Page 427 - Small Animal Clinical Nutrition 5th Edition

Enteral-Assisted Feeding 441

components and oxygen to wound sites requires the muscular ANOREXIA, CACHEXIA AND
VetBooks.ir activities of respiration and cardiac work. Tissue trauma and Normally, satiety occurs after a patient’s caloric needs have been
ACCOMMODATION
healing alter the normal cycle of protein turnover (synthesis
and degradation) in the body. In rats, the rates of protein syn-
thesis and degradation increased after trauma (Stein et al, met. Conversely, anorexia is the loss of desire for food before
1976). Studies in perioperatively fed people indicate a 91% caloric needs have been satisfied (Box 25-1). Anorexia may be
increase in protein synthesis with only a 10% increase in pro- partial or complete. The anorexia is complete if a patient con-
tein degradation (net synthesis) (Kien et al, 1978). Con- sumes no food for a period beyond that considered normal.The
versely, perioperatively fasted people had only a 50% increase anorexia is partial if the patient consumes some food but less
in protein synthesis with a 79% increase in protein degrada- than that considered a normal daily intake.
tion (net loss) (Birkham et al, 1980). Therefore, proper nutri- The flavor of food results from chemical stimulation of taste
tion on the cellular level depends on whole body nutrition for buds and free nerve endings in the nose, mouth and throat.
net tissue synthesis and wound healing. “Taste” disorders often result from abnormalities in olfaction.
Disorders of taste or smell can impair appetite and occur
Drug Metabolism because of:
Cellular activities depend on and are regulated by the coordi- • Old age. The number of taste buds declines with age.
nated actions of peptides, lipids, vitamins and minerals as sub- Olfaction is usually the first sensory system to show an
strates, enzymes, coenzymes and cofactors of intermediary aging effect.
metabolism. Therefore, all nutrients are essential for the • Damage to neural connections due to surgery or traumatic
maintenance of normal cellular structure and function (Parke, head injury. Accidental blows to the head can shear the fine
1991). Nutrient deprivation alters the normal metabolic syn- olfactory nerves that pass through the cribriform plate and
ergy responsible for ion gradients, membrane potentials, pro- are a common cause of anosmia (inability to smell) in people.
duction of high-energy phosphate compounds and antioxi- • Impaired renewal of taste buds and olfactory epithelium.
dant defenses. Enteral and parenteral nutritional support with Decreased chemosensory cell turnover is consistent with
products containing little or no lipid decreases hepatic the decreased cell renewal reported to occur in the small
cytochrome P-450 concentration and activity, which signifi- intestinal epithelium as a result of food deprivation, radia-
cantly decreases specific drug clearances (Knodell, 1990; tion therapy, uremia, vitamin B 12 deficiency and therapy
Raftogianis et al, 1995). Protein-calorie deficiencies may with methotrexate. Many endocrine factors also depress cell
result in decreased: 1) hepatic biotransformation of certain proliferation.These factors and many conditions and drugs
antibiotics, 2) concentrations of serum proteins that bind and (Table 25-1) probably impair regeneration and function of
transport drugs throughout the body and 3) renal blood flow, taste buds and olfactory cells in the same manner that they
which decreases the rate of drug elimination and increases the impair regeneration of intestinal epithelium. The turnover
possibility of drug overdose (Walter-Sack and Klotz, 1996). time of taste buds and olfactory cells is about 10 days.
Therefore, protein-calorie malnutrition may alter the expect- Therefore, a return to normal taste function after mitosis is
ed metabolism of certain drugs, which may increase or interrupted requires at least 10 days and usually longer.
decrease their therapeutic effect even when given at recom- • Modification of receptor cells as a result of a chronic change
mended dosages (Pelissier et al, 1993; Krishnaswamy, 1989) in local environment (e.g., an alteration in saliva or the flu-
(Chapter 69). Patients receiving sufficient calories and protein ids bathing the olfactory mucosa) due to drugs or metabol-
are expected to have better, or near normal, drug distribution, ic agents such as urea.
metabolism and elimination than patients with protein-calo- Numerous medical problems including organic disease,
rie malnutrition. inflammation, trauma and neoplasia can cause anorexia. In
Inadequate nutritional support can suppress the immune addition, pain, fear and other components of emotional stress
response, cause organ dysfunction, impair wound healing, inhibit the desire for food (Schiffman, 1983). If anorexia per-
result in muscle wasting and weakness, increase the incidence sists, depletion of body nutrient stores occurs. Nutritional
of acquired infections and increase mortality. As an example, depletion may also result from facial or oral injuries, or obstruc-
a 50% decrease in jejunal mucosal mass and thickness normal- tion or dysfunction of the gastrointestinal (GI) tract, liver or
ly occurs after burn injuries when no enteral feedings are pancreas so that the patient is incapable of ingesting, chewing,
given for 24 hours. Early feeding prevents this mucosal atro- swallowing, digesting or absorbing food. In general, patients
phy. Malnutrition in people, even imprecisely defined, is asso- not eating for more than 48 hours or those consuming less than
ciated with prolonged ventilatory dependence and increased 50% of normal intake for more than three days should be of
complication rates with longer hospital stays and higher costs concern and noted as having a form of anorexia. Cats and dogs
(Remillard and Martin, 1990). Similarly in veterinary with a history of complete anorexia for three or more days or
patients, malnutrition is thought to increase morbidity and those with a history of partial anorexia for several weeks war-
mortality. Diseased and debilitated patients require nutrients rant further nutritional assessment.
daily to maintain optimal immune function, tissue synthesis Cachexia is a state of general illness, malnutrition and pro-
and repair and proper drug metabolism. found disability. For nearly 50 years, investigators and nutri-