Page 437 - Small Animal Clinical Nutrition 5th Edition

Enteral-Assisted Feeding 451

and then subsides by Days 7 to 10 unless complicated by sepsis caloric intake is to be supplied by protein, then that fraction of
VetBooks.ir (Moore and Moore, 1994). Energy expenditure of people with protein intake that is used for energy vs. that which is used for
protein synthesis must be estimated because the same amino
other disease conditions probably follows a similar pattern with
acid cannot do both.Theoretically, if protein were supplied at 4
varying requirements above RER that may occur over time.
Hospitalized veterinary patients are assumed to be similar to g/100 kcal to the patient but all of it was oxidized for energy
ill people and their DER is very near their RER. Results of a with none going to synthesis, the protein could only account for
few preliminary respiration calorimetry measurements in dogs 14% (4 g x 3.5 kcal/g) of the total caloric intake at best.
with specific disease conditions suggested that most had The most conservative and simplest method is to first pro-
requirements near RER (Walton et al, 1996; Ogilvie et al, vide the entire caloric need with fat and carbohydrate, and then
1996). Estimating the RER of hospitalized patients should be meet the protein requirement entirely with amino acids, and
calculated by the equation RER = 70(BW ) 0.75 (Chapter 5). not estimate the fraction of the protein that may be catabolized
kg
Most hospitalized veterinary patients should be fed at their cal- vs. anabolized. This method will not shortchange either the
culated RER, realizing their actual energy requirement is likely caloric or protein requirement because the fraction of amino
to change over the course of the disease process and recovery. In acids actually used for energy will provide only a small amount
human surgical patients, there was relatively little additional (<15%) of additional calories. Essential amino acids provided
benefit to increasing intake after half of the caloric requirement by food are most efficiently used in protein synthesis and
of patients had been achieved (Elwyn et al, 1981). Therefore, should not be used for energy, if at all possible. In summary,
initially feeding patients at RER, or at least 60% of RER, if protein calories may be taken into account, however, the con-
100% RER is not possible, is a rational and safe recommenda- tribution is small and not significant.
tion that decreases the probability of metabolic complications.
Regular nutritional assessment of the patient is strongly recom- Carbohydrate
mended to adjust initial feeding rates. Carbohydrate usage during the healthy fed state results in ener-
There are exceptions when the caloric requirement will be gy storage (glycogen) or energy production (ATP) in a very
greater than RER. Particular cases have energy requirements efficient manner. Conversely, use of this nutrient in refeeding
1.3 to 2.1 x RER as determined by bedside respiration calori- scenarios during the unfed state is less efficient and can result
metry in people (Moore and Moore, 1994). For example, in adverse metabolic and physiologic states, particularly in dis-
according to indirect respiration calorimetry, people with severe eased or injured patients. Insulin resistance, presence of bacte-
closed-head and brain injury have energy requirements 40 to ria with infection, diminished production of digestive enzymes,
60% above their calculated RER (Ott et al, 1990). Brain injury altered GI absorptive capacity and alteration of gut microbiota
apparently increases oxygen consumption and acute-phase pro- complicate the recovery process and influence dietary carbohy-
tein synthesis, which subsequently increase patients’ caloric and drate tolerance. The two major clinical manifestations current-
protein requirements significantly above RER. Energy require- ly associated with carbohydrate intake include altered glucose
ments of twice RER appear to be the upper limit in the most control and diarrhea. Consequently, most foods formulated for
severe head injuries. Energy expenditure may be 30 to 50% recovery are low in carbohydrate content.
above RER in patients with multisystem trauma. Severely Tight glucose control in ICU patients has been regarded as
burned patients also have energy and protein requirements 80 beneficial because both hyperglycemia and hypoglycemia have
to 100% above RER, relative to the extent of skin damage and detrimental effects on tissue function and clinical outcome, but
surface area exposed (Moore and Moore, 1994).The body loses recently this goal has been challenged (Elia and De Silva,
heat, moisture and protein through wounds that have little or 2008). Adverse effects of hyperglycemia that can predispose the
no epithelial covering. The patient’s actual metabolic rate and patient to infection and delay recovery from illness include
resultant energy requirement are related to the degree of trau- osmotic shifts, glucosuria, altered immune and endothelial cell
ma, disease and/or complications and can only be approximat- function and promotion of free radicals. Conversely, hyper-
ed in a clinical setting. glycemia is a normal response to injury or stress. Glucose is
The energy density of foods intended for patients requiring needed for wound healing and inflammatory/immune cells that
assisted feeding is often reported relative to the water or fluid are involved in the metabolic response to injury, as well as other
content of the food. This is because an animal’s energy require- physiologic functions. A review of several human ICU-based
ment in kcal is approximately equal to its water requirement in studies indicated that narrowly controlled glucose did not sig-
ml and most critical care feeding is done in a liquid form. Thus, nificantly reduce hospital mortality (Elia and DeSilva, 2008).
when patients are fed a sufficient amount of food to meet their Circulating glucose is the major energy source for the brain.
energy requirements,they also meet their requirements for water. Although in most ICU patients, during the unfed state and
The recommended energy density of a food intended for assist- during diabetic ketoacidosis, the brain can use ketones as an
ed feeding (enteral or parenteral nutrition) is 1 to 2 kcal/ml. energy source. Once re-fed, the circulating insulin acts to sup-
press ketone body concentrations, which once again leaves glu-
Adjusting for Protein Calories cose as the major energy source for the brain. Reducing the
Calculating and adjusting for protein calories is of minor con- blood glucose concentration in some patients (lower than seen
sequence when feeding at RER. If one assumes that part of the with stress/injury response) could have detrimental effects such