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Flashcards in Nutrition and Intensive Care Deck (28)
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1

explain the role of cytokines

  • 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

2

describe local effects of cytokines

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

3

describe system effects of cytokines

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

4

name the most important mediator of inflammation

phospholipid -> arachidonic acid -> PGE2 (prostaglandin)

5

contrast the ebb phase and the flow phase

6

describe the ebb phase

  • 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

7

describe the changes in carbohydrate metabolism during the ebb phase

  • 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

8

describe the flow phase (aka adrenergic/cortisol)

  • 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

9

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

  • 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

10

describe the metabolic rate following critical illness

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)

11

describe the caloric requirements for an adult during the flow phase

12

describe the glucose levels and insulin levels during the flow phase

  • 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)

13

describe lactic acidosis in critically injured patients

  • 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

14

describe carb metabolism in diabetic patients during the flow phase

  • 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

15

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

16

describe ketogenesis during the flow phase

  • 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

17

contrast lipid metabolism in flow phase vs prolonged starvation

18

describe protein catabolism during the flow phase

  • 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

19

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

  • 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

20

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

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

21

what is the purpose of increased muscle protein catabolism?

  • 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

22

describe acute phase response by the liver

  • 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

23

describe how serum C-reactive protein correlates with prognosis

  • 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

24

contrast protein metabolism during the flow phase vs prolonged starvation

25

describe immune modulating nutrients

  • 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

26

 name vitamins and minerals given during nutritional support

  • 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

27

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

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

28

describe the anabolic phase of recovery

  • 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