients, energy calculations are modified slightly. It has been suggested that for obese patients, assume that 25% of the excess weight is lean tissue and the remaining 75% is fat mass not benefiting from nutrition support.⁷ Recognizing that excess lean, metabolically active tissue requires support in the critically ill phase, accounting for that additional lean mass may support faster recovery through proteolysis inhibition (BOX 3).

In determining initial energy goals, reintroduction of energy should be slow, starting in the first 72 hours and working up to 75% of RER (e.g., day 1, 25% of RER; day 2, 50%; day 3, 75%), closely mimicking recommendations for humans.⁵ If repeated nutrition assessments identify caloric targets as insufficient, additional methods of nutrition support should be considered. After day 3 of hospitalization, consider increasing calorie targets to 80% to 100% of RER, based on patient tolerance.

Body Weight

In the critical care setting, body weight is frequently measured primarily to assess fluid status. Acute body weight changes are likely fluid related, but repeatedly low body weight may suggest inadequate calorie intake. However, body weight monitoring should not replace quantification of calorie intake as body weight may not decrease despite insufficient calorie intake.⁸ In patients in which body weight increases from edema or effusions, pairing BCS and muscle condition with body weight may help identify nutrition-associated weight gain. Fluid status and calorie intake (relative to target RER) as they relate to body weight should be assessed daily.

Protein

Critical illness is accompanied by proteolysis, which contributes to decreased lean body mass. Dietary protein can facilitate synthesis of new body protein and is essential for limiting and overcoming catabolism. When a patient’s calorie intake is deficient, a higher protein concentration in the diet is likely required to meet daily minimums, except for patients with severe renal or hepatic disease for which excess dietary protein may be contraindicated. In addition, postoperative patients or patients with major burns, sepsis, or polytrauma may require even higher levels of dietary protein. Although meeting recommended protein requirements of hospitalized veterinary patients in different disease states remains critical, limited research is available to identify variable protein targets for dogs and cats. Protein requirements should be patient specific, and calculations can be based on an ideal body weight and then compared with current protein intake (BOXES 4 AND 5). When protein intake specific to the patient cannot be calculated, an interim minimal protein concentration of 50 g/Mcal in dogs and 75 g/Mcal in cats has been recommended.¹⁰ These values are equivalent to 2 times the National Research Council (NRC)–recommended maintenance allowance of protein for adult dogs and 1.5 times the recommended maintenance allowance for adult cats.⁹

In these examples, the dog and cat are provided sufficient protein to meet recommended requirements based on NRC calculations. Should the dog or cat be receiving or consuming less than the RER, additional strategies may need to be implemented to support reaching recommended protein intake, and in some instances the protein goals may actually be based on minimal requirements instead. As a tool to continue monitoring response to protein consumption, the nutrition assessment should be reassessed every 24 hours, allowing the nutrition care plan to be promptly adjusted as needed to meet the patient’s specific needs. Whenever diet or calorie intake changes, the calculations should be repeated.

Nutrition Administration Routes

When oral intake is insufficient, likely to be delayed, or impossible, various methods can be used to support energy and nutrient intake throughout the critical care acute and recovery phases: enteral, parenteral, or both. For critically ill patients, timing and route of administration can be complex. Providing nutrition through direct enteral routes is preferred, but its initiation during the acute phase of illness can be complicated by hemodynamic instability, severe ileus, or subjective decision by the veterinarian. Although additional support from assisted feeding is beyond the scope of this article, assisted feeding should be considered early (within 72 hours of anorexia, including consideration for the time before hospitalization) when the critically ill patient is not meeting or maintaining the primary nutrition demands regarding energy, body weight, and protein.^11,12

Summary

To prevent malnutrition in critically ill patients, at a minimum a nutrition screening should be performed within 24 hours of admission. To provide nutritionally appropriate care, additional nutrition assessments should be performed daily for patients identified as nutritionally at risk, and an individual patient’s need for adjustments to the nutrition care plan should be monitored. After the patient is stabilized, priority should be given to slowly working up to 75% of ideal weight RER within the first 3 days and then 80% to 100% on day 4 and beyond (as tolerated), maintaining body weight, and providing recommended protein. The nutrition care plan for the critically ill pet is an iterative process and when monitored daily can help decrease nutrition-associated complications and elevate the level of patient care provided.