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Flashcards in Nutrition and Metabolism Deck (24):

Baseline human calorie requirements

20-25 kcal/kg/day


Baseline human protein requirement

How man kcal/g protein?


20% of caloric intake - 4 kcal/g of protein


Baseline human fat requirement?

How many kcal/g fat?

30% of caloric intake

9 kcal/g fat (most calorie dense)


Baseline carbohydrate requirement?

How man kcal/g carbs

50% of caloric intake (biggest need)

4 kcal/g carb (same as protein)


What is the Harris-Benedict equation needed to calculate BMR?

  • Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age) + 5
  • Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age) – 161


What is the percentage increase in nutritional requirements during multisystem trauma, surgery, or sepsis?

In kcal/kg/day, what nutritional guidelines are recommended for these patients?

20% - 40%

25-30 kcal/kg/d


What is the calorie and protein nutritional requirement in a burn patient?

  • Calories: 25 kcal/kg/d + (30 kcal/d × % burn)
  • Protein: 1 g/kg/d + (3 g/d × % burn)


Predicted increase in caloric requirements as a function of a stressor?

  • Elective surgery
  • Multisystem trauma
  • Sepsis
  • Burns

  • Elective surgery: 1.2 times higher
  • Multisystem trauma: 1.3 to 1.5 times higher
  • Sepsis: 1.5 to 1.8 times higher
  • Burns: 1.5 to 2.0 times higher


Biochemical changes in the critically ill/postop patient?

  • Metabolic state?
  • Protein requirement?

  • catabolic - continued proteolysis, protein requirements taken from endogenous sources if not inadequate otherwise
  • protein - 1 g/kg/d to 1.5 g/kg/d in critical illness; 2 g/kg/d 


What can be given to patients to possibly decrease proteolysis?

small amount of carbs/fat (400 kcal/d) - protein-sparing effect


In the setting of starvation, patients can develop resistance to insulin. This is caused by?

Inhibition of glucose oxidation. The body also shifts into a state of gluconeogenesis, contributing to hyperglycemia


How can you lessen the insulin resistance in the setting of starvation?

  • adequate pain control, high-carb beverage 2-3 hrs before surgery
  • monitor for hyperglycemia 
  • keep glucose 140-180 mg/dL


When is feeding recommended in a normotensive patient with intact GI tract?

early enteral feeding - 24-48 hrs

NG, OG, NJ  if necessary


When is parenteral nutrition indicated?

  • some recommend TPN at 7 days w/o ability to start enteral nutrition
  • can supplement enteral if unable to tolerate full support 
    • trophic feeds (10-30 ml/h) can help maintain GI health
  • little benefit to TPN before 7 days
  • TPN before 3 days increases infectious M&M compared to 8 days


What are the negative effects of overfeeding a patient?

  • hyperglycemia
  • hypertriglyceridemia 
  • increased RQ - weaning failure d/t increased CO2 needing to be expired causing more work for lungs


Pathophysiology of refeeding syndrome

  • sudden introduction of nutrition in a malnourished patient
  • stimulation of insulin release
  • intracellular shift of already depleted levels of PO4, K, Mg
  • decreased ATP stores cause muscle weakness 
  • electrolyte abnormalities can cause neuro/cardiac sx


What are associated side effects of parenteral nutrition?

  • electrolyte disturbances 2/2 inability of body to naturally regulate what is absorbed in gut - monitor lytes until stable formula found
  • refeeding syndrome - slowly introduce nutrition
  • liver dysfunction - steatosis 2/2 excess calories, micronutrient deficiency, lack of GI stimulation
  • line infection - requires sterile placement, place peripherally if required long-term
  • GI dysfunction - mucosal atrophy leads to loss of brush border enzymes, bacterial overgrowth, and decreased gut immunity


What equation is used to analyze the balance of anabolism and catabolism?

nitrogen balance - positive balance means requirements met

(protein intake/6.25) - (UUN+4)

UUN is 24hr urine urea nitrogen

"4" is an estimate of insensible nitrogen loss


What is the RQ and what is it used for?

respiratory quotient - measures nutrition adequacy by measuring energy expenditure

  • RQ = CO2 produced/oxygen consumed
  • RQ = 0.7 is fat utilization - ketosis and fat oxidation (starvation)
  • RQ = 0.8 is protein utilization
  • RQ = 1.0 is carb utilization - lipogenesis (overfeeding)


What lab values can be used to help assess adequate nutrition?

  • albumin - 20d t1/2
  • transferrin - 10d t1/2
  • prealbumin - 2d t1/2
  • RBP - 12hr t1/2


A 48-year-old man with a long-standing history of alcoholism and malnutrition is brought to the intensive care unit after having sustained a severe traumatic brain injury. The initial computed tomography scan of the head is consistent with diffuse axonal injury, and a neurosurgical consult leads to insertion of a ventriculostomy for monitoring intracranial pressure. Once the patient is stabilized, how do you assess and subsequently provide for the daily caloric needs?

  • calculate daily caloric requirements w/ Harris-Benedict equation
  • high caloric need 2/2 brain injury
  • early enteral feeds
  • watch for refeeding syndrome d/t malnutrition
  • watch for folate and other nutritional deficits d/t chronic alcoholism
  • watch for alcohol withdrawal
  • NGT postpyloric for enteral feeds
  • depending on neuro status, may need PEG


A 45-year-old man has sustained full-thickness burns involving 40% of his total body surface area. After appropriate resuscitation with fluids and administration of analgesia, how would you assess and provide for his nutritional requirements? What other complications can affect the general nutritional status in this patient?

  • hypermetabolic state 2/2 burns
  • will need 1.5-2x calories 
  • calories: 25 kcal/kg/d + (30 kcal/d × % burn)
  • protein: 1 g/kg/d + (3 g/d × % burn)
  • adequate nutrition will decrease risk of wound infection/sepsis



After 2 weeks on total parenteral nutrition (TPN), a trauma patient is now diagnosed with respiratory failure and is deemed to be difficult to wean from mechanical ventilation. What nutritional parameters can account for this respiratory deterioration? What adjustments can be made that can potentially benefit this patient?

  • overfeeding can cause difficulty with weaning from mechanical ventilation
  • measure resting energy expenditure w/ RQ by indirect calorimetry; if >1.0, then the patient is being overfed, subsequently producing too much CO2, and creating more work for his lungs
  • reduce calorits in TPN, and ideally transition to enteral


A 75-year-old man was brought to the emergency department from a nursing home after he was noticed to have altered mental status. After initial evaluation, it was determined that the patient was severely malnourished and was started on enteral nutrition. In 24 hours, the man had a rapid deterioration in the respiratory status, and he was intubated and brought to the surgical intensive care unit for further workup. His chest x-ray was normal. What aspects of his nutritional status might account for the deterioration of clinical status?

  • refeeding syndrome
  • prevent by assessing nutritional status and starting slowly
  • hypophosphatemia can cause respiratory weakness/failure
  • another possibility in a mentally altered patient is silent aspiration - CXR helps rule this out