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Chapter 22
CHAPTER 22 – NUTRITION IN METABOLIC AND RESPIRATORY STRESS
CHAPTER SUMMARY
When a person undergoes a period of severe stress from an uncontrolled infection, a wound, multiple
fractures or burns, the body attempts to sustain life with a protective stress response. The stress response
enables the body to borrow energy from one system to help keep another system functioning, at least
temporarily. Hormonal responses to stress include the use of catecholamine hormones, glucagon and
cortisol to mobilize nutrients into the bloodstream, raise heart rate and constrict blood vessels and
aldosterone and antidiuretic hormone to maintain adequate blood volume. The inflammatory response
includes the inflammatory process (swelling, redness, heat and pain), chemical substances that are
mediators of inflammation (mast cells, cytokines, eicosanoids) and the systemic effects of inflammation
including the acute-phase response (characterized by changes in plasma proteins) and possibly the
systemic inflammatory response syndrome (SIRS) or sepsis.
Metabolic stress must receive careful medical management of both the acute medical condition and the
complications of stress and inflammatory responses. The principle nutrition goals during acute stress are
to provide a diet that preserves lean tissue content, maintains immune defenses and promotes healing.
Caution is necessary to avoid overfeeding or underfeeding a patient during this critical situation. Energy
needs can be estimated using the Harris-Benedict equation, multiplied by a stress factor or by multiplying
a person’s body weight by a factor appropriate for the person’s medical condition. Protein needs are
specific to the severity of a condition, usually estimated at between 1.0-2.0 g/kg of body weight. The use
of the amino acids glutamine and arginine for wound healing and enhanced immunity is controversial.
Carbohydrates may supply up to 70% of the total calories, depending on the patient’s condition, and
lipids may supply up to 40% of total calories. Micronutrient needs in acutely stressed patients may be
increased (i.e. zinc, vitamin C, vitamin A) but specific requirements haven’t been determined yet. Enteral
feedings, parenteral feedings or a combination of both may be used to meet the nutrient needs of a
metabolically stressed patient.
Burns are the third highest cause of deaths from accidents in the United States. The classification of burns
is according to how deeply they penetrate the skin and underling tissue, while the severity of burns is
classified according to its thickness and the amount of surface area involved. Nutrition support for burns
includes intravenous fluids and electrolyte replacement for the first one to two days. The nutrition goals
for patients with burns include achieving nitrogen balance, minimizing tissue loss, promoting wound
healing and maintaining immune defenses. Nutrition support may include a diet in addition to oral
supplements and nutrient-dense snacks and possibly enteral or parenteral feedings.
Respiratory stress, inadequate gas exchange between the air and blood, resulting in lower oxygen and
higher carbon dioxide levels, due to its disruption in breathing patterns, can interfere with food intake in
some people. Dangerous outcomes of respiratory illnesses include weight loss and malnutrition. Chronic
obstructive pulmonary disease (COPD), a group of lung diseases characterized by persistent obstructed
airflow through the lungs and airways (including chronic bronchitis and emphysema), is primarily
caused by smoking tobacco, but people can be at risk due to genetic susceptibility as well. Muscle wasting
associated with COPD can be partially reversed by incorporating regular exercise. The nutrition goals for
patients with COPD include maintenance of a healthy body weight, preservation of lean muscle mass,
and improving food intake, often including the consumption of liquid nutrition supplements, although
the use of specialized low-carbohydrate formulas isn’t currently recommended.
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Chapter 22
Respiratory failure can be chronic (i.e. as a result of long-term COPD) or can occur acutely (i.e. as a result
of the depressive effects of anesthesia, an embolus, severe trauma or infection). Acute respiratory distress
syndrome (ARDS) usually resulting from an acute lung injury requires mechanical ventilation. ARDS can
lead to multiple organ failure. The nutrition goals for respiratory failure include supplying adequate
energy and protein to support lung function without overtaxing the compromised respiratory system.
Nutrition support may be needed, with preference given to intestinal feedings due to a decreased risk of
aspiration. Fluid restriction is often required, which can be accommodated with the use of nutrient-dense
formulas (i.e. 2 kcal/ml). If the risk of aspiration remains high, parenteral feedings can be implemented.
Highlight 22 discusses the development and treatment of multiple organ failure.
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