3/4/2025
Critical Care
Stress
1
Introduction
• Traditional nutrition support in the critically ill population was regarded as
adjunctive care. Today we know that nutrition therapy can help attenuate the
metabolic response to stress and may reduce disease severity, decrease length
of stay in the ICU and favorably impact patient outcomes.
2
1
, 3/4/2025
Metabolic Response to Stress
Adaptive response to survive critical illness
Triggered to increase the provision of energy substrates to the vital tissues.
The pathways of energy production are altered, and alternative substrates are used as a
result
Metabolic responses to stress include:
Changes in energy expenditure
Stress hyperglycemia
Changes in body composition
The loss of muscle proteins and function is a major long-term consequence of
stress metabolism.
3
Physiological Response to Stress
Metabolic Stress Definition
• Hypermetabolic, catabolic response to acute injury or disease
• Degree of metabolic stress correlates with the seriousness of the injury
Metabolic consequences of stress result from:
• Hormone release
• Acute-phase protein synthesis
• Sustained inflammatory response
• Increased reliance on gluconeogenesis
• Shifts in fluid balance
• Decreased urine output
4
2
, 3/4/2025
Physiological Response to Starvation compared to
Metabolic Stress
• Malnutrition may develop when the body is unable to utilize nutrients or when
needs are so high that current intake cannot meet demands
• During starvation, the body responds to a reduction in food intake by reducing its
overall energy needs
Lipolysis becomes preferential means of obtaining energy and the accumulated lipid stores serve
as the primary energy source
• During metabolic stress or injury, energy requirements are increased
Glucose is used as the preferred energy source
Gluconeogenesis becomes the primary means of obtaining glucose resulting in protein
catabolism
5
Starvation vs Metabolic Stress
Metabolism Response to Starvation (Short
Term) No Injury or “Stress” (Protective • Catabolic Insult-Induced Protein-Energy Malnutrition
Adaptation Occurs) • (Protein and Energy Production Abnormal)
• Overall energy needs decrease
• Metabolic rate decreases 20−25 k cal/k • No adaptive responses activated
g/d • Increased metabolic rate 25–40 k cal/kg/d
• Energy from fat storage >90% of k cal
• Energy from protein <10% for • Increase glucose production in excess of need
gluconeogenesis
• Increase use of protein for fuel (glucose)
• Protein stores protected
6
3
Critical Care
Stress
1
Introduction
• Traditional nutrition support in the critically ill population was regarded as
adjunctive care. Today we know that nutrition therapy can help attenuate the
metabolic response to stress and may reduce disease severity, decrease length
of stay in the ICU and favorably impact patient outcomes.
2
1
, 3/4/2025
Metabolic Response to Stress
Adaptive response to survive critical illness
Triggered to increase the provision of energy substrates to the vital tissues.
The pathways of energy production are altered, and alternative substrates are used as a
result
Metabolic responses to stress include:
Changes in energy expenditure
Stress hyperglycemia
Changes in body composition
The loss of muscle proteins and function is a major long-term consequence of
stress metabolism.
3
Physiological Response to Stress
Metabolic Stress Definition
• Hypermetabolic, catabolic response to acute injury or disease
• Degree of metabolic stress correlates with the seriousness of the injury
Metabolic consequences of stress result from:
• Hormone release
• Acute-phase protein synthesis
• Sustained inflammatory response
• Increased reliance on gluconeogenesis
• Shifts in fluid balance
• Decreased urine output
4
2
, 3/4/2025
Physiological Response to Starvation compared to
Metabolic Stress
• Malnutrition may develop when the body is unable to utilize nutrients or when
needs are so high that current intake cannot meet demands
• During starvation, the body responds to a reduction in food intake by reducing its
overall energy needs
Lipolysis becomes preferential means of obtaining energy and the accumulated lipid stores serve
as the primary energy source
• During metabolic stress or injury, energy requirements are increased
Glucose is used as the preferred energy source
Gluconeogenesis becomes the primary means of obtaining glucose resulting in protein
catabolism
5
Starvation vs Metabolic Stress
Metabolism Response to Starvation (Short
Term) No Injury or “Stress” (Protective • Catabolic Insult-Induced Protein-Energy Malnutrition
Adaptation Occurs) • (Protein and Energy Production Abnormal)
• Overall energy needs decrease
• Metabolic rate decreases 20−25 k cal/k • No adaptive responses activated
g/d • Increased metabolic rate 25–40 k cal/kg/d
• Energy from fat storage >90% of k cal
• Energy from protein <10% for • Increase glucose production in excess of need
gluconeogenesis
• Increase use of protein for fuel (glucose)
• Protein stores protected
6
3
