Nutrition and Intensive Care

Question 1

explain the role of cytokines

Answer 1

• cytokines: interleukins, tumor necrosis factor (TNF), eicosanoids (PGE2) are released by phagocytes in response to tissue damage, infxn, inflammation
  
  • have a local (paracrine) effect as well as systemic

Question 2

describe local effects of cytokines

Answer 2

• promote wound healing by ingrowth of fibroblasts
• stimulate angiogenesis
• increase white cell counts and facilitate white cell migration
• localize the wound

Question 3

describe system effects of cytokines

Answer 3

• mobilization of amino acids, stimulation of acute phase protein synthesis by liver
• fever (increase metabolic rate)
• pain

Question 4

name the most important mediator of inflammation

Answer 4

phospholipid -> arachidonic acid -> PGE2 (prostaglandin)

Question 5

contrast the ebb phase and the flow phase

Answer 5

Question 6

describe the ebb phase

Answer 6

• immediate response following an injury: hypovolemia, shock, tissue hypoxia
• decreased cardiac output
• decreased O2 consumption (decreased metabolic rate)
• lowered body temp.
• insulin levels drop and glucagon and epi. are elevated

Question 7

describe the changes in carbohydrate metabolism during the ebb phase

Answer 7

• elevated blood glucose level (hyperglycemia is proportional to the severity of the injury/stress)
  
  • hyperglycemia is due to the presence of epi and glucocorticoids that stimulates liver glycogenolysis and gluconeogenesis
• low insulin levels w/ slightly increased glucose production

Question 8

describe the flow phase (aka adrenergic/cortisol)

Answer 8

• typically lasts up to 2 weeks following initial injury
• increased cardiac output begins
• increased body temp. (fever)
• increased energy expenditure (increased metabolic rate - hypermetabolic state)
• increase in circulating catecholamines, glucagon, cortisol, inflammatory cytokines
  
  • increase in the counter regulatory hormones results in insulin resistance
• insulin secretion is elevated

Question 9

describe metabolism during the flow phase (aka adrenergic/corticoid)

Answer 9

• increase in glucose production and hyperglycemia
• total body protein catabolism begins
• increase in circulating free FAs due to increased adipose tissue lipolysis
• mobilization of energy stores to facilitate wound healing

Question 10

describe the metabolic rate following critical illness

Answer 10

the metabolic rate (REE) is proportional to the severity of the illness

in prolonged starvation, there is an adaptive decrease in metabolic rate (adaptation to increase survival)

Question 11

describe the caloric requirements for an adult during the flow phase

Answer 11

Question 12

describe the glucose levels and insulin levels during the flow phase

Answer 12

• hyperglycemia
• increased insulin levels, but there is insulin resistance caused by the increased counter-regulatory hormones (epi and glucocorticoids)
  
  • increased hepatic gluconeogenesis from amino acids derived from muscle proteolysis (due to epi and glucocorticoids)
  • reduced uptake of glucose by muscle and adipose tissue (GLUT-4 is less active due to insulin resistance)

Question 13

describe lactic acidosis in critically injured patients

Answer 13

• impaired tissue oxygenation resulting in anaerobic glycolysis (if associated with a low blood flow)
• impaired blood flow also results in impairment of the Cori cycle (glucose-lactate cycle)
• lactic acidosis indicates poor prognosis

Question 14

describe carb metabolism in diabetic patients during the flow phase

Answer 14

• regulation of blood glucose level in diabetics important during hypermetabolic state but difficult to achieve due to additional insulin resistance
  
  • many pts with T2D present with hyperosmolar hyperglycemia state

Question 15

contrast carb metabolism during the flow phase of critical illness and prolonged starvation

Answer 15

Question 16

describe ketogenesis during the flow phase

Answer 16

• ketosis is not observed in patients with trauma
  
  • may be due to high levels of insulin; insulin inhibits ketogenesis
  • peripheral tissues are rapidly using ketone bodies (due to higher metabolic rate)
  • ketogenesis is inversely proportional to severity of injury

Question 17

contrast lipid metabolism in flow phase vs prolonged starvation

Answer 17

Question 18

describe protein catabolism during the flow phase

Answer 18

• protein catabolism is proportional to the severity of the illness
• in prolonged starvation there is an adaptive decrease in protein catabolism
  
  • protein sparing adaptation to increase survival
• both critical illness and starvation are states of negative nitrogen balance, but protein depletion is more severe in critical illness

Question 19

describe the mechanism of protein metabolism and excretion during the flow phase

Answer 19

• the ubiquitin-proteasome system for proteolysis in skeletal muscle cells is activated by stress/illness
• there is reduced protein synthesis and amino acid uptake by muscle
• muscle proteolysis releases aminos acids into circulation
• amino acid catabolism in liver forms ammonia which is converted to urea
• urine urea nitrogen (UNN) excretion in grams/day may be used to evaluate degree of muscle proteolysis

Question 20

there is a ____ nitrogen balance in patients during the flow phase

Answer 20

there is a negative nitrogen balance in patients during the flow phase

• intake of nitrogen <<<< output of nitrogen
• patients lose significant amounts of body tissue/muscle protein following illness

Question 21

what is the purpose of increased muscle protein catabolism?

Answer 21

• skeletal muscle is the major source of nitrogen (amino acids) following extensive injury
  
  • glutamine and alanine: majority of the released amino acids
  • amino acids are used for hepatic gluconeogenesis (C-skeleton) and the amino group is used for the formation of urea
  • amino acids are also used for maintenance of the immune system (synthesis of immunoglobulins)
  • amino acids are used for acute-phase protein synthesis by the liver

Question 22

describe acute phase response by the liver

Answer 22

• cytokines released during inflammatory process stimulate the liver to synthesize a group of proteins called acute phase proteins
  
  • synthesized in increased amount during inflammation; not specific for the inflammatory response
  • includes C-reactive protein, a1-antitrypsin, ceruloplasmin, haptoglobin

Question 23

describe how serum C-reactive protein correlates with prognosis

Answer 23

• the degree of rise of the acute phase proteins is proportional to the severity of injury
• normalization of CRP levels indicate good response to therapy and good prognosis

Question 24

contrast protein metabolism during the flow phase vs prolonged starvation

Answer 24

Question 25

describe immune modulating nutrients

Answer 25

• includes supplemental glutamine, arginine and branched chain amino acids for enhancement of immune function
  
  • glutamine is used for nucleotide synthesis in rapidly diving cells (like lymphocytes)
• inclusion of antioxidants
• omega-3 fatty acids modulate immune response

Question 26

name vitamins and minerals given during nutritional support

Answer 26

• vitamin C
  
  • facilitates wound healing (prolyl hydroxylase)
• thiamine, niacin
  
  • due to increased hypermetabolism
• zinc
  
  • maintain immune function and improve appetite
• copper
  
  • cofactor for lysyl oxidase that is required to form crosslinks in collagen and improves wound healing

Question 27

contrast ketone body synthesis in T1D vs T2D in the flow phase

Answer 27

• T1D = high ketone bodies
• T2D = not high ketone bodies but hyperosmolarity is seen

Question 28

describe the anabolic phase of recovery

Answer 28

• in the anabolic/recovery phase, there is positive nitrogen balance and build-up of tissue proteins
  
  • important to increase protein intake to allow for anabolism
• rebuilding of adipose tissue stores during this phase
• normalization of plasma glucose levels, insulin levels and tissues are sensitive to insulin